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- Title
- ULTRASHORT, HIGH POWER, AND ULTRALOW NOISE MODE-LOCKED OPTICAL PULSE GENERATION USING QUANTUM-DOT SEMICONDUCTOR LASERS.
- Creator
-
Choi, Myoung-Taek, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
This dissertation explores various aspects and potential of optical pulse generation based on active, passive, and hybrid mode-locked quantum dot semiconductor lasers with target applications such as optical interconnect and high speed signal processing. Design guidelines are developed for the single mode operation with suppressed reflection from waveguide discontinuities. The device fabrication procedure is explained, followed by characteristics of FP laser, SOA, and monolithic two-section...
Show moreThis dissertation explores various aspects and potential of optical pulse generation based on active, passive, and hybrid mode-locked quantum dot semiconductor lasers with target applications such as optical interconnect and high speed signal processing. Design guidelines are developed for the single mode operation with suppressed reflection from waveguide discontinuities. The device fabrication procedure is explained, followed by characteristics of FP laser, SOA, and monolithic two-section devices. Short pulse generation from an external cavity mode-locked QD two-section diode laser is studied. High quality, sub-picosecond (960 fs), high peak power (1.2 W) pulse trains are obtained. The sign and magnitude of pulse chirp were measured for the first time. The role of the self-phase modulation and the linewidth enhancement factor in QD mode-locked lasers is addressed. The noise performance of two-section mode-locked lasers and a SOA-based ring laser was investigated. Significant reduction of the timing jitter under hybrid mode-locked operation was achieved owing to more than one order of magnitude reduction of the linewidth in QD gain media. Ultralow phase noise performance (integrated timing jitter of a few fs at a 10 GHz repetition rate) was demonstrated from an actively mode-locked unidirectional ring laser. These results show that quantum dot mode-locked lasers are strong competitors to conventional semiconductor lasers in noise performance. Finally we demonstrated an opto-electronic oscillator (OEO) and coupled opto-electronic oscillators (COEO) which have the potential for both high purity microwave and low noise optical pulse generation. The phase noise of the COEO is measured by the photonic delay line frequency discriminator method. Based on this study we discuss the prospects of the COEO as a low noise optical pulse source.
Show less - Date Issued
- 2006
- Identifier
- CFE0001410, ucf:47068
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001410
- Title
- EXTERNAL CAVITY MULTIWAVELENGTH SEMICONDUCTOR MODE-LOCKED LASER GAIN DYNAMICS.
- Creator
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Archundia-Berra, Luis, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
External cavity semiconductor mode-locked lasers can produce pulses of a few picoseconds. The pulses from these lasers are inherently chirped with a predominant linear chirp component that can be compensated resulting in sub-picosecond pulses. External cavity semiconductor mode-locked lasers can be configured as multiwavelength pulse sources and are good candidates for time and wavelength division multiplexing applications. The gain medium in external cavity semiconductor mode-locked lasers...
Show moreExternal cavity semiconductor mode-locked lasers can produce pulses of a few picoseconds. The pulses from these lasers are inherently chirped with a predominant linear chirp component that can be compensated resulting in sub-picosecond pulses. External cavity semiconductor mode-locked lasers can be configured as multiwavelength pulse sources and are good candidates for time and wavelength division multiplexing applications. The gain medium in external cavity semiconductor mode-locked lasers is a semiconductor optical amplifier (SOA), and passive and hybrid mode-locked operation are achieved by the introduction of a saturable absorber (SA) in the laser cavity. Pump-probe techniques were used to measure the intracavity absorption dynamics of a SA in an external cavity semiconductor mode-locked laser and the gain dynamics of a SOA for the amplification of diverse pulses. The SOA gain dynamics measurements include the amplification of 750 fs pulses, 6.5 ps pulses, multiwavelength pulses and the intracavity gain dynamics of an external cavity multiwavelength semiconductor mode-locked laser. The experimental results show how the inherent chirp on pulses from external cavity semiconductor mode-locked lasers results in a slow gain depletion without significant fast gain dynamics. In the multiwavelength operation regime of these lasers, the chirp broadens the temporal pulse profile and decreases the temporal beating resulting from the phase correlation among wavelength channels. This results in a slow gain depletion mitigating nonlinearities and gain competition among wavelength channels in the SOA supporting the multiwavelength operation of the laser. Numerical simulations support the experimental results.
Show less - Date Issued
- 2006
- Identifier
- CFE0001359, ucf:46984
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001359
- Title
- HIGH POWER MODE-LOCKED SEMICONDUCTOR LASERS AND THEIR APPLICATIONS.
- Creator
-
Lee, Shinwook, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
In this dissertation, a novel semiconductor mode-locked oscillator which is an extension of eXtreme Chirped Pulse Amplification (XCPA) is investigated. An eXtreme Chirped Pulse Oscillator (XCPO) implemented with a Theta cavity also based on a semiconductor gain is presented for generating more than 30ns frequency-swept pulses with more than 100pJ of pulse energy and 3.6ps compressed pulses directly from the oscillator. The XCPO shows the two distinct characteristics which are the scalability...
