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- Title
- Liquid crystal phase modulation for beam steering and near-eye displays.
- Creator
-
Lee, Yun Han, Wu, Shintson, Moharam, Jim, Likamwa, Patrick, Dong, Yajie, University of Central Florida
- Abstract / Description
-
Liquid crystal spatial phase modulator plays an important role in laser beam steering, wave-front shaping and correction, optical communication, optical computation and holography. One fundamental limitation lays in the response time of liquid crystal reorientation. To achieve fast response time, polymer-network liquid crystals are therefore proposed. By incorporating polymer network in a liquid crystal host, the response time can be reduced by a factor of 100. However, the polymer network...
Show moreLiquid crystal spatial phase modulator plays an important role in laser beam steering, wave-front shaping and correction, optical communication, optical computation and holography. One fundamental limitation lays in the response time of liquid crystal reorientation. To achieve fast response time, polymer-network liquid crystals are therefore proposed. By incorporating polymer network in a liquid crystal host, the response time can be reduced by a factor of 100. However, the polymer network introduces hysteresis, light scattering, and high voltage. The motivation for a fast-response liquid crystal phase modulator will be discussed in the first chapter. In the second chapter, we introduce our discovery that by modifying the polymer network structure with C12A, the hysteresis from the network can be eliminated, while keeping response time at the same order. In the third chapter, we introduce a new route toward fast response time. Instead of randomly generated network, we propose to utilize two-photon-polymerization method to create well-defined polymer scaffold. By introducing polymer scaffold, we demonstrated a 7-fold faster response in comparison with traditional phase modulators, while hysteresis, scattering, and high driving voltage are all eliminated. In the fourth chapter, we introduce phase modulation based on Pancharatnam-Berry (PB) phase principle. In this type of phase modulation, the defect at 2? phase reset in conventional phase modulators can be avoided. Therefore, a higher optical quality can be achieved, making them suitable for display and imaging applications. We demonstrated a fast PB lens with response time less than 1 ms, and using which we realized the first PB lens-based additive light field display to generate true (monocular) 3D content with computationally rendered images. In chapter five, we demonstrate the resolution enhancement based on pixel-shifting of fast PB gratings. By synchronizing display content with shifting pixels, we demonstrated ~2x enhanced resolution and significantly reduced screen-door artifact.In chapter six, we report our discovery of reflective polarization volume gratings (PVGs) based on self-organized liquid crystal helix. We achieved a large deflection angle ((>)50(&)deg; in glass), high diffraction efficiency ((>)95%), and unique polarization selectivity (distinction ratio (>) 100:1). A system integrating PB optical elements is described in chapter seven.Finally, we will summarize our major accomplishments in chapter eight.
Show less - Date Issued
- 2018
- Identifier
- CFE0007760, ucf:52389
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007760
- Title
- Cryogenic performance projections for ultra-small oxide-free vertical-cavity surface-emitting lasers.
- Creator
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Bayat, Mina, Deppe, Dennis, Li, Guifang, Schoenfeld, Winston, Lyakh, Arkadiy, University of Central Florida
- Abstract / Description
-
Small-sized vertical-cavity surface-emitting laser (VCSEL) may offer very low power consumption along with high reliability for cryogenic data transfer. Cryogenic data transfer has application in supercomputers and superconducting for efficient computing and also focal plane array cameras operating at 77 K, and at the lower temperature of 4 K for data extraction from superconducting circuits. A theoretical analysis is presented for 77 K and 4 K operation based on small cavity, oxide-free...
Show moreSmall-sized vertical-cavity surface-emitting laser (VCSEL) may offer very low power consumption along with high reliability for cryogenic data transfer. Cryogenic data transfer has application in supercomputers and superconducting for efficient computing and also focal plane array cameras operating at 77 K, and at the lower temperature of 4 K for data extraction from superconducting circuits. A theoretical analysis is presented for 77 K and 4 K operation based on small cavity, oxide-free VCSEL sizes of 2 to 6 (&)#181;m, that have been shown to operate efficiently at room temperature. Temperature dependent operation for optimally-designed VCSELs are studied by calculating the response of the laser at 77 K and 4 K to estimate their bias conditions needed to reach modulation speed for cryogenic optical links. The temperature influence is to decrease threshold for reducing temperature, and to increase differential gain for reducing temperature. The two effects predict very low bias currents for small cavity VCSELs to reach needed data speed for cryogenic optical data links. Projections are made for different cavity structures (half-wave cavity and full-wave cavity) shown that half-wave cavity structure has better performance. Changing the number of top-mirror pairs has also been studied to determine how cavity design impacts speed and bit energy. Our design and performance predictions paves the way for realizing highly efficient, ultra-small VCSEL arrays with applications in optical interconnects.
Show less - Date Issued
- 2019
- Identifier
- CFE0007782, ucf:52330
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007782
- Title
- Holographic optical elements for visible light applications in photo-thermo-refractive glass.
- Creator
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Kompan, Fedor, Glebov, Leonid, Schulzgen, Axel, Richardson, Kathleen, Rahman, Talat, University of Central Florida
- Abstract / Description
-
This dissertation reports on design and fabrication of various optical elements in Photo-thermo-refractive (PTR) glass. An ability to produce complex holographic optical elements (HOEs) for the visible spectral region appears very beneficial for variety of applications, however, it is limited due to photosensitivity of the glass confined within the UV region. First two parts of this dissertation present two independent approaches to the problem of holographic recording using visible radiation...
Show moreThis dissertation reports on design and fabrication of various optical elements in Photo-thermo-refractive (PTR) glass. An ability to produce complex holographic optical elements (HOEs) for the visible spectral region appears very beneficial for variety of applications, however, it is limited due to photosensitivity of the glass confined within the UV region. First two parts of this dissertation present two independent approaches to the problem of holographic recording using visible radiation. The first method involves modification of the original PTR glass rendering it photosensitive to radiation in the visible spectral region and, thus, making possible the recording of holograms in PTR glass with visible radiation. The mechanism of photoionization in this case is based on an excited state absorption upconversion process in the glass when doped with Tb3+. By contrast, the second approach uses the original Ce3+ doped PTR glass and introduces a new modified technique for hologram formation that allows for holographic recording with visible light. Complex HOEs including holographic lenses and holographic curved mirrors were fabricated in PTR glass with visible light using both techniques. The third part of the dissertation takes a step in a different direction and discusses the development of the methods for fabrication of phase masks in PTR glass. A method for relatively straightforward and inexpensive fabrication of phase masks with the aid of a Digital Micromirror Device is presented. This method enabled to produce phase masks containing complex greyscale phase distributions for generation of vortex (helical) beams. A phase mask can be holographically encoded into a transmission Bragg grating where a holographic phase mask (HPM) is formed. HPM has an advantage over a regular phase mask of being capable of multi-wavelength operation. All optical elements recorded in PTR glass preserve the advantages peculiar to VBGs recorded in PTR glass such as stability to heating and illumination with high-power laser beams.
