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- 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
- Mode-locked Laser Based on Large Core Yb3+-Doped Fiber.
- Creator
-
Jia, Fei, Amezcua Correa, Rodrigo, Schulzgen, Axel, Fathpour, Sasan, University of Central Florida
- Abstract / Description
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The thesis reviews principle of laser cavity and gives a general introduction to mode-locked laser (MLL). By using Yb3+-doped fiber as gain medium, passive MLL cavity is developed in experiment, aiming to obtain femtosecond pulses with high pump power from 25W to 35W. The gain medium fiber with 65(&)#181;m core diameter is cleaved with one flat end and another angled. Pump laser with 976nm wavelength is coupled into Yb3+-doped fiber to excite signal from 1020nm to 1040nm in the core. 9W is...
Show moreThe thesis reviews principle of laser cavity and gives a general introduction to mode-locked laser (MLL). By using Yb3+-doped fiber as gain medium, passive MLL cavity is developed in experiment, aiming to obtain femtosecond pulses with high pump power from 25W to 35W. The gain medium fiber with 65(&)#181;m core diameter is cleaved with one flat end and another angled. Pump laser with 976nm wavelength is coupled into Yb3+-doped fiber to excite signal from 1020nm to 1040nm in the core. 9W is threshold for laser setup. After locking all modes, picosecond pulses are output from laser cavity and coupled into dispersion delay fiber. By compressing pulse width, pulses are in soliton mode and then femtosecond laser pulses are obtained pulses are obtained. To measure ultrafast pulse width effectively, an auto-correlator based on Mach(-)Zehnder interferometer is developed. In the receiver terminal, a photodiode with range 320 nm to 1000 nm is used to detect signal and two photon absorption (TPA) method is applied.
Show less - Date Issued
- 2018
- Identifier
- CFE0007199, ucf:52249
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007199
- 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
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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
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In this dissertation, self-assembled InAs/InGaAs quantum dot Fabry-Pérot 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-Pérot 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-Pérot 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
- Broad Bandwidth Optical Frequency Combs from Low Noise, High Repetition Rate Semiconductor Mode-Locked Lasers.
- Creator
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Klee, Anthony, Delfyett, Peter, Vanstryland, Eric, Schulzgen, Axel, DeSalvo, Richard, University of Central Florida
- Abstract / Description
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Mode-locked lasers have numerous applications in the areas of communications, spectroscopy, and frequency metrology. Harmonically mode-locked semiconductor lasers with external ring cavities offer a unique combination of benefits in that they can produce high repetition rate pulse trains with low timing jitter, achieve narrow axial mode linewidths, have the potential for entire monolithic integration on-chip, feature high wall-plug efficiency due to direct electrical pumping, and can be...
Show moreMode-locked lasers have numerous applications in the areas of communications, spectroscopy, and frequency metrology. Harmonically mode-locked semiconductor lasers with external ring cavities offer a unique combination of benefits in that they can produce high repetition rate pulse trains with low timing jitter, achieve narrow axial mode linewidths, have the potential for entire monolithic integration on-chip, feature high wall-plug efficiency due to direct electrical pumping, and can be engineered to operate in different wavelength bands of interest. However, lasers based on InP/InGaAsP quantum well devices which operate in the important telecom C-band have thus far been relatively limited in bandwidth as compared to competing platforms. Broad bandwidth is critical for increasing information carrying capacity and enabling femtosecond pulse production for coherent continuum generation in offset frequency stabilization. The goal of the work in this dissertation is to maximize the bandwidth of semiconductor lasers, bringing them closer to reaching their full potential as all-purpose sources.Dispersion in the laser cavity is a primary limiter of the achievable bandwidth in the laser architectures covered in this dissertation. In the first part of this dissertation, an accurate self-referenced technique based on multi-heterodyne detection is developed for measuring the spectral phase of a mode-locked laser. This technique is used to characterize the dispersion in several semiconductor laser architectures. In the second part, this knowledge is applied to reduce the dispersion in a laser cavity using a programmable pulse shaper, and thus increase the laser's spectral bandwidth. We demonstrate a 10 GHz frequency comb with bandwidth spanning 5 THz, representing a twofold improvement over the previously achievable bandwidth. Finally, this laser is converted to a stand-alone system by reconfiguring it as a coupled opto-electronic oscillator and a novel stabilization scheme is presented.