Show moreIn this dissertation, a novel semiconductor mode-locked oscillator which is an extension of eXtreme Chirped Pulse Amplification (XCPA) is investigated. An eXtreme Chirped Pulse Oscillator (XCPO) implemented with a Theta cavity also based on a semiconductor gain is presented for generating more than 30ns frequency-swept pulses with more than 100pJ of pulse energy and 3.6ps compressed pulses directly from the oscillator. The XCPO shows the two distinct characteristics which are the scalability of the output energy and the mode-locked spectrum with respect to repetition rate. The laser cavity design allows for low repetition rate operation <100MHz. The cavity significantly reduces nonlinear carrier dynamics, integrated self phase modulation (SPM), and fast gain recovery in a Semiconductor optical Amplifier (SOA). Secondly, a functional device, called a Grating Coupled Surface Emitting Laser (GCSEL) is investigated. For the first time, passive and hybrid mode-locking of a GCSEL is achieved by using saturable absorption in the passive section of GCSEL. To verify the present limitation of the GCSEL for passive and hybrid mode-locking, a dispersion matched cavity is explored. In addition, a Grating Coupled surface emitting Semiconductor Optical Amplifier (GCSOA) is also investigated to achieve high energy pulse. An energy extraction experiment for GCSOA using stretched pulses generated from the colliding pulse semiconductor mode-locked laser via a chirped fiber bragg grating, which exploits the XCPA advantages is also demonstrated. Finally, passive optical cavity amplification using an enhancement cavity is presented. In order to achieve the interferometric stability, the Hänsch-Couillaud Method is employed to stabilize the passive optical cavity. The astigmatism-free optical cavity employing an acousto-optic modulator (AOM) is designed and demonstrated. In the passive optical cavity, a 7.2 of amplification factor is achieved with a 50 KHz dumping rate.
Show less - Date Issued
- 2008
- Identifier
- CFE0002093, ucf:47555
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002093
- Title
- HIGH-SPEED MODELOCKED SEMICONDUCTOR LASERS AND APPLICATIONS IN COHERENT PHOTONIC SYSTEMS.
- Creator
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Lee, Wangkuen, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
1.55-µm high-speed modelocked semiconductor lasers are theoretically and experimentally studied for various coherent photonic system applications. The modelocked semiconductor lasers (MSLs) are designed with high-speed (>5 GHz) external cavity configurations utilizing monolithic two-section curved semiconductor optical amplifiers. By exploiting the saturable absorber section of the monolithic device, passive or hybrid mode-locking techniques are used to generate short optical pulses with...
Show more1.55-µm high-speed modelocked semiconductor lasers are theoretically and experimentally studied for various coherent photonic system applications. The modelocked semiconductor lasers (MSLs) are designed with high-speed (>5 GHz) external cavity configurations utilizing monolithic two-section curved semiconductor optical amplifiers. By exploiting the saturable absorber section of the monolithic device, passive or hybrid mode-locking techniques are used to generate short optical pulses with broadband optical frequency combs. Laser frequency stability is improved by applying the Pound-Drever-Hall (PDH) frequency stabilization technique to the MSLs. The improved laser performance after the frequency stabilization (a frequency drifting of less than 350 MHz), is extensively studied with respect to the laser linewidth (~ 3 MHz), the relative intensity noise (RIN) (< -150 dB/Hz), as well as the modal RIN (~ 3 dB reduction). MSL to MSL, and tunable laser to MSL synchronization is demonstrated by using a dual-mode injection technique and a modulation sideband injection technique, respectively. Dynamic locking behavior and locking bandwidth are experimentally and theoretically studied. Stable laser synchronization between two MSLs is demonstrated with an injection seed power on the order of a few microwatt. Several coherent heterodyne detections based on the synchronized MSL systems are demonstrated for applications in microwave photonic links and ultra-dense wavelength division multiplexing (UD-WDM) system. In addition, efficient coherent homodyne balanced receivers based on synchronized MSLs are developed and demonstrated for a spectrally phase-encoded optical CDMA (SPE-OCDMA) system.
Show less - Date Issued
- 2007
- Identifier
- CFE0001703, ucf:47326
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001703
- Title
- STABLE OPTICAL FREQUENCY COMB GENERATION AND APPLICATIONS IN ARBITRARY WAVEFORM GENERATION, SIGNAL PROCESSING AND OPTICAL DATA MINING.
- Creator
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Ozharar, Sarper, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
This thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked...
Show moreThis thesis focuses on the generation and applications of stable optical frequency combs. Optical frequency combs are defined as equally spaced optical frequencies with a fixed phase relation among themselves. The conventional source of optical frequency combs is the optical spectrum of the modelocked lasers. In this work, we investigated alternative methods for optical comb generation, such as dual sine wave phase modulation, which is more practical and cost effective compared to modelocked lasers stabilized to a reference. Incorporating these comblines, we have generated tunable RF tones using the serrodyne technique. The tuning range was ±1 MHz, limited by the electronic waveform generator, and the RF carrier frequency is limited by the bandwidth of the photodetector. Similarly, using parabolic phase modulation together with time division multiplexing, RF chirp extension has been realized. Another application of the optical frequency combs studied in this thesis is real time data mining in a bit stream. A novel optoelectronic logic gate has been developed for this application and used to detect an 8 bit long target pattern. Also another approach based on orthogonal Hadamard codes have been proposed and explained in detail. Also novel intracavity modulation schemes have been investigated and applied for various applications such as a) improving rational harmonic modelocking for repetition rate multiplication and pulse to pulse amplitude equalization, b) frequency skewed pulse generation for ranging and c) intracavity active phase modulation in amplitude modulated modelocked lasers for supermode noise spur suppression and integrated jitter reduction. The thesis concludes with comments on the future work and next steps to improve some of the results presented in this work.
