Fiber Optic Devices Pumped with Semiconductor Disk Lasers

The aim of this thesis is to investigate the advantages of pumping fiber optic oscillators utilizing a special type of lasers – semiconductor disk lasers. Relatively novel semiconductor disk laser technology offers low relative intensity noise levels combined with scalable output power, stable operation and nearly diffraction-limited beam quality valuable for an efficient fiber coupling (70- 90%). This pumping technique was applied for optical pumping of fiber lasers. Low-noise fiber Raman amplifier in co-propagation configuration for pump and signal was developed in the 1.3 μm spectral range. A hybrid Raman-bismuth-doped fiber amplifier scheme for an efficient pump light conversion was proposed and demonstrated. Semiconductor disk lasers operating at 1.29 μm and 1.48 μm were used as the pump sources for picosecond Raman fiber lasers at 1.38 and 1.6 μm. The 1.38 μm passively modelocked Raman fiber laser produced 1.97 ps pulses with a ring cavity configuration. The 1.6 μm linear cavity fiber laser with the integrated SESAM produced 2.7 ps output. A picosecond semiconductor disk laser followed by the ytterbium-erbium fiber amplifier offered supercontinuum generation spanning from 1.35 μm to 2 μm with an average power of 3.5 W. By utilizing a 1.15 μm semiconductor disk laser, a pulsed Ho3+-doped fiber lasers for a 2 μm spectral band were demonstrated. 118 nJ pulses at the repetition rate of 170 kHz and central wavelength of 2097 nm were produced by a holmium fiber laser Q-switched by a carbon nanotube saturable absorber. Sub-picosecond holmium-doped fiber laser modelocked with a broadband carbon nanotube saturable absorber and a SESAM were developed. Using the former saturable absorber, ultrashort pulse operation with the duration of ~ 890 fs in the 2030-2100 nm wavelength range was obtained. The results in the presented dissertation demonstrate the potential of the semiconductor disk laser technology for pumping fiber amplifiers and ultrafast lasers

Hybrid WDM-TDM Optical Communication and Data Link

A hybrid WDM-TDM optical link employing a hybrid modelocked multi-wavelength semiconductor which provides approximately 4 to approximately 20 wavelength channels that makes possible modulated multiplexed data which when demultiplexed by ultra fast optical demultiplexing provides rates suitable for conventional electronic photo receivers. The link uses single-stripe GaAs/AlGaAs semiconductor optical amplifiers which simultaneously generate from approximately four to more than approximately twenty tunable WDM channels. Diode laser can also include InP, InGaAlP, InGaAsP, InGaP, InGaAs. A four channel version transmits approximately 12 picosecond pulses at approximately 2.5 GHz for an aggregate pulse rate of 100 GHz. When generating approximately 20 wavelength channels, each transmitting approximately 12 picosecond pulses at a rate of approximately 600 MHz, there is provided optical data and transmission systems operating at rates in excess of 800 Gbits/s

Multiwavelength Modelocked Semiconductor Diode Laser

Single-stripe GaAs/AlGaAs semiconductor optical amplifiers which simultaneously generates from four to more than twenty tunable WDM channels. A four channel version transmits approximately 12 picosecond pulses at approximately 2.5 GHz for an aggregate pulse rate of 100 GHz. Wavelength tuning over 18 nm has been demonstrated with channel spacing ranging from approximately 0.8 nm to approximately 2 nm. A second version uses approximately 20 wavelength channels, each transmitting approximately 12 picosecond pulses at a rate of approximately 600 MHz. A spectral correlation across the multiwavelength spectrum which can be for utilizing single stripe laser diodes as multiwavelength sources in WDM-TDM networks. A third version of multiple wavelength generation uses a fiber-array and grating. And a fourth version of wavelength generation uses a Fabry-Perot Spectral filter. Also solid state laser sources and optical fiber laser sources can be used

Multiwavelength Modelocked Semiconductor Diode Laser

Single-stripe GaAs/AlGaAs semiconductor optical amplifiers which simultaneously generates from four to more than twenty tunable WDM channels. A four channel version trsnsmits approximately 12 picosecond pulses at approximately 2.5 GHz for an aggregate pulse rate of 100 GHz. Wavelength tuning over 18 nm has been demonstrated with channel spacing ranging from approximately 0.8 nm to approximately 2 nm. A second version uses approximately 20 wavelength channels, each transmitting approximately 12 picosecond pulses at a rate of approximately 600 MHz. A spectral correlation across the multiwavelength spectrum which can be for utilizing single stripe laser diodes as multiwavelength sources in WDM-TDM networks. A third version of multiple wavelength generation uses a fiber-array and grating. And a fourth version of wavelength generation uses a Fabry-Perot Spectral filter. Also solid state laser sources and optical fiber laser sources can be used