Show less - Date Issued
- 2016
- Identifier
- CFE0006129, ucf:51184
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006129
- Title
- External cavity mode-locked semiconductor lasers for the generation of ultra-low noise multi-gigahertz frequency combs and applications in multi-heterodyne detection of arbitrary optical waveforms.
- Creator
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Davila-Rodriguez, Josue, Delfyett, Peter, Likamwa, Patrick, Li, Guifang, Malocha, Donald, University of Central Florida
- Abstract / Description
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The construction and characterization of ultra-low noise semiconductor-based mode-locked lasers as frequency comb sources with multi-gigahertz combline-to-combline spacing is studied in this dissertation. Several different systems were built and characterized. The first of these systems includes a novel mode-locking mechanism based on phase modulation and periodic spectral filtering. This mode-locked laser design uses the same intra-cavity elements for both mode-locking and frequency...
Show moreThe construction and characterization of ultra-low noise semiconductor-based mode-locked lasers as frequency comb sources with multi-gigahertz combline-to-combline spacing is studied in this dissertation. Several different systems were built and characterized. The first of these systems includes a novel mode-locking mechanism based on phase modulation and periodic spectral filtering. This mode-locked laser design uses the same intra-cavity elements for both mode-locking and frequency stabilization to an intra-cavity, 1,000 Finesse, Fabry-P(&)#233;rot Etalon (FPE). On a separate effort, a mode-locked laser based on a Slab-Coupled Optical Waveguide Amplifier (SCOWA) was built. This system generates a pulse-train with residual timing jitter of (<)2 fs and pulses compressible to (<)1 ps. Amplification of these pulse-trains with an external SCOWA lead to 390 mW of average optical power without evident degradation in phase noise and pulses that are compressible to the sub-picosecond regime. Finally, a new laser is built using a 10,000 Finesse Fabry-P(&)#233;rot Etalon held in a vacuum chamber. The fluctuations in the optical frequency of the individual comb-lines over time periods longer than 12 minutes are shown to be significantly reduced to (<)100 kHz in a measurement that is limited by the linewidth of the reference source.The use of these comb sources as local oscillators in multi-heterodyne detection of arbitrary optical waveforms is explored in three different cases. 1) Sampling of mode-locked pulses, 2) sampling of phase modulated continuous wave light and 3) periodically filtered white light. The last experiment achieves spectral interferometry with unprecedented resolution.
Show less - Date Issued
- 2013
- Identifier
- CFE0004669, ucf:49863
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004669
- Title
- ULTRASHORT, HIGH POWER, AND ULTRALOW NOISE MODE-LOCKED OPTICAL PULSE GENERATION USING QUANTUM-DOT SEMICONDUCTOR LASERS.
- Creator
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Choi, Myoung-Taek, Delfyett, Peter, University of Central Florida
- Abstract / Description
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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
- HIGH POWER MODE-LOCKED SEMICONDUCTOR LASERS AND THEIR APPLICATIONS.
- Creator
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Lee, Shinwook, Delfyett, Peter, University of Central Florida
- Abstract / Description
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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
- LOW NOISE, HIGH REPETITION RATE SEMICONDUCTOR-BASED MODE-LOCKED LASERS FOR SIGNAL PROCESSING AND COHERENT COMMUNICATIONS.
- Creator
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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 AND LOW REPETITION RATE SEMICONDUCTOR-BASED MODE-LOCKED LASERS.
- Creator
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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
- 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
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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
- Title
- Injection-Locked Vertical Cavity Surface Emitting Lasers (VCSELs) for Optical Arbitrary Waveform Generation.