Show less - Date Issued
- 2019
- Identifier
- CFE0007665, ucf:52480
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007665
- Title
- Imaging through Glass-air Anderson Localizing Optical Fiber.
- Creator
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Zhao, Jian, Schulzgen, Axel, Amezcua Correa, Rodrigo, Pang, Sean, Delfyett, Peter, Mafi, Arash, University of Central Florida
- Abstract / Description
-
The fiber-optic imaging system enables imaging deeply into hollow tissue tracts or organs of biological objects in a minimally invasive way, which are inaccessible to conventional microscopy. It is the key technology to visualize biological objects in biomedical research and clinical applications. The fiber-optic imaging system should be able to deliver a high-quality image to resolve the details of cell morphology in vivo and in real time with a miniaturized imaging unit. It also has to be...
Show moreThe fiber-optic imaging system enables imaging deeply into hollow tissue tracts or organs of biological objects in a minimally invasive way, which are inaccessible to conventional microscopy. It is the key technology to visualize biological objects in biomedical research and clinical applications. The fiber-optic imaging system should be able to deliver a high-quality image to resolve the details of cell morphology in vivo and in real time with a miniaturized imaging unit. It also has to be insensitive to environmental perturbations, such as mechanical bending or temperature variations. Besides, both coherent and incoherent light sources should be compatible with the imaging system. It is extremely challenging for current technologies to address all these issues simultaneously. The limitation mainly lies in the deficient stability and imaging capability of fiber-optic devices and the limited image reconstruction capability of algorithms. To address these limitations, we first develop the randomly disordered glass-air optical fiber featuring a high air-filling fraction (~28.5 %) and low loss (~1 dB per meter) at visible wavelengths. Due to the transverse Anderson localization effect, the randomly disordered structure can support thousands of modes, most of which demonstrate single-mode properties. By making use of these modes, the randomly disordered optical fiber provides a robust and low-loss imaging system which can transport images with higher quality than the best commercially available imaging fiber. We further demonstrate that deep-learning algorithm can be applied to the randomly disordered optical fiber to overcome the physical limitation of the fiber itself. At the initial stage, a laser-illuminated system is built by integrating a deep convolutional neural network with the randomly disordered optical fiber. Binary sparse objects, such as handwritten numbers and English letters, are collected, transported and reconstructed using this system. It is proved that this first deep-learning-based fiber imaging system can perform artifact-free, lensless and bending-independent imaging at variable working distances. In real-world applications, the gray-scale biological subjects have much more complicated features. To image biological tissues, we re-design the architecture of the deep convolutional neural network and apply it to a newly designed system using incoherent illumination. The improved fiber imaging system has much higher resolution and faster reconstruction speed. We show that this new system can perform video-rate, artifact-free, lensless cell imaging. The cell imaging process is also remarkably robust with regard to mechanical bending and temperature variations. In addition, this system demonstrates stronger transfer-learning capability than existed deep-learning-based fiber imaging system.
Show less - Date Issued
- 2019
- Identifier
- CFE0007746, ucf:52405
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007746
- Title
- Third-order optical nonlinearities for integrated microwave photonics applications.
- Creator
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Malinowski, Marcin, Fathpour, Sasan, Delfyett, Peter, Christodoulides, Demetrios, Lyakh, Arkadiy, University of Central Florida
- Abstract / Description
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The field of integrated photonics aims at compressing large and environmentally-sensitive opticalsystems to micron-sized circuits that can be mass-produced through existing semiconductor fabri-cation facilities. The integration of optical components on single chips is pivotal to the realizationof miniature systems with high degree of complexity. Such novel photonic chips find abundant ap-plications in optical communication, spectroscopy and signal processing. This work concentrateson...
Show moreThe field of integrated photonics aims at compressing large and environmentally-sensitive opticalsystems to micron-sized circuits that can be mass-produced through existing semiconductor fabri-cation facilities. The integration of optical components on single chips is pivotal to the realizationof miniature systems with high degree of complexity. Such novel photonic chips find abundant ap-plications in optical communication, spectroscopy and signal processing. This work concentrateson harnessing nonlinear phenomena to this avail.The first part of this dissertation discusses, both from component and system level, the developmentof a frequency comb source with a semiconductor mode-locked laser at its heart. New nonlinear de-vices for supercontinuum and second-harmonic generations are developed and their performance isassessed inside the system. Theoretical analysis of a hybrid approach with synchronously-pumpedKerr cavity is also provided. The second part of the dissertation investigates stimulated Brillouinscattering (SBS) in integrated photonics. A fully-tensorial open-source numerical tool is developedto study SBS in optical waveguides composed of crystalline materials, particularly silicon. SBS isdemonstrated in an all-silicon optical platform.
Show less - Date Issued
- 2019
- Identifier
- CFE0007674, ucf:52497
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007674
- Title
- Quantitative Line Assignment in Optical Emission Spectroscopy.
- Creator
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Chappell, Jessica, Baudelet, Matthieu, Hernandez, Florencio, Campiglia, Andres, Ni, Liqiang, Sigman, Michael, University of Central Florida
- Abstract / Description
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Quantitative elemental analysis using Optical Emission Spectroscopy (OES) starts with a high level of confidence in spectral line assignment from reference databases. Spectral interferences caused by instrumental and line broadening decrease the resolution of OES spectra creating uncertainty in the elemental profile of a sample for the first time. An approach has been developed to quantify spectral interferences for individual line assignment in OES. The algorithm calculates a statistical...
Show moreQuantitative elemental analysis using Optical Emission Spectroscopy (OES) starts with a high level of confidence in spectral line assignment from reference databases. Spectral interferences caused by instrumental and line broadening decrease the resolution of OES spectra creating uncertainty in the elemental profile of a sample for the first time. An approach has been developed to quantify spectral interferences for individual line assignment in OES. The algorithm calculates a statistical interference factor (SIF) that combines a physical understanding of plasma emission with a Bayesian analysis of the OES spectrum. It can be used on a single optical spectrum and still address individual lines. Contrary to current methods, quantification of the uncertainty in elemental profiles of OES, leads to more accurate results, higher reliability and validation of the method. The SIF algorithm was evaluated for Laser-Induced Breakdown Spectroscopy (LIBS) on samples with increasing complexity: from silicon to nickel spiked alumina to NIST standards (600 glass series and nickel-chromium alloy). The influence of the user's knowledge of the sample composition was studied and showed that for the majority of spectral lines this information is not changing the line assignment for simple compositions. Nonetheless, the amount of interference could change with this information, as expected. Variance of the SIF results for NIST glass standard was evaluated by the chi-square hypothesis test of variance showing that the results of the SIF algorithm are very reproducible.