Show less - Date Issued
- 2008
- Identifier
- CFE0002388, ucf:47744
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002388
- Title
- DISPERSION-MANAGED BREATHING-MODE SEMICONDUCTOR MODE-LOCKED RING LASER: EXPERIMENTAL STUDY, NUMERICAL SIMULATIONS AND APPLICATIONS.
- Creator
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Resan, Bojan, Delfyett, Peter J., University of Central Florida
- Abstract / Description
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A novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching...
Show moreA novel dispersion-managed breathing-mode semiconductor mode-locked ring laser is developed. The "breathing-mode" designation derives from the fact that intracavity pulses are alternately stretched and compressed as they circulate around the ring resonator. The pulses are stretched before entering the semiconductor gain medium to minimize the detrimental strong integrating self-phase modulation and to enable efficient pulse amplification. Subsequently compressed pulses facilitate bleaching the semiconductor saturable absorber. The intracavity pulse compression ratio is higher than 50. Down chirping when compared to up chirping allows broader mode-locked spectra and shorter pulse generation owing to temporal and spectral semiconductor gain dynamics. Pulses as short as 185 fs, with a peak power of ~230 w, and a focused intensity of ~4.6 gw/cm2 are generated by linear down chirp compensation and characterized by shg-frog method. To our knowledge, this is the highest peak power and the shortest pulse generation from an electrically pumped all-semiconductor system. The very good agreement between the simulated and the measured results verifies our understanding and ability to control the physical mechanisms involved in the pulse shaping within the ring cavity. Application trends such as continuum generation via a photonic crystal fiber, two-photon fluorescence imaging, and ultrafast pulse source for pump-probe experiments are demonstrated.
Show less - Date Issued
- 2004
- Identifier
- CFE0000176, ucf:46155
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000176
- Title
- DIRECT NONLINEAR OPTICS MEASUREMENTS OF RAMAN GAIN IN BULK GLASSES AND ESTIMATES OF FIBER PERFORMANCE.
- Creator
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Stegeman, Robert, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
The need for more bandwidth in communications has stimulated the search for new fiberizable materials with properties superior to fused silica which is the current state-of-the-art. One of the key properties is Raman gain by which a pump beam amplifies a signal beam of longer wavelength. An apparatus capable of directly measuring the spectral dependence and absolute magnitude of the material Raman gain coefficient using nonlinear optics techniques has been built. Using radiation from a 1064...
Show moreThe need for more bandwidth in communications has stimulated the search for new fiberizable materials with properties superior to fused silica which is the current state-of-the-art. One of the key properties is Raman gain by which a pump beam amplifies a signal beam of longer wavelength. An apparatus capable of directly measuring the spectral dependence and absolute magnitude of the material Raman gain coefficient using nonlinear optics techniques has been built. Using radiation from a 1064 nm Nd:YAG laser as the pump and from a tunable Optical Parametric Generator and Amplifier as the signal, the Raman gain spectrum was measured for different families of glass samples with millimeter thickness. A number of glass families were investigated. Tellurites with added oxides of tungsten, niobium, and thallium produced the largest Raman gain coefficients of any oxide family reported to date, typically 30-50 times higher than that of fused silica. On the other hand, phosphate families were found with spectrally broad Raman gain response, 5 times broader than fused silica and flat to b3dB over the full spectral range in some compositions. Although the chalcogenides were found to photodamage easily, coefficients 50 - 80 times that of fused silica were measured. Finally, a numerical study was undertaken to predict the theoretical performance and noise properties of tellurite fibers for communications. Included in the computer modeling were linear loss; the interaction among multiple pumps and signals; forward and/or backward propagating pump beams; forward, backward and double Rayleigh scattering; noise properties of amplifiers; excess noise, etc. This led to a comparison of the optical signal-to-noise characteristics for Raman gain in a tellurite versus a silica fiber.
Show less - Date Issued
- 2006
- Identifier
- CFE0000928, ucf:46739
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000928
- Title
- ALL-SEMICONDUCTOR HIGH POWER MODE-LOCKED LASER SYSTEM.
- Creator
-
Kim, Kyungbum, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
The objective of this dissertation is to generate high power ultrashort optical pulses from an all-semiconductor mode-locked laser system. The limitations of semiconductor optical amplifier in high energy, ultrashort pulse amplification are reviewed. A method to overcome the fundamental limit of small stored energy inside semiconductor optical amplifier called "eXtreme Chirped Pulse Amplification (X-CPA)" is proposed and studied theoretically and experimentally. The key benefits of the...