- Creator
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Bhooplapur, Sharad, Delfyett, Peter, Li, Guifang, Christodoulides, Demetrios, Malocha, Donald, University of Central Florida
- Abstract / Description
-
Complex optical pulse shapes are typically generated from ultrashort laser pulses by manipulating the optical spectrum of the input pulses. This generates complex but periodic time-domain waveforms. Optical Arbitrary Waveform Generation (OAWG) builds on the techniques of ultrashort pulse?shaping, with the goal of making non?periodic, truly arbitrary optical waveforms. Some applications of OAWG are coherently controlling chemical reactions on a femtosecond time scale, improving the performance...
Show moreComplex optical pulse shapes are typically generated from ultrashort laser pulses by manipulating the optical spectrum of the input pulses. This generates complex but periodic time-domain waveforms. Optical Arbitrary Waveform Generation (OAWG) builds on the techniques of ultrashort pulse?shaping, with the goal of making non?periodic, truly arbitrary optical waveforms. Some applications of OAWG are coherently controlling chemical reactions on a femtosecond time scale, improving the performance of LADAR systems, high?capacity optical telecommunications and ultra wideband signals processing.In this work, an array of Vertical Cavity Surface Emitting Lasers (VCSELs) are used as modulators, by injection-locking each VCSEL to an individual combline from an optical frequency comb source. Injection-locking ensures that the VCSELs' emission is phase coherent with the input combline, and modulating its current modulates mainly the output optical phase. The multi-GHz modulation bandwidth of VCSELs updates the output optical pulse shape on a pulse-to-pulse time scale, which is an important step towards true OAWG. In comparison, it is about a million times faster than the liquid-crystal modulator arrays typically used for pulse shaping! Novel components and subsystems of Optical Arbitrary Waveform Generation (OAWG) are developed and demonstrated in this work. They include:1.Modulators An array of VCSELs is packaged and characterized for use as a modulator for rapid?update pulse?shaping at GHz rates. The amplitude and phase modulation characteristics of an injection?locked VCSEL are simultaneously measured at GHz modulation rates.2.Optical Frequency Comb SourcesAn actively mode?locked semiconductor laser was assembled, with a 12.5 GHz repetition rate, ~ 200 individually resolvable comblines directly out of the laser, and high frequency stability. In addition, optical frequency comb sources are generated by modulation of a single frequency laser.3.High-resolution optical spectral demultiplexersThe demultiplexers are implemented using bulk optics, and are used to spatially resolve individual optical comblines onto the modulator array. 4.Optical waveform measurement techniques Several techniques are used to measure generated waveforms, especially for spectral phase measurements, including multi-heterodyne phase retrieval. In addition, an architecture for discriminating between ultrashort encoded optical pulses with record high sensitivity is demonstrated.
Show less - Date Issued
- 2014
- Identifier
- CFE0005466, ucf:50402
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005466
- Title
- True linearized intensity modulation for photonic analog to digital conversion using an injection-locked mode-locked laser.
- Creator
-
Sarailou, Edris, Delfyett, Peter, Likamwa, Patrick, Fathpour, Sasan, Malocha, Donald, University of Central Florida
- Abstract / Description
-
A true linearized interferometric intensity modulator for pulsed light has been proposed and experimentally presented in this thesis. This has been achieved by introducing a mode-locked laser into one of the arms of a Mach-Zehnder interferometer and injection-locking it to the input light (which is pulsed and periodic). By modulating the injection-locked laser, and combining its output light with the light from the other arm of interferometer in quadrature, one can achieve true linearized...