Show less - Date Issued
- 2018
- Identifier
- CFE0007564, ucf:52575
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007564
- Title
- TOWARDS CALIBRATION OF OPTICAL FLOW OF CROWD VIDEOS USING OBSERVED TRAJECTORIES.
- Creator
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Elbadramany, Iman, Kaup, David, University of Central Florida
- Abstract / Description
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The need exists for finding a quantitative method for validating crowd simulations. One approach is to use optical flow of videos of real crowds to obtain velocities that can be used for comparison to simulations. Optical flow, in turn, needs to be calibrated to be useful. It is essential to show that optical flow velocities obtained from crowd videos can be mapped into the spatially averaged velocities of the observed trajectories of crowd members, and to quantify the extent of the...
Show moreThe need exists for finding a quantitative method for validating crowd simulations. One approach is to use optical flow of videos of real crowds to obtain velocities that can be used for comparison to simulations. Optical flow, in turn, needs to be calibrated to be useful. It is essential to show that optical flow velocities obtained from crowd videos can be mapped into the spatially averaged velocities of the observed trajectories of crowd members, and to quantify the extent of the correlation of the results. This research investigates methods to uncover the best conditions for a good correlation between optical flow and the average motion of individuals in crowd videos, with the aim that this will help in the quantitative validation of simulations. The first approach was to use a simple linear proportionality relation, with a single coefficient, alpha, between velocity vector of the optical flow and observed velocity of crowd members in a video or simulation. Since there are many variables that affect alpha, an attempt was made to find the best possible conditions for determining alpha, by varying experimental and optical flow settings. The measure of a good alpha was chosen to be that alpha does not vary excessively over a number of video frames. Best conditions of low coefficient of variation of alpha using the Lucas-Kanade optical flow algorithm were found to be when a larger aperture of 15x15 pixels was used, combined with a smaller threshold. Adequate results were found at cell size 40x40 pixels; the improvement in detecting details when smaller cells are used did not reduce the variability of alpha, and required much more computing power. Reduction in variability of alpha can be obtained by spreading the tracked location of a crowd member from a pixel into a rectangle. The Particle Image Velocimetry optical flow algorithm had better correspondence with the velocity vectors of manually tracked crowd members than results obtained using the Lukas-Kanade method. Here, also, it was found that 40x40 pixel cells were better than 15x15. A second attempt at quantifying the correlation between optical flow and actual crowd member velocities was studied using simulations. Two processes were researched, which utilized geometrical correction of the perspective distortion of the crowd videos. One process geometrically corrects the video, and then obtains optical flow data. The other obtains optical flow data from video, and then geometrically corrects the data. The results indicate that the first process worked better. Correlation was calculated between sets of data obtained from the average of twenty frames. This was found to be higher than calculating correlations between the velocities of cells in each pair of frames. An experiment was carried out to predict crowd tracks using optical flow and a calculated parameter, beta, seems to give promising results.
Show less - Date Issued
- 2011
- Identifier
- CFE0004024, ucf:49175
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004024
- Title
- INVESTIGATION OF REACTIVELY SPUTTERED BORON CARBON NITRIDE THIN FILMS.
- Creator
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Todi, Vinit, Sundaram, Kalpathy, University of Central Florida
- Abstract / Description
-
Research efforts have been focused in the development of hard and wear resistant coatings over the last few decades. These protective coatings find applications in the industry such as cutting tools, automobile and machine part etc. Various ceramic thin films like TiN, TiAlN, TiC, SiC and diamond-like carbon (DLC) are examples of the films used in above applications. However, increasing technological and industrial demands request thin films with more complicated and advanced properties. For...
Show moreResearch efforts have been focused in the development of hard and wear resistant coatings over the last few decades. These protective coatings find applications in the industry such as cutting tools, automobile and machine part etc. Various ceramic thin films like TiN, TiAlN, TiC, SiC and diamond-like carbon (DLC) are examples of the films used in above applications. However, increasing technological and industrial demands request thin films with more complicated and advanced properties. For this purpose, B-C-N ternary system which is based on carbon, boron and nitrogen which exhibit exceptional properties and attract much attention from mechanical, optical and electronic perspectives. Also, boron carbonitride (BCN) thin films contains interesting phases such as diamond, cubic BN (c-BN), hexagonal boron nitride (h-BN), B4C, [two]-C3N4. Attempts have been made to form a material with semiconducting properties between the semi metallic graphite and the insulating h-BN, or to combine the cubic phases of diamond and c-BN (BC2N heterodiamond) in order to merge the higher hardness of the diamond with the advantages of c-BN, in particular with its better chemical resistance to iron and oxygen at elevated temperatures. New microprocessor CMOS technologies require interlayer dielectric materials with lower dielectric constant than those used in current technologies to meet RC delay goals and to minimize cross-talk. Silicon oxide or fluorinated silicon oxide (SiOF) materials having dielectric constant in the range of 3.6 to 4 have been used for many technology nodes. In order to meet the aggressive RC delay goals, new technologies require dielectric materials with K<3. BCN shows promise as a low dielectric constant material with good mechanical strength suitable to be used in newer CMOS technologies. For optical applications, the deposition of BCN coatings on polymers is a promising method for protecting the polymer surface against wear and scratching. BCN films have high optical transparency and thus can be used as mask substrates for X-ray lithography. Most of the efforts from different researchers were focused to deposit cubic boron nitride and boron carbide films. Several methods of preparing boron carbon nitride films have been reported, such as chemical vapor deposition (CVD), plasma assisted CVD, pulsed laser ablation and ion beam deposition. Very limited studies could be found focusing on the effect of nitrogen incorporation into boron carbide structure by sputtering. In this work, the deposition and characterization of amorphous thin films of boron carbon nitride (BCN) is reported. The BCN thin films were deposited by radio frequency (rf) magnetron sputtering system. The BCN films were deposited by sputtering from a high purity B4C target with the incorporation of nitrogen gas in the sputtering ambient. Films of different compositions were deposited by varying the ratios of argon and nitrogen gas in the sputtering ambient. Investigation of the oxidation kinetics of these materials was performed to study high temperature compatibility of the material. Surface characterization of the deposited films was performed using X-ray photoelectron spectroscopy and optical profilometry. Studies reveal that the chemical state of the films is highly sensitive to nitrogen flow ratios during sputtering. Surface analysis shows that smooth and uniform BCN films can be produced using this technique. Carbon and nitrogen content in the films seem to be sensitive to annealing temperatures. However depth profile studies reveal certain stoichiometric compositions to be stable after high temperature anneal up to 700[degrees]C. Electrical and optical characteristics are also investigated with interesting results. The optical band gap of the films ranged from 2.0 eV - 3.1 eV and increased with N2/Ar gas flow ratio except at the highest ratio. The optical band gap showed an increasing trend when annealed at higher temperatures. The effect of deposition temperature on the optical and chemical compositions of the BCN films was also studied. The band gap increased with the deposition temperature and the films deposited at 500oC had the highest band gap. Dielectric constant was calculated from the Capacitance-Voltage curves obtained for the MOS structures with BCN as the insulating material. Aluminum was used as the top electrode and the substrate was p-type Si. Effect of N2/Ar gas flow ratio and annealing on the values of dielectric constant was studied and the dielectric constant of 2.5 was obtained for the annealed BCN films. This by far is the lowest value of dielectric constant reported for BCN film deposited by sputtering. Lastly, the future research work on the BCN films that will be carried out as a part of the dissertation is proposed.