Show moreThe objective of this dissertation is to generate high power ultrashort optical pulses from an all-semiconductor mode-locked laser system. The limitations of semiconductor optical amplifier in high energy, ultrashort pulse amplification are reviewed. A method to overcome the fundamental limit of small stored energy inside semiconductor optical amplifier called "eXtreme Chirped Pulse Amplification (X-CPA)" is proposed and studied theoretically and experimentally. The key benefits of the concept of X-CPA are addressed. Based on theoretical and experimental study, an all-semiconductor mode-locked X-CPA system consisting of a mode-locked master oscillator, an optical pulse pre-stretcher, a semiconductor optical amplifier (SOA) pulse picker, an extreme pulse stretcher/compressor, cascaded optical amplifiers, and a bulk grating compressor is successfully demonstrated and generates >kW record peak power. A potential candidate for generating high average power from an X-CPA system, novel grating coupled surface emitting semiconductor laser (GCSEL) devices, are studied experimentally. The first demonstration of mode-locking with GCSELs and associated amplification characteristics of grating coupled surface emitting SOAs will be presented. In an effort to go beyond the record setting results of the X-CPA system, a passive optical cavity amplification technique in conjunction with the X-CPA system is constructed, and studied experimentally and theoretically.
Show less - Date Issued
- 2006
- Identifier
- CFE0001069, ucf:46767
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001069
- Title
- LOW NOISE, HIGH REPETITION RATE SEMICONDUCTOR-BASED MODE-LOCKED LASERS FOR SIGNAL PROCESSING AND COHERENT COMMUNICATIONS.
- Creator
-
Quinlan, Franklyn, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
This dissertation details work on high repetition rate semiconductor mode-locked lasers. The qualities of stable pulse trains and stable optical frequency content are the focus of the work performed. First, applications of such lasers are reviewed with particular attention to applications only realizable with laser performance such as presented in this dissertation. Sources of timing jitter are also reviewed, as are techniques by which the timing jitter of a 10 GHz optical pulse train may be...
Show moreThis dissertation details work on high repetition rate semiconductor mode-locked lasers. The qualities of stable pulse trains and stable optical frequency content are the focus of the work performed. First, applications of such lasers are reviewed with particular attention to applications only realizable with laser performance such as presented in this dissertation. Sources of timing jitter are also reviewed, as are techniques by which the timing jitter of a 10 GHz optical pulse train may be measured. Experimental results begin with an exploration of the consequences on the timing and amplitude jitter of the phase noise of an RF source used for mode-locking. These results lead to an ultralow timing jitter source, with 30 fs of timing jitter (1 Hz to 5 GHz, extrapolated). The focus of the work then shifts to generating a stabilized optical frequency comb. The first technique to generating the frequency comb is through optical injection. It is shown that not only can injection locking stabilize a mode-locked laser to the injection seed, but linewidth narrowing, timing jitter reduction and suppression of superfluous optical supermodes of a harmonically mode-locked laser also result. A scheme by which optical injection locking can be maintained long term is also proposed. Results on using an intracavity etalon for supermode suppression and optical frequency stabilization then follow. An etalon-based actively mode-locked laser is shown to have a timing jitter of only 20 fs (1Hz-5 GHz, extrapolated), optical linewidths below 10 kHz and optical frequency instabilities less than 400 kHz. By adding dispersion compensating fiber, the optical spectrum was broadened to 2 THz and 800 fs duration pulses were obtained. By using the etalon-based actively mode-locked laser as a basis, a completely self-contained frequency stabilized coupled optoelectronic oscillator was built and characterized. By simultaneously stabilizing the optical frequencies and the pulse repetition rate to the etalon, a 10 GHz comb source centered at 1550 nm was realized. This system maintains the high quality performance of the actively mode-locked laser while significantly reducing the size weight and power consumption of the system. This system also has the potential for outperforming the actively mode-locked laser by increasing the finesse and stability of the intracavity etalon. The final chapter of this dissertation outlines the future work on the etalon-based coupled optoelectronic oscillator, including the incorporation of a higher finesse, more stable etalon and active phase noise suppression of the RF signal. Two appendices give details on phase noise measurements that incorporate carrier suppression and the noise model for the coupled optoelectronic oscillator.
Show less - Date Issued
- 2008
- Identifier
- CFE0002252, ucf:47878
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002252
- Title
- LOW NOISE, NARROW OPTICAL LINEWIDTH SEMICONDUCTOR-BASED OPTICAL COMB SOURCE AND LOW NOISE RF SIGNAL GENERATION.
- Creator
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Ozdur, Ibrahim, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
Recently optical frequency combs and low noise RF tones are drawing increased attention due to applications in spectroscopy, metrology, arbitrary waveform generation, optical signal processing etc. This thesis focuses on the generation of low noise RF tones and stabilized optical frequency combs. The optical frequency combs are generated by a semiconductor based external cavity mode-locked laser with a high finesse intracavity etalon. In order to get the lowest noise and broadest bandwidth...