Show moreA true linearized interferometric intensity modulator for pulsed light has been proposed and experimentally presented in this thesis. This has been achieved by introducing a mode-locked laser into one of the arms of a Mach-Zehnder interferometer and injection-locking it to the input light (which is pulsed and periodic). By modulating the injection-locked laser, and combining its output light with the light from the other arm of interferometer in quadrature, one can achieve true linearized intensity modulator. This linearity comes from the arcsine phase response of the injection-locked mode-locked laser (as suggested by steady-state solution of Adler's equation) when it is being modulated. Mode-locked lasers are fabricated using a novel AlGaInAs-InP material system. By using the BCB for planarization and minimizing the metal pad size and directly modulating the laser, we have achieved very effective fundamental hybrid mode-locking at the repetition rate of ~ 23 GHz. This laser also provided the short pulses of 860 fs and 280 fs timing jitter integrated from 1 Hz- 100 MHz.The linearized intensity modulator has been built by using two identical two-section mode-locked lasers with the same length, one as the slave laser in one of the arms of the Mach-Zehnder interferometer injection-locked to the other one as the master which is the input light to the modulator. A low V? of 8.5 mV is achieved from this modulator. Also the current of the gain section or the voltage of the saturable absorber section of the slave laser has been used to apply the modulation signal. A spur free dynamic range of 70 dB.Hz2/3 is achieved when modulating the modulator through the saturable absorber. Modulating the saturable absorber provides a reduced third-order intermodulation tone with respect to modulating the gain. This is simply because of the unwanted amplitude modulation created when modulating the gain section current.Finally an improved design is proposed and demonstrated to improve the modulator performance. This is achieved by introducing a third section to the laser. Using the impurity free vacancy disordering technique the photoluminescence peak of this section is blue-shifted selectively and therefore there would not be any absorption in that passive section. By applying the modulation signal to this passive section rather than applying it to the gain section or saturable absorber section, the amplitude and phase modulation could be decoupled. The experimental results have presented here and an almost six-fold reduction in V? and 5 dB improvement in spur free dynamic range have been achieved. The proposed and demonstrated configuration as an analog optical link has the potential to increase the performance and resolution of photonic analog-to-digital converters.
Show less - Date Issued
- 2015
- Identifier
- CFE0005707, ucf:50118
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005707
- Title
- HIGH-SPEED MODELOCKED SEMICONDUCTOR LASERS AND APPLICATIONS IN COHERENT PHOTONIC SYSTEMS.
- Creator
-
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
- DISPERSION-MANAGED BREATHING-MODE SEMICONDUCTOR MODE-LOCKED RING LASER: EXPERIMENTAL STUDY, NUMERICAL SIMULATIONS AND APPLICATIONS.
- Creator
-
Resan, Bojan, Delfyett, Peter J., University of Central Florida
- Abstract / Description
-
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
- A laser radar employing linearly chirped pulses from a mode-locked laser for long range, unambiguous, sub-millimeter resolution ranging and velocimetry.
- Creator
-
Piracha, Mohammad Umar, ,, University of Central Florida
- Abstract / Description
-
Light detection and ranging (lidar) is used for various applications such as remote sensing, altimetry and imaging. In this talk, a linearly chirped pulse source is introduced that generates wavelength-swept pulses exhibiting ~6 nm optical bandwidth with (>) 20 km coherence length. The chirped pulses are used in an interferometric lidar setup to perform distance measurements with sub-millimeter resolution (using pulses that are a few meters long), at target distances (>) 10 km, with at least...
Show moreLight detection and ranging (lidar) is used for various applications such as remote sensing, altimetry and imaging. In this talk, a linearly chirped pulse source is introduced that generates wavelength-swept pulses exhibiting ~6 nm optical bandwidth with (>) 20 km coherence length. The chirped pulses are used in an interferometric lidar setup to perform distance measurements with sub-millimeter resolution (using pulses that are a few meters long), at target distances (>) 10 km, with at least 25 dB signal-to-noise ratio at the receiver. A pulse repetition rate of 20 MHz provides fast update rates, while chirped pulse amplification allows easy amplification of optical signals to high power levels that are required for long range operation. A pulse tagging scheme based on phase modulation is used to demonstrate unambiguous, long range measurements. In addition to this, simultaneous measurement of target range and Doppler velocity is performed using a target moving at a speed of over 330 km/h (205 mph) inside the laboratory. In addition to this, spectral phase modulation of the chirped pulses is demonstrated to compensate for the undesirable ripple in the group delay of the chirped pulses. Moreover, spectral amplitude modulation is used to generate pulses with Gaussian temporal intensity profiles and a two-fold increase in the lidar range resolution (284 um) is observed.
Show less - Date Issued
- 2012
- Identifier
- CFE0004423, ucf:49409
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004423
- Title
- Injection Locking of Semiconductor Mode-Locked Lasers for Long-Term Stability of Widely Tunable Frequency Combs.