Show less - Date Issued
- 2011
- Identifier
- CFE0004033, ucf:49181
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004033
- Title
- Ultra High Density Spectral Beam Combining By Thermal Tuning of Volume Bragg Gratings in Photo-Thermo-Refractive Glass.
- Creator
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Drachenberg, Derrek, Zeldovich, Boris, Bass, Michael, Schulzgen, Axel, Likamwa, Patrick, Glebov, Leonid, University of Central Florida
- Abstract / Description
-
High power lasers with diffraction limited beam quality are desired for many applications in defense and manufacturing. A lot of applications require laser beams at the 100 kW power level along with divergence close to the diffraction limit. The figure of merit for a beam used in such applications should be radiance which determines the laser power delivered to a remote target. One of the primary limiting factors is thermal distortion of a laser beam caused by excessive heat generated in the...
Show moreHigh power lasers with diffraction limited beam quality are desired for many applications in defense and manufacturing. A lot of applications require laser beams at the 100 kW power level along with divergence close to the diffraction limit. The figure of merit for a beam used in such applications should be radiance which determines the laser power delivered to a remote target. One of the primary limiting factors is thermal distortion of a laser beam caused by excessive heat generated in the laser media. Combination of multiple laser beams is usually considered as a method to mitigate these limitations. Spectral beam combining (SBC) by volume Bragg gratings (VBGs) is a very promising method for the future of high radiance lasers that needs to achieve 100 kW-level power. This work is dedicated to development of methods to increase spectral density of combined beams keeping their divergence at an acceptably low level.A new figure of merit for a beam combining system is proposed, the Beam Combining Factor (BCF), which makes it possible to distinguish the quality of the individual beams from the quality of beam combining. Also presented is a method of including the effect of beam divergence and spectral bandwidth on the performance of VBGs, as well as a method to optimize VBG parameters in terms of thickness and refractive index modulation for an arbitrary number of beams.A novel thermal tuning technique and apparatus is presented with which the SBC system can be tuned for peak efficiency from low to high power without the need for mechanical re-alignment. Finally, a thermally tuned SBC system with five beams, with a spectral separation between beams of 0.25 nm at a total power of 685 W is presented. The results show the highest power spectral density and highest spectral radiance of any SBC system to date. Recent demonstrations in SBC by multiplexed VBGs and the use of super Gaussian beams for beam quality improvement are also discussed.
Show less - Date Issued
- 2011
- Identifier
- CFE0004104, ucf:49089
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004104
- Title
- MARKERLESS TRACKING USING POLAR CORRELATION OF CAMERA OPTICAL FLOW.
- Creator
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Gupta, Prince, da Vitoria Lobo, Niels, University of Central Florida
- Abstract / Description
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We present a novel, real-time, markerless vision-based tracking system, employing a rigid orthogonal configuration of two pairs of opposing cameras. Our system uses optical flow over sparse features to overcome the limitation of vision-based systems that require markers or a pre-loaded model of the physical environment. We show how opposing cameras enable cancellation of common components of optical flow leading to an efficient tracking algorithm that captures five degrees of freedom...
Show moreWe present a novel, real-time, markerless vision-based tracking system, employing a rigid orthogonal configuration of two pairs of opposing cameras. Our system uses optical flow over sparse features to overcome the limitation of vision-based systems that require markers or a pre-loaded model of the physical environment. We show how opposing cameras enable cancellation of common components of optical flow leading to an efficient tracking algorithm that captures five degrees of freedom including direction of translation and angular velocity. Experiments comparing our device with an electromagnetic tracker show that its average tracking accuracy is 80% over 185 frames, and it is able to track large range motions even in outdoor settings. We also present how opposing cameras in vision-based inside-looking-out systems can be used for gesture recognition. To demonstrate our approach, we discuss three different algorithms for recovering motion parameters at different levels of complete recovery. We show how optical flow in opposing cameras can be used to recover motion parameters of the multi-camera rig. Experimental results show gesture recognition accuracy of 88.0%, 90.7% and 86.7% for our three techniques, respectively, across a set of 15 gestures.
Show less - Date Issued
- 2010
- Identifier
- CFE0003163, ucf:48611
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003163
- Title
- EXTREME ULTRAVIOLET SPECTRAL STREAK CAMERA.
- Creator
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Szilagyi, John, Richardson, Martin, University of Central Florida
- Abstract / Description
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The recent development of extreme ultraviolet (EUV) sources has increased the need for diagnostic tools, and has opened up a previously limited portion of the spectrum. With ultrafast laser systems and spectroscopy moving into shorter timescales and wavelengths, the need for nanosecond scale imaging of EUV is increasing. EUVÂÂÂÂ's high absorption has limited the number of imaging options due...