Show moreRecently optical frequency combs and low noise RF tones are drawing increased attention due to applications in spectroscopy, metrology, arbitrary waveform generation, optical signal processing etc. This thesis focuses on the generation of low noise RF tones and stabilized optical frequency combs. The optical frequency combs are generated by a semiconductor based external cavity mode-locked laser with a high finesse intracavity etalon. In order to get the lowest noise and broadest bandwidth from the mode-locked laser, it is critical to know the free spectral range (FSR) of the etalon precisely. First the etalon FSR is measured by using the modified Pound-Drever-Hall (PDH) based method and obtained a resolution of 1 part in 106, which is 2 order of magnitude better than the standard PDH based method. After optimizing the cavity length, RF driving frequency and PDH cavity locking point, the mode-locked laser had an integrated timing jitter of 3 fs (1 Hz- 100 MHz) which is, to the best of our knowledge, the lowest jitter ever reported from a semiconductor based multigigahertz comb source. The mode-locked laser produces ~ 100 comb lines with 10 GHz spacing, a linewidth of ~500 Hz and 75 dB optical signal-to-noise ratio. The same system can also be driven as a regeneratively mode-locked laser with greatly improved noise performance. Another way of generating a low noise RF tone is using an opto-electronic oscillator which uses an optical cavity as a high Q element. Due to the harmonic nature of OEOs, a mode selection element is necessary. Standard OEOs use an RF filter having drawbacks such as broad pass band, high loss, and high thermal noise. In our work, a novel optoelectronic scheme which uses an optical filter (Fabry-Perot etalon) as the mode filter instead of an RF filter is demonstrated. This method has the advantage of having ultra-narrow filtering bandwidths ( ~ 10 kHz for a 10 GHz FSR and 106 finesse) and an extremely low noise RF signal. Experimental demonstration of the proposed method resulted in a 5-10 dB decrease of the OEO noise compared to the conventional OEO setup. Also, by modifying the etalon-based OEO, and using single side band modulation, an optically tunable optoelectronic oscillator is achieved with 10-20 dB lower noise than dual side band modulation. Noise properties of the OEO as a function of optical frequency detuning is also analyzed theoretically and the results are in agreement with experimental results.
Show less - Date Issued
- 2011
- Identifier
- CFE0003573, ucf:48917
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003573
- Title
- QUANTUM DOT BASED MODE-LOCKED SEMICONDUCTOR LASERS AND APPLICATIONS.
- Creator
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Kim, Jimyung, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
In this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-PÃÂÃÂÃÂérot lasers and mode-locked lasers are investigated. The mode-locked lasers investigated include monolithic and curved two-section devices, and colliding pulse mode-locked diode lasers. Ridge waveguide semiconductor lasers have been designed and fabricated by wet etching processes. Electroluminescence of the quantum dot...
Show moreIn this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-PÃÂÃÂÃÂérot lasers and mode-locked lasers are investigated. The mode-locked lasers investigated include monolithic and curved two-section devices, and colliding pulse mode-locked diode lasers. Ridge waveguide semiconductor lasers have been designed and fabricated by wet etching processes. Electroluminescence of the quantum dot lasers is studied. Cavity length dependent lasing via ground state and/or excited state transitions is observed from quantum dot lasers and the optical gain from both transitions is measured. Stable optical pulse trains via ground and excited state transitions are generated using a grating coupled external cavity with a curved two-section device. Large differences in the applied reverse bias voltage on the saturable absorber are observed for stable mode-locking from the excited and ground state mode-locking regimes. The optical pulses from quantum dot mode-locked lasers are investigated in terms of chirp sign and linear chirp magnitude. Upchirped pulses with large linear chirp magnitude are observed from both ground and excited states. Externally compressed pulse widths from the ground and excited states are 1.2 ps and 970 fs, respectively. Ground state optical pulses from monolithic mode-locked lasers e.g., two-section devices and colliding pulse mode-locked lasers, are also studied. Transformed limited optical pulses (~4.5 ps) are generated from a colliding pulse mode-locked semiconductor laser. The above threshold linewidth enhancement factor of quantum dot Fabry-PÃÂÃÂÃÂérot lasers is measured using the continuous wave injection locking method. A strong spectral dependence of the linewidth enhancement factor is observed around the gain peak. The measured linewidth enhancement factor is highest at the gain peak, but becomes lower 10 nm away from the gain peak. The lowest linewidth enhancement factor is observed on the anti-Stokes side. The spectral dependence of the pulse duration from quantum dot based mode-locked lasers is also observed. Shorter pulses and reduced linear chirp are observed on the anti-Stokes side and externally compressed 660 fs pulses are achieved in this spectral regime. A novel clock recovery technique using passively mode-locked quantum dot lasers is investigated. The clock signal (~4 GHz) is recovered by injecting an interband optical pulse train to the saturable absorber section. The excited state clock signal is recovered through the ground state transition and vice-versa. Asymmetry in the locking bandwidth is observed. The measured locking bandwidth is 10 times wider when the excited state clock signal is recovered from the ground state injection, as compared to recovering a ground state clock signal from excited state injection.
Show less - Date Issued
- 2010
- Identifier
- CFE0003295, ucf:48493
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003295
- Title
- LOW NOISE AND LOW REPETITION RATE SEMICONDUCTOR-BASED MODE-LOCKED LASERS.
- Creator
-
Mnaridis, Dimitrios, Delfyett, Peter, University of Central Florida
- Abstract / Description
-
The topic of this dissertation is the development of low repetition rate and low noise semiconductor-based laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the...