- Creator
-
Williams, Charles, Delfyett, Peter, Hagan, David, Likamwa, Patrick, Vanstryland, Eric, DeSalvo, Richard, University of Central Florida
- Abstract / Description
-
Harmonically mode-locked semiconductor lasers with external ring cavities offer high repetition rate pulse trains while maintaining low optical linewidth via long cavity storage times. Single frequency injection locking generates widely-spaced and tunable frequency combs from these harmonically mode-locked lasers, while stabilizing the optical frequencies. The output is stabilized long-term with the help of a feedback loop utilizing either a novel technique based on Pound-Drever-Hall...
Show moreHarmonically mode-locked semiconductor lasers with external ring cavities offer high repetition rate pulse trains while maintaining low optical linewidth via long cavity storage times. Single frequency injection locking generates widely-spaced and tunable frequency combs from these harmonically mode-locked lasers, while stabilizing the optical frequencies. The output is stabilized long-term with the help of a feedback loop utilizing either a novel technique based on Pound-Drever-Hall stabilization or by polarization spectroscopy. Error signals of both techniques are simulated and compared to experimentally obtained signals. Frequency combs spaced by 2.5 GHz and ~10 GHz are generated, with demonstrated optical sidemode suppression of unwanted modes of 36 dB, as well as RF supermode noise suppression of 14 dB for longer than 1 hour. In addition to the injection locking of actively harmonically mode-locked lasers, the injection locking technique for regeneratively mode-locked lasers, or Coupled Opto-Electronic Oscillators (COEOs), is also demonstrated and characterized extensively.
Show less - Date Issued
- 2013
- Identifier
- CFE0004774, ucf:49805
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004774
- Title
- On-Chip Optical Stabilization of High-Speed Mode-locked Quantum Dot Lasers for Next Generation Optical Networks.
- Creator
-
Ardey, Abhijeet, Delfyett, Peter, Chow, Lee, Peale, Robert, Likamwa, Patrick, University of Central Florida
- Abstract / Description
-
Monolithic passively mode-locked colliding pulse semiconductor lasers generating pico- to sub-picosecond terahertz optical pulse trains are promising sources for future applications in ultra-high speed data transmission systems and optical measurements. However, in the absence of external synchronization, these passively mode-locked lasers suffer from large amplitude and timing jitter instabilities resulting in broad comb linewidths, which precludes many applications in the field of coherent...
Show moreMonolithic passively mode-locked colliding pulse semiconductor lasers generating pico- to sub-picosecond terahertz optical pulse trains are promising sources for future applications in ultra-high speed data transmission systems and optical measurements. However, in the absence of external synchronization, these passively mode-locked lasers suffer from large amplitude and timing jitter instabilities resulting in broad comb linewidths, which precludes many applications in the field of coherent communications and signal processing where a much narrower frequency line set is needed. In this dissertation, a novel quantum dot based coupled cavity laser is presented, where for the first time, four-wave mixing (FWM) in the monolithically integrated saturable absorber is used to injection lock a monolithic colliding pulse mode-locked (CPM) laser with a mode-locked high-Q ring laser. Starting with a passively mode-locked master ring laser, a stable 30 GHz optical pulse train is generated with more than 10 dB reduction in the RF noise level at 20 MHz offset and close to 3-times reduction in the average optical linewidth of the injection locked CPM slave laser. The FWM process is subsequently verified experimentally and conclusively shown to be the primary mechanism responsible for the observed injection locking. Other linear scattering effects are found to be negligible, as predicted in the orthogonal waveguide configuration. The novel injection locking technique is further exploited by employing optical hybrid mode-locking and increasing the Q of the master ring cavity, to realize an improved stabilization architecture. Dramatic reduction is shown with more than 14-times reduction in the photodetected beat linewidth and almost 5-times reduction in the optical linewidth of the injection locked slave laser with generation of close to transform limited pulses at ~ 30 GHz. These results demonstrate the effectiveness of the novel injection locking technique for an all-on-chip stability transfer and provides a new way of stabilizing monolithic optical pulse sources for applications in future high speed optical networks.
Show less - Date Issued
- 2014
- Identifier
- CFE0005299, ucf:50518
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005299
- 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