Show moreThe recent development of extreme ultraviolet (EUV) sources has increased the need for diagnostic tools, and has opened up a previously limited portion of the spectrum. With ultrafast laser systems and spectroscopy moving into shorter timescales and wavelengths, the need for nanosecond scale imaging of EUV is increasing. EUVÂÂÂÂ's high absorption has limited the number of imaging options due to the many atomic resonances in this spectrum. Currently EUV is imaged with photodiodes and X-ray CCDs. However photodiodes are limited in that they can only resolve intensity with respect to time and X-ray CCDs are limited to temporal resolution in the microsecond range. This work shows a novel approach to imaging EUV light over a nanosecond time scale, by using an EUV scintillator to convert EUV to visible light imaged by a conventional streak camera. A laser produced plasma, using a mass-limited tin based target, provided EUV light which was imaged by a grazing incidence flat field spectrometer onto a Ce:YAG scintillator. The EUV spectrum (5 nm-20 nm) provided by the spectrometer is filter by a zirconium filter and then converted by the scintillator to visible light (550 nm) which can then be imaged with conventional optics. Visible light was imaged by an electron image tube based streak camera. The streak camera converts the visible light image to an electron image using a photocathode, and sweeps the image across a recording medium. The streak camera also provides amplification and gating of the image by the means of a micro channel plate, within the image tube, to compensate for low EUV intensities. The system provides 42 ns streaked images of light with a temporal resolution of 440 ps at a repetition rate of 1 Hz. Upon calibration the EUV streak camera developed in this work will be used in future EUV development.
Show less - Date Issued
- 2010
- Identifier
- CFE0003558, ucf:48905
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003558
- Title
- High Energy, High Average Power, Picosecond Laser Systems to Drive Few-Cycle OPCPA.
- Creator
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Vaupel, Andreas, Richardson, Martin, Delfyett, Peter, Schulzgen, Axel, Shivamoggi, Bhimsen, University of Central Florida
- Abstract / Description
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The invention of chirped-pulse amplification (CPA) in 1985 led to a tremendous increase in obtainable laser pulse peak intensities. Since then, several table-top, Ti:sapphire-based CPA systems exceeding the 100 TW-level with more than 10 W average power have been developed and several systems are now commercially available. Over the last decade, the complementary technology of optical parametric chirped-pulse amplification (OPCPA) has improved in its performance to a competitive level. OPCPA...
Show moreThe invention of chirped-pulse amplification (CPA) in 1985 led to a tremendous increase in obtainable laser pulse peak intensities. Since then, several table-top, Ti:sapphire-based CPA systems exceeding the 100 TW-level with more than 10 W average power have been developed and several systems are now commercially available. Over the last decade, the complementary technology of optical parametric chirped-pulse amplification (OPCPA) has improved in its performance to a competitive level. OPCPA allows direct amplification of an almost-octave spanning bandwidth supporting few-cycle pulse durations at center wavelengths ranging from the visible to the mid-IR. The current record in peak power from a table-top OPCPA is 16 TW and the current record average power is 22 W. High energy, few-cycle pulses with stabilized carrier-envelope phase (CEP) are desired for applications such as high-harmonic generation (HHG) enabling attoscience and the generation keV-photon bursts.This dissertation conceptually, numerically and experimentally describes essential aspects of few-cycle OPCPA, and the associated pump beam generation. The main part of the conducted research was directed towards the few-cycle OPCPA facility developed in the Laser Plasma Laboratory at CREOL (University of Central Florida, USA) termed HERACLES. This facility was designed to generate few-cycle pulses in the visible with mJ-level pulse energy, W-level average power and more than 100 GW peak power. Major parts of the implementation of the HERACLES facility are presented.The pump generation beam of the HERACLES system has been improved in terms of pulse energy, average power and stability over the last years. It is based on diode-pumped, solid-state amplifiers with picosecond duration and experimental investigations are presented in detail. A robust system has been implemented producing mJ-level pulse energies with ~100 ps pulse duration at kHz repetition rates. Scaling of this system to high power ((>)30 W) and high peak power (50-MW-level) as well as ultra-high pulse energy ((>)160 mJ) is presented. The latter investigation resulted in the design of an ultra-high energy system for OPCPA pumping. Following this, a new OPCPA facility was designed termed PhaSTHEUS, which is anticipated to reach ultra-high intensities.Another research effort was conducted at CELIA (Univerist(&)#233; de Bordeaux 1, France) and aimed towards a previously unexplored operational regime of OPCPA with ultra-high repetition rates (10 MHz) and high average power. A supercontinuum seed beam generation has been established with an output ranging from 1.3 to 1.9 ?m and few ps duration. The pump beam generation has been implemented based on rod-type fiber amplifiers producing more than 37 W average power and 370 kW peak power. The utility of this system as an OPCPA pump laser is presented along with the OPA design.The discussed systems operate in radically different regimes in terms of peak power, average power, and repetition rate. The anticipated OPCPA systems with few-cycle duration enable a wide range of novel experimental studies in attoscience, ultrafast materials processing, filamentation, LIBS and coherent control.
Show less - Date Issued
- 2013
- Identifier
- CFE0004952, ucf:49570
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004952
- Title
- GABOR DOMAIN OPTICAL COHERENCE MICROSCOPY.
- Creator
-
Murali, Supraja, Rolland, Jannick, University of Central Florida
- Abstract / Description
-
Time domain Optical Coherence Tomography (TD-OCT), first reported in 1991, makes use of the low temporal coherence properties of a NIR broadband laser to create depth sectioning of up to 2mm under the surface using optical interferometry and point to point scanning. Prior and ongoing work in OCT in the research community has concentrated on improving axial resolution through the development of broadband sources and speed of image acquisition through new techniques such as Spectral domain OCT ...