Show moreThe topic of this dissertation is the development of low repetition rate and low noise semiconductor-based laser sources with a focus on linearly chirped pulse laser sources. In the past decade chirped optical pulses have found a plethora of applications such as photonic analog-to-digital conversion, optical coherence tomography, laser ranging, etc. This dissertation analyzes the aforementioned applications of linearly chirped pulses and their technical requirements, as well as the performance of previously demonstrated chirped pulse laser sources. Moreover, the focus is shifted to a specific application of the linearly chirped pulses, time-stretched photonic analog-to-digital conversion (TS ADC). The challenges of surpassing the speeds of current electronic converters are discussed, while the need for low noise linearly chirped pulse lasers becomes apparent for the realization of TS ADC. The experimental research addresses the topic of low noise chirped pulse generation in three distinct ways. First, a chirped pulse (Theta) laser with an intra-cavity Fabry-Perot etalon and a long-term referencing mechanism is developed that results in the reduction of the pulse-to-pulse energy noise. Noise suppression of >15 times is demonstrated. Moreover, an optical frequency comb with spacing equal to the repetition rate (H100 MHz) is generated using the etalon, resulting in the first reported demonstration of a system operating in the sub-GHz regime based on semiconductor gain. The path for the development of the Theta laser was laid by the precise characterization of the etalon used in this laser cavity design. A narrow linewidth laser is used in conjunction with an acousto-optic modulator externally swept for measuring the etalon's free spectral range with a sub-Hz precision, or 10 parts per billion. Furthermore, the measurement of the etalon long-term drift and birefringence lead to the development of a modified intra-cavity Hansch-Couillaud locking mechanism for the Theta laser. Moreover, an external feed-forward system was demonstrated that aimed at increasing the temporal/spectral uniformity of the optical pulses. A complete characterization of the system is demonstrated. On a different series of experiments, the pulses emitted by an ultra-low noise but high repetition rate mode-locked laser were demultiplexed resulting in a low repetition rate pulse train. Experimental investigation of the noise properties of the laser proved that they are preserved during the demultiplexing process. The noise of the electrical gate used in this experiment is also investigated which led into the development of a more profound understanding of the electrical noise of periodical pulses and a mechanism of measuring their noise. The appendices in this dissertation provide additional material used for the realization of the main research focus of the dissertation. Measurements of the group delay of the etalon used in the Theta laser are presented in order to demonstrate the limiting factors for the development of this cavity design. The description of a balancing routine is presented, that was used for expanding the dynamic range of intra-cavity active variable delay. At last, the appendix presents the calculations regarding the contribution of various parameters in the limitations of analog-to-digital conversion.
Show less - Date Issued
- 2011
- Identifier
- CFE0003874, ucf:48741
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003874
- Title
- Thin-film Lithium Niobate Photonics for Electro-optics, Nonlinear Optics, and Quantum Optics on Silicon.
- Creator
-
Rao, Ashutosh, Fathpour, Sasan, Delfyett, Peter, Li, Guifang, Thomas, Jayan, University of Central Florida
- Abstract / Description
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Ion-sliced thin-film lithium niobate (LN) compact waveguide technology has facilitated the resurgence of integrated photonics based on lithium niobate. These thin-film LN waveguides offer over an order of magnitude improvement in optical confinement, and about two orders of magnitude reduction in waveguide bending radius, compared to conventional LN waveguides. Harnessing the improved confinement, a variety of miniaturized and efficient photonic devices are demonstrated in this work. First,...
Show moreIon-sliced thin-film lithium niobate (LN) compact waveguide technology has facilitated the resurgence of integrated photonics based on lithium niobate. These thin-film LN waveguides offer over an order of magnitude improvement in optical confinement, and about two orders of magnitude reduction in waveguide bending radius, compared to conventional LN waveguides. Harnessing the improved confinement, a variety of miniaturized and efficient photonic devices are demonstrated in this work. First, two types of compact electrooptic modulators are presented (-) microring modulators, and Mach-Zehnder modulators. Next, two distinct approaches to nonlinear optical frequency converters are implemented (-) periodically poled lithium niobate, and mode shape modulation (grating assisted quasi-phase matching). Following this, stochastic variations are added to the mode shape modulation approach to demonstrate random quasi-phase matching. Afterward, broadband photon-pair generation is demonstrated in the miniaturized periodically poled lithium niobate, and spectral correlations of the biphoton spectrum are reported. Finally, extensions of the aforementioned results suitable for future work are discussed.
Show less - Date Issued
- 2018
- Identifier
- CFE0007085, ucf:52013
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007085
- Title
- Generation and Characterization of Isolated Attosecond Pulse in the Soft X-ray Regime.
- Creator
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Li, Jie, Chang, Zenghu, Delfyett, Peter, Vanstryland, Eric, Chen, Bo, University of Central Florida
- Abstract / Description
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The observation of any atomic and molecular dynamics requires a probe that has a timescale comparable to the dynamics itself. Ever since the invention of laser, the temporal duration of the laser pulse has been incrementally reduced from several nanoseconds to just attoseconds. Picosecond and femtosecond laser pulses have been widely used to study molecular rotation and vibration. In 2001, the first single isolated attosecond pulse (1 attosecond = 10^-18 seconds.) was demonstrated. Since this...