Show moreTime domain Optical Coherence Tomography (TD-OCT), first reported in 1991, makes use of the low temporal coherence properties of a NIR broadband laser to create depth sectioning of up to 2mm under the surface using optical interferometry and point to point scanning. Prior and ongoing work in OCT in the research community has concentrated on improving axial resolution through the development of broadband sources and speed of image acquisition through new techniques such as Spectral domain OCT (SD-OCT). In SD-OCT, an entire depth scan is acquired at once with a low numerical aperture (NA) objective lens focused at a fixed point within the sample. In this imaging geometry, a longer depth of focus is achieved at the expense of lateral resolution, which is typically limited to 10 to 20 µm. Optical Coherence Microscopy (OCM), introduced in 1994, combined the advantages of high axial resolution obtained in OCT with high lateral resolution obtained by increasing the NA of the microscope placed in the sample arm. However, OCM presented trade-offs caused by the inverse quadratic relationship between the NA and the DOF of the optics used. For applications requiring high lateral resolution, such as cancer diagnostics, several solutions have been proposed including the periodic manual re-focusing of the objective lens in the time domain as well as the spectral domain C-mode configuration in order to overcome the loss in lateral resolution outside the DOF. In this research, we report for the first time, high speed, sub-cellular imaging (lateral resolution of 2 µm) in OCM using a Gabor domain image processing algorithm with a custom designed and fabricated dynamic focus microscope interfaced to a Ti:Sa femtosecond laser centered at 800 nm within an SD-OCM configuration. It is envisioned that this technology will provide a non-invasive replacement for the current practice of multiple biopsies for skin cancer diagnosis. The research reported here presents three important advances to this technology all of which have been demonstrated in full functional hardware conceived and built during the course of this research. First, it has been demonstrated that the coherence gate created by the femtosecond laser can be coupled into a scanning optical microscope using optical design methods to include liquid lens technology that enables scanning below the surface of skin with no moving parts and at high resolution throughout a 2×2×2 mm imaging cube. Second, the integration the variable-focus liquid lens technology within a fixed-optics microscope custom optical design helped increase the working NA by an order of magnitude over the limitation imposed by the liquid lens alone. Thus, this design has enabled homogenous axial and lateral resolution at the micron-level (i.e., 2 µm) while imaging in the spectral domain, and still maintaining in vivo speeds. The latest images in biological specimens clearly demonstrate sub-cellular resolution in all dimensions throughout the imaging volume. Third, this new modality for data collection has been integrated with an automated Gabor domain image registration and fusion algorithm to provide full resolution images across the data cube in real-time. We refer to this overall OCM method as Gabor domain OCM (GD-OCM). These advantages place GD-OCM in a unique position with respect to the diagnosis of cancer, because when fully developed, it promises to enable fast and accurate screening for early symptoms that could lead to prevention. The next step for this technology is to apply it directly, in a clinical environment. This step is underway and is expected to be reported by the next generation of researchers within this group.
Show less - Date Issued
- 2009
- Identifier
- CFE0002771, ucf:48137
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002771
- Title
- NEAR-FIELD OPTICAL INTERACTIONS AND APPLICATIONS.
- Creator
-
Haefner, David, Dogariu, Aristide, University of Central Florida
- Abstract / Description
-
The propagation symmetry of electromagnetic fields is affected by encounters with material systems. The effects of such interactions, for example, modifications of intensity, phase, polarization, angular spectrum, frequency, etc. can be used to obtain information about the material system. However, the propagation of electromagnetic waves imposes a fundamental limit to the length scales over which the material properties can be observed. In the realm of near-field optics, this limitation is...
Show moreThe propagation symmetry of electromagnetic fields is affected by encounters with material systems. The effects of such interactions, for example, modifications of intensity, phase, polarization, angular spectrum, frequency, etc. can be used to obtain information about the material system. However, the propagation of electromagnetic waves imposes a fundamental limit to the length scales over which the material properties can be observed. In the realm of near-field optics, this limitation is overcome only through a secondary interaction that couples the high-spatial-frequency (but non-propagating) field components to propagating waves that can be detected. The available information depends intrinsically on this secondary interaction, which constitutes the topic of this study. Quantitative measurements of material properties can be performed only by controlling the subtle characteristics of these processes. This dissertation discusses situations where the effects of near-field interactions can be (i) neglected in certain passive testing techniques, (ii) exploited for active probing of static or dynamic systems, or (iii) statistically isolated when considering optically inhomogeneous materials. This dissertation presents novel theoretical developments, experimental measurements, and numerical results that elucidate the vectorial aspects of the interaction between light and nano-structured material for use in sensing applications.
Show less - Date Issued
- 2010
- Identifier
- CFE0003095, ucf:48318
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003095
- Title
- ANALYSIS AND DESIGN OF WIDE-ANGLE FOVEATED OPTICAL SYSTEMS.
- Creator
-
Curatu, George, Harvey, James, University of Central Florida
- Abstract / Description
-
The development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and...
Show moreThe development of compact imaging systems capable of transmitting high-resolution images in real-time while covering a wide field-of-view (FOV) is critical in a variety of military and civilian applications: surveillance, threat detection, target acquisition, tracking, remote operation of unmanned vehicles, etc. Recently, optical foveated imaging using liquid crystal (LC) spatial light modulators (SLM) has received considerable attention as a potential approach to reducing size and complexity in fast wide-angle lenses. The fundamental concept behind optical foveated imaging is reducing the number of elements in a fast wide-angle lens by placing a phase SLM at the pupil stop to dynamically compensate aberrations left uncorrected by the optical design. In the recent years, considerable research and development has been conducted in the field of optical foveated imaging based on the LC SLM technology, and several foveated optical systems (FOS) prototypes have been built. However, most research has been focused so far on the experimental demonstration of the basic concept using off the shelf components, without much concern for the practicality or the optical performance of the systems. Published results quantify only the aberration correction capabilities of the FOS, often claiming diffraction limited performance at the region of interest (ROI). However, these results have continually overlooked diffraction effects on the zero-order efficiency and the image quality. The research work presented in this dissertation covers the methods and results of a detailed theoretical research study on the diffraction analysis, image quality, design, and optimization of fast wide-angle FOSs based on the current transmissive LC SLM technology. The amplitude and phase diffraction effects caused by the pixelated aperture of the SLM are explained and quantified, revealing fundamental limitations imposed by the current transmissive LC SLM technology. As a part of this study, five different fast wide-angle lens designs that can be used to build practical FOSs were developed, revealing additional challenges specific to the optical design of fast wide-angle systems, such as controlling the relative illumination, distortion, and distribution of aberrations across a wide FOV. One of the lens design examples was chosen as a study case to demonstrate the design, analysis, and optimization of a practical wide-angle FOS based on the current state-of-the-art transmissive LC SLM technology. The effects of fabrication and assembly tolerances on the image quality of fast wide-angle FOSs were also investigated, revealing the sensitivity of these fast well-corrected optical systems to manufacturing errors. The theoretical study presented in this dissertation sets fundamental analysis, design, and optimization guidelines for future developments in fast wide-angle FOSs based on transmissive SLM devices.
Show less - Date Issued
- 2009
- Identifier
- CFE0002584, ucf:48254
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002584
- Title
- The Consequences of a Reduced Superlattice Thickness on Quantum Cascade LASER Performance.
- Creator
-
Figueiredo, Pedro, Lyakh, Arkadiy, Peale, Robert, Klemm, Richard, Fathpour, Sasan, University of Central Florida
- Abstract / Description
-
Coherent infrared radiation sources are essential for the operability of a wide range of scientific, industrial, military and commercial systems. The importance of the mid-infrared spectral region cannot be understated. Numerous molecules have some vibrational band in this range, allowing for identification of species by means of absorption, emission or some other form of spectroscopy. As such, spectroscopy alone has numerous applications ranging from industrial process control to disease...
Show moreCoherent infrared radiation sources are essential for the operability of a wide range of scientific, industrial, military and commercial systems. The importance of the mid-infrared spectral region cannot be understated. Numerous molecules have some vibrational band in this range, allowing for identification of species by means of absorption, emission or some other form of spectroscopy. As such, spectroscopy alone has numerous applications ranging from industrial process control to disease diagnosis utilizing breath analysis. However, despite the discovery of the LASER in the 60s, to this day the amount of coherent sources in this range is limited. It is for this reason that the quantum cascade laser has gained such momentum over the past 23 years.Quantum Cascade LASERS (QCL) are semiconductor LASERS which are based on the principle of bandgap engineering. This incredible technique is a testament to the technological maturity of the semiconductor industry. It has been demonstrated that by having precise control of individual material composition (band gap control), thicknesses on the order of monolayers, and doping levels for each individual layer in a superlattice, we have unprecedented flexibility in designing a LASER or detector in the infrared. And although the technology has matured since it's discovery, there still remain fundamental limitations on device performance. In particular, active region overheating limits QCL performance in a high duty cycle mode of operation.In this dissertation, along with general discussion on the background of the QCL, we propose a solution of where by limiting the growth of the superlattice to a fraction of typical devices, we allow for reduction of the average superlattice temperature under full operational conditions. The consequences of this reduction are explored in theory, experiment and system level applications.
Show less - Date Issued
- 2017
- Identifier
- CFE0006592, ucf:51273
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006592
- Title
- Nanoscale Control of Gap-plasmon Enhanced Optical Processes.
- Creator
-
Lumdee, Chatdanai, Kik, Pieter, Dogariu, Aristide, Kuebler, Stephen, Huo, Qun, University of Central Florida
- Abstract / Description
-
Surface plasmon resonances of metal nanostructures have been studied intensely in recent years. The strong plasmon-mediated electric field enhancement and field confinement well beyond the diffraction limit has been demonstrated to improve the performance of optical devices including ultrasensitive sensors, light emitters, and optical absorbers. A plasmon resonance mode of particular recent interest is the gap plasmon resonance that occurs on closely spaced metallic structures. In contrast to...
Show moreSurface plasmon resonances of metal nanostructures have been studied intensely in recent years. The strong plasmon-mediated electric field enhancement and field confinement well beyond the diffraction limit has been demonstrated to improve the performance of optical devices including ultrasensitive sensors, light emitters, and optical absorbers. A plasmon resonance mode of particular recent interest is the gap plasmon resonance that occurs on closely spaced metallic structures. In contrast to plasmon resonances supported by isolated metal nanostructures, coupled nanostructures provide additional spectral and spatial control over the plasmon resonance response. For example, the resonance frequencies of metal nanoparticle dimers depend strongly on the gap size between the nanoparticles. Gap plasmons can produce local electric field enhancement factors that are several orders of magnitude stronger and more confined than surface plasmon resonances of isolated plasmonic nanospheres. The reliance of gap plasmons on few-nanometer separation between nanostructures makes it difficult to prepare gap-plasmon supporting structures with predictable resonance frequency and field enhancement. A structure that avoids this challenge is the film-coupled nanoparticle (NP). Similar to nanoparticle dimers, a nanoparticle on a supporting metallic film (or NP-on-a-mirror) can offer a strong coupling between the particle and its local environment, in this case the supporting film instead of adjacent nanoparticles, enabling strongly confined gap-plasmon modes. The NP-on-a-mirror geometry has been shown to produce reproducible gap plasmon resonances in a chemically and thermally robust, easy to fabricate structure. In this Thesis, we first present a scheme for controlling the gap plasmon resonance frequency of single gold nanoparticles using aluminum oxide coated metal films. We demonstrate experimentally and numerically that the gap-plasmon resonance of single gold nanoparticles can be tuned throughout the visible range by controlling the aluminum oxide thickness via anodization. In a separate study of Au NP on Al2O3 coated gold films it is shown that the oxide coating improves the stability of the structure under intense laser irradiation. An combined experimental and numerical analysis of the spectral response of Au NP on rough Au films shows that a film roughness of a few nanometer can affect the gap plasmon resonance in the absence of an oxide spacer layer. A photoluminescence study of single gold nanoparticles on an Al2O3 coated gold film shows that the gap-plasmon resonance of this type of plasmonic structure can increase gold photoluminescence by more than four orders of magnitude. Related numerical simulations reveal that the local photoluminescence enhancement of a gold nanoparticle on an Al2O3 coated gold film can be as high as one million near the particle-film junction. Finally, a new plasmonic sensing element was proposed based on our findings in the previous chapters. This proposed hole-in-one structure offers several attractive features including an easily optically accessible gap plasmon mode, while maintaining a relatively simple fabrication method. Taken together, the research presented in this Thesis demonstrates how the resonance frequency, field enhancement, mode polarization, structural stability, and structure reliability can be controlled at the nanoscale. The knowledge gained in the course of this work could lead to further development of nanophotonic devices that utilize extremely confined optical fields and precisely controlled resonance frequencies.
Show less - Date Issued
- 2015
- Identifier
- CFE0005972, ucf:50772
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005972
- Title
- Fabrication and Characterization of Spatially-Variant Self-Collimating Photonic Crystals.
- Creator
-
Digaum, Jennefir, Kuebler, Stephen, Kik, Pieter, Schoenfeld, Winston, Likamwa, Patrick, Gesquiere, Andre, University of Central Florida
- Abstract / Description
-
Spatially-variant photonic crystals (SVPCs) created using materials having a low refractive index are shown to be capable of abruptly controlling light beams with high polarization selectivity. SVPCs are photonic crystals for which the orientation of the unit cell is controllably varied throughout the lattice to control the flow of light. Multi-photon lithography in a photo polymer was used to fabricate three-dimensional SVPCs that direct the flow of light around a 90 degree bend. The optical...