Show moreThe observation of any atomic and molecular dynamics requires a probe that has a timescale comparable to the dynamics itself. Ever since the invention of laser, the temporal duration of the laser pulse has been incrementally reduced from several nanoseconds to just attoseconds. Picosecond and femtosecond laser pulses have been widely used to study molecular rotation and vibration. In 2001, the first single isolated attosecond pulse (1 attosecond = 10^-18 seconds.) was demonstrated. Since this breakthrough, (")attoscience(") has become a hot topic in ultrafast physics. Attosecond pulses typically have span between EUV to X-ray photon energies and sub-femtosecond pulse duration. It becomes an ideal tool for experimentalists to study ultrafast electron dynamics in atoms, molecules and condensed matter. The conventional scheme for generating attosecond pulses is focusing an intense femtosecond laser pulse into inert gases. The bound electrons are ionized into continuum through tunneling ionization under the strong electrical field. After ionization, the free electron will be accelerated by the laser field away from the parent ion and then recombined with its parent ion and releases its kinetic energy as a photon burst that lasts for a few hundred attoseconds. According to the classical (")three-step model("), high order harmonic will have a higher cutoff photon energy when driven by a longer wavelength laser field. Compared to Ti:sapphire lasers center at a wavelength of 800 nm, an optical parametric amplifier could offer a broad bandwidth at infrared range, which could support few cycle pulses for driving high harmonic generation in the X-ray spectrum range. In this work, an optical parametric chirped-pulse amplification system was developed to deliver CEP-stable 3-mJ, 12-fs pulses centered at 1.7 micron. We implement a chirped-pump technique to phase match the board parametric amplification bandwidth with high conversion efficiency. Using such a laser source, isolated attosecond pulses with photon exceeding 300 eV are achieved by applying the polarization gating technique at 1.7 micron. The intrinsic positive chirp of the attosecond pulses is measured by the attosecond streak camera and retrieved with our PROOF technique. Sn metal filters with negative dispersion were chosen to compensate the intrinsic attochirp. As a result, isolated 53-attosecond soft x-ray pulses are achieved. Such water window attosecond source will be a powerful tool for studying charge distribution/migration in bio-molecules and will bring opportunities to study high field physics or attochemistry.
Show less - Date Issued
- 2018
- Identifier
- CFE0007040, ucf:52007
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007040
- Title
- Room Temperature Operation of Quantum Cascade Lasers Monolithically Integrated Onto a Lattice-Mismatched Substrate.
- Creator
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Go, Rowel, Lyakh, Arkadiy, Delfyett, Peter, Likamwa, Patrick, Wu, Shintson, University of Central Florida
- Abstract / Description
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The experimental results of a 40-stage indium phosphide (InP) based quantum cascade laser (QCL) grown on a lattice-mismatched gallium arsenide (GaAs) substrate with metamorphic buffer (M-buffer) will be discussed. The QCL's strain-balanced active region was composed of Al0.78In0.22As/In0.73Ga0.27As and an 8 (&)#181;m-thick all-InP waveguide. Since the M-buffer was insulating, the wafer was processed into ridge-waveguide chips with lateral current injection scheme. Laser chips with high...
Show moreThe experimental results of a 40-stage indium phosphide (InP) based quantum cascade laser (QCL) grown on a lattice-mismatched gallium arsenide (GaAs) substrate with metamorphic buffer (M-buffer) will be discussed. The QCL's strain-balanced active region was composed of Al0.78In0.22As/In0.73Ga0.27As and an 8 (&)#181;m-thick all-InP waveguide. Since the M-buffer was insulating, the wafer was processed into ridge-waveguide chips with lateral current injection scheme. Laser chips with high reflection (HR) coating delivered total peak power in excess of 200 mW at cryogenic temperature (78 K), and lasing was observed up to 230 K. Partial HR coating was then utilized on the front facet to extend lasing range up to 303 K. After 200 minutes of preliminary reliability testing at maximum power, no sign of performance degradation was observed. Initial results of InP-based QCL on germanium-coated silicon substrate with M-buffer will also be covered in this work.
Show less - Date Issued
- 2018
- Identifier
- CFE0007568, ucf:52564
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007568
- 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
- Intracavity Laser Absorption Spectroscopy using Quantum Cascade Laser and Fabry-Perot Interferometer.
- Creator
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Medhi, Gautam, Peale, Robert, Ishigami, Marsahir, Chernyak, Leonid, Delfyett, Peter, University of Central Florida
- Abstract / Description
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Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing of low vapor pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69.9 ?m) and IR wavelengths (9.38 and 8.1 ?m) with an open external cavity. The sensitivity of such a system is potentially very high due to extraordinarily long effective optical paths that can be achieved in an active cavity. Sensitivity estimation by numerical...
Show moreIntracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing of low vapor pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69.9 ?m) and IR wavelengths (9.38 and 8.1 ?m) with an open external cavity. The sensitivity of such a system is potentially very high due to extraordinarily long effective optical paths that can be achieved in an active cavity. Sensitivity estimation by numerical solution of the laser rate equations for the THz QCL ICLAS system is determined. Experimental development of the external cavity QCL is demonstrated for the two IR wavelengths, as supported by appearance of fine mode structure in the laser spectrum. The 8.1 ?m wavelength exhibits a dramatic change in the output spectrum caused by the weak intracavity absorption of acetone. Numerical solution of the laser rate equations yields a sensitivity estimation of acetone partial pressure of 165 mTorr corresponding to ~ 200 ppm. The system is also found sensitive to the humidity in the laboratory air with an absorption coefficient of just 3 x 10-7 cm-1 indicating a sensitivity of 111 ppm. Reported also is the design of a compact integrated data acquisition and control system. Potential applications include military and commercial sensing for threat compounds such as explosives, chemical gases, biological aerosols, drugs, banned or invasive organisms, bio-medical breath analysis, and terrestrial or planetary atmospheric science.