Show moreSpatially-variant photonic crystals (SVPCs) created using materials having a low refractive index are shown to be capable of abruptly controlling light beams with high polarization selectivity. SVPCs are photonic crystals for which the orientation of the unit cell is controllably varied throughout the lattice to control the flow of light. Multi-photon lithography in a photo polymer was used to fabricate three-dimensional SVPCs that direct the flow of light around a 90 degree bend. The optical performance of the SVPCs was characterized using a scanning optical-fiber system that introduced light onto the input face of a structure and measured the intensity of light emanating from the output faces.As a proof-of-concept, SVPCs that can bend a beam at a wavelength of ?0 = 2.94 ?m were fabricated in the photo-polymer SU-8. The SVPCs were shown to direct infrared light of one polarization through a sharp bend, while the other polarization propagated straight through the SVPC, when the volumetric fill-factor is near 50%. The peak-to-peak ratio of intensities of the bent- and straight-through beams was 8:1, and a power efficiency of 8% was achieved. The low efficiency is attributed to optical absorption in SU-8 at ?0 = 2.94 ?m.SVPCs that can bend a beam at telecommunications wavelengths near ?0 = 1.55 ?m were fabricated by multi-photon lithography in the photo-polymer IP-Dip. IP-Dip was chosen over SU 8 to enable fabrication of finer features, as are needed for an SVPC scaled in size to operate at shorter wavelengths. Experimental characterization shows that these particular SVPCs provide effective control of the vertically polarized beam at ?0 = 1.55 ?m, when the volumetric fill-factor is around 46%. The beam bending peak efficiency was found to be 52.5% with a peak-to-peak ratio between the bent- and straight-through beams of 78.7. Additionally, these SVPCs can bend a light beam with a broad bandwidth of 153 nm that encompasses both the C- and S-bands of the telecommunications window. Furthermore, the SVPCs have high tolerance to misalignment, in which an offset of the input beam by as much as 6 ?m causes the beam-bending efficiency to drop no more than 50%. Finally, it is shown that these particular SVPCs can bend beams without significantly distorting the mode profile. This work introduces a new scheme for controlling light that should be useful for integrated photonics.The penultimate chapter discusses nonlinear phenomena that were observed during the optical characterization of the SVPCs using a high peak-power amplified femtosecond laser system. The first of these effects is referred to as "super-collimation", in which the beam bending peak efficiency of certain SVPCs increases with input intensity, reaching as high as 68%. The second effect pertains to nonlinear imaging of light at ?0 = 1.55 ?m scattered from an SVPC and detected using a silicon-CCD camera. This effect enables beam bending within the device to be imaged in real time. The dissertation concludes with an outlook for SVPCs, discussing potential applications and challenges that must be addressed to advance their use in photonics.
Show less - Date Issued
- 2016
- Identifier
- CFE0006527, ucf:51371
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006527
- Title
- Implementation of Optical Interferometry and Spectral Reflectometry for High Fidelity Thin Film Measurements.
- Creator
-
Arends-Rodriguez, Armando, Putnam, Shawn, Chow, Louis, Kauffman, Jeffrey, University of Central Florida
- Abstract / Description
-
An in-house reflectometer/interferometer has been built to investigate the varying curvature and thickness profiles in the contact line region of air, acetone, iso-octane, ethanol, and water on various types of substrates. Light intensity measurements were obtained using our reflectometer/interferomter and then analyzed in MATLAB to produce thickness and curvature profiles. The apparatus is based on the principle of a reflectometer, consisting of different optical elements, probe, light...
Show moreAn in-house reflectometer/interferometer has been built to investigate the varying curvature and thickness profiles in the contact line region of air, acetone, iso-octane, ethanol, and water on various types of substrates. Light intensity measurements were obtained using our reflectometer/interferomter and then analyzed in MATLAB to produce thickness and curvature profiles. The apparatus is based on the principle of a reflectometer, consisting of different optical elements, probe, light source, and spectrometer. Our reflectometer/interferomter takes measurements in the UV-Vis-IR range (200nm-1000nm). This range is achieved by using a light source that has both a deuterium light (190nm-800nm), a tungsten halogen light (400nm-1100nm), a Metal-Core Printed Circuit Board LED (800nm-1000nm) and a Metal-Core Printed Circuit board cold white LED (400nm-800nm, 6500 K). A UV-VIS-IR spectrometer reads the light response after light is focused on the region of interest. Then a CCD camera (2448x2048) records the profiles for image analyzing interferometry. The readings were then validated based on results in the literature and studies with cylindrical lens samples.
Show less - Date Issued
- 2017
- Identifier
- CFE0006559, ucf:51328
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006559
- Title
- Noise, Stability, and Linewidth Performance of 10-GHz Optical Frequency Combs Generated from the Nested Cavity Architecture.
- Creator
-
Bagnell, Kristina, Delfyett, Peter, Likamwa, Patrick, Schulzgen, Axel, DeSalvo, Richard, University of Central Florida
- Abstract / Description
-
Optical frequency combs with wide mode spacing and low timing jitter are relied upon for both time domain and frequency domain applications. It has been previously demonstrated that surrounding a low-Q semiconductor laser chip with a long external fiber cavity and inserting a high finesse Fabry(-)P(&)#233;rot etalon into this cavity can produce a mode-locked laser with the desired high repetition rate and narrow optical mode linewidths which are of benefit to applications like photonic analog...
Show moreOptical frequency combs with wide mode spacing and low timing jitter are relied upon for both time domain and frequency domain applications. It has been previously demonstrated that surrounding a low-Q semiconductor laser chip with a long external fiber cavity and inserting a high finesse Fabry(-)P(&)#233;rot etalon into this cavity can produce a mode-locked laser with the desired high repetition rate and narrow optical mode linewidths which are of benefit to applications like photonic analog-to-digital conversion and astronomical spectrograph calibration. With this nested cavity architecture, the quality factor of the resonator is effectively determined by the product of the individual quality factors of the long fiber cavity and the short etalon cavity. Passive cavity Q and intracavity power both influence mode-locked laser mode linewidth, optical frequency stability, and the phase noise of the photodetected output. The nested cavity architecture has been demonstrated at 10-GHz mode spacing a few times with increasing etalon finesse and once with a high saturation power semiconductor gain medium to increase intracavity power. No one system has been fully characterized for long term optical frequency stability, phase noise and timing jitter, and optical mode linewidth. As a result, the trade-offs involved with advancing any one element (e.g. increasing cavity Q by adding fiber length and maintaining a broad spectral region of low dispersion for broad-bandwidth operation) have not been fully examined. In this work, three cavity elements are identified for study to influence cavity Q, effective noise spur suppression, and intracavity power, and the trade-offs of pushing those parameters to new limits are experimentally demonstrated. In the process, we also demonstrate nested cavity systems with fractional frequency instability on the order of 10^-13, timing jitter as low as 20 fs, and Hz-level linewidths.
Show less - Date Issued
- 2017
- Identifier
- CFE0006717, ucf:51883
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006717