Show less - Date Issued
- 2011
- Identifier
- CFE0004137, ucf:49040
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004137
- Title
- Injection-locked semiconductor lasers for realization of novel RF photonics components.
- Creator
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Hoghooghi, Nazanin, Delfyett, Peter, Likamwa, Patrick, Li, Guifang, Malocha, Donald, University of Central Florida
- Abstract / Description
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This dissertation details the work has been done on a novel resonant cavity linear interferometric modulator and a direct phase detector with channel filtering capability using injection-locked semiconductor lasers for applications in RF photonics. First, examples of optical systems whose performance can be greatly enhanced by using a linear intensity modulator are presented and existing linearized modulator designs are reviewed. The novel linear interferometric optical intensity modulator...
Show moreThis dissertation details the work has been done on a novel resonant cavity linear interferometric modulator and a direct phase detector with channel filtering capability using injection-locked semiconductor lasers for applications in RF photonics. First, examples of optical systems whose performance can be greatly enhanced by using a linear intensity modulator are presented and existing linearized modulator designs are reviewed. The novel linear interferometric optical intensity modulator based on an injection-locked laser as an arcsine phase modulator is introduced and followed by numerical simulations of the phase and amplitude response of an injection-locked semiconductor laser. The numerical model is then extended to study the effects of the injection ratio, nonlinear cavity response, depth of phase and amplitude modulation on the spur-free dynamic range of a semiconductor resonant cavity linear modulator. Experimental results of the performance of the linear modulator implemented with a multi-mode Fabry-Perot semiconductor laser as the resonant cavity are shown and compared with the theoretical model. The modulator performance using a vertical cavity surface emitting laser as the resonant cavity is investigated as well. Very low V? in the order of 1 mV, multi-gigahertz bandwidth (-10 dB bandwidth of 5 GHz) and a spur-free dynamic range of 120 dB.Hz2/3 were measured directly after the modulator. The performance of the modulator in an analog link is experimentally investigated and the results show no degradation of the modulator linearity after a 1 km of SMF.The focus of the work then shifts to applications of an injection-locked semiconductor laser as a direct phase detector and channel filter. This phase detection technique does not require a local oscillator. Experimental results showing the detection and channel filtering capability of an injection-locked semiconductor diode laser in a three channel system are shown. The detected electrical signal has a signal-to-noise ratio better than 60 dB/Hz. In chapter 4, the phase noise added by an injection-locked vertical cavity surface emitting laser is studied using a self-heterodyne technique. The results show the dependency of the added phase noise on the injection ratio and detuning frequency. The final chapter outlines the future works on the linear interferometric intensity modulator including integration of the modulator on a semiconductor chip and the design of the modulator for input pulsed light.
Show less - Date Issued
- 2012
- Identifier
- CFE0004385, ucf:49368
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004385
- 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
- Multi-Purpose device for analyzing and measuring ultra-short pulses.
- Creator
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Mehta, Naman Anilkumar, Schulzgen, Axel, Delfyett, Peter, Amezcua Correa, Rodrigo, University of Central Florida
- Abstract / Description
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Intensity auto correlator is device to measure pulse widths of ultrashort pulses on the order of picosecondsand femtoseconds. I have built an in-house, compact, portable, industry standard intensityauto correlator for measuring ultrashort pulse-widths. My device is suitable for pulse-widthsfrom 500 ps to 50 fs. The impetus for developing this instrument stemmed from our developmentof a multicore-fiber laser for high power laser applications, which also produces very short pulsesthat cannot be...
Show moreIntensity auto correlator is device to measure pulse widths of ultrashort pulses on the order of picosecondsand femtoseconds. I have built an in-house, compact, portable, industry standard intensityauto correlator for measuring ultrashort pulse-widths. My device is suitable for pulse-widthsfrom 500 ps to 50 fs. The impetus for developing this instrument stemmed from our developmentof a multicore-fiber laser for high power laser applications, which also produces very short pulsesthat cannot be measured with an oscilloscope. As techniques for measuring short pulse-widthshave been well studied, what made my journey exciting was the process of taking an idea and realizinga successful, cost-efficient device. In this study, I have analyzed a Q-switched laser and mymeasured pulse-width matched the theoretical value previously calculated. I have also analyzedour mode-locked multicore fiber laser and results were encouraging. The notion to build one intensityautocorrelator was based on our labs future work, which was with modelocked multicore fiberlaser, which at the moment is giving pulses on order of nanoseconds. Dr. Axel Schulzgen gavethe responsibility to build an intensity autocorrelator on my shoulders. As, Intensity autocorrelatorshave been around for long time, he encouraged me to make one in house, compact, portableintensity autocorrelator which measures pulse widths of 50 fs up to 500 ps quite easily.
Show less - Date Issued
- 2016
- Identifier
- CFE0006353, ucf:51508
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006353