Compact and low-cost ultrashort-pulse Ti:sapphire lasers

The subject matter of this thesis centres around the design and development of ultrafast Ti:sapphire lasers in a compact and low-cost context. Using 450 nm laser diodes as the pump source, both semiconductor saturable absorber mirror (SESAM) mode-locking and Kerr-lens mode-locking (KLM) techniques are used. Broad wavelength tunability while maintaining femtosecond pulse operation at 100’s of mW of average power and 10’s of kW of peak power was demonstrated. In the SESAM mode-locked configuration, a wavelength tunability range of 37 nm (788-825 nm) was demonstrated, with average output powers up to 433 mW, and with shortest pulse duration of 62 fs at 812 nm. In the KLM regime, a wavelength tunability range of 120 nm (755-875 nm) was demonstrated, with average output powers up to 382 mW, and with shortest pulse duration of 54 fs at 810 nm. Various cavity configurations were proposed and analysed with the intention of realising GHz pulse repetition rates in an ultrafast diode-pumped Ti:sapphire laser. Two different cavity configurations were chosen: KLM in a ring resonator configuration and SESAM mode-locking in a Z-shape standing-wave resonator configuration. Efficient continuous wave operation was achieved, however, mode-locked operation was not reached with either configuration. Graphene saturable absorbers for femtosecond pulse generation in diode-pumped Ti:sapphire were also investigated. Monolayer graphene samples were fully characterised in a differential transmission setup. This resulted in a saturation fluence of (41± 27) μJ/cm2, a saturable loss of (1.01 ± 0.15)% and a non-saturable loss of (0.42 ± 0.09)%, in broad agreement with values reported in the literature. The diode-pumped Ti:sapphire laser sources developed during the course of this thesis have demonstrated important performance parameters that bring them closer to matching the performance of their conventionally pumped counterparts, namely a wide wavelength tunability while maintaining femtosecond pulse operation at 100’s of mW of average power and 10’s of kW of peak power, suitable for many applications.The subject matter of this thesis centres around the design and development of ultrafast Ti:sapphire lasers in a compact and low-cost context. Using 450 nm laser diodes as the pump source, both semiconductor saturable absorber mirror (SESAM) mode-locking and Kerr-lens mode-locking (KLM) techniques are used. Broad wavelength tunability while maintaining femtosecond pulse operation at 100’s of mW of average power and 10’s of kW of peak power was demonstrated. In the SESAM mode-locked configuration, a wavelength tunability range of 37 nm (788-825 nm) was demonstrated, with average output powers up to 433 mW, and with shortest pulse duration of 62 fs at 812 nm. In the KLM regime, a wavelength tunability range of 120 nm (755-875 nm) was demonstrated, with average output powers up to 382 mW, and with shortest pulse duration of 54 fs at 810 nm. Various cavity configurations were proposed and analysed with the intention of realising GHz pulse repetition rates in an ultrafast diode-pumped Ti:sapphire laser. Two different cavity configurations were chosen: KLM in a ring resonator configuration and SESAM mode-locking in a Z-shape standing-wave resonator configuration. Efficient continuous wave operation was achieved, however, mode-locked operation was not reached with either configuration. Graphene saturable absorbers for femtosecond pulse generation in diode-pumped Ti:sapphire were also investigated. Monolayer graphene samples were fully characterised in a differential transmission setup. This resulted in a saturation fluence of (41± 27) μJ/cm2, a saturable loss of (1.01 ± 0.15)% and a non-saturable loss of (0.42 ± 0.09)%, in broad agreement with values reported in the literature. The diode-pumped Ti:sapphire laser sources developed during the course of this thesis have demonstrated important performance parameters that bring them closer to matching the performance of their conventionally pumped counterparts, namely a wide wavelength tunability while maintaining femtosecond pulse operation at 100’s of mW of average power and 10’s of kW of peak power, suitable for many applications

New methods to generate wavelength-tunable pulses from semiconductor and fiber lasers using the dispersion tuning approach.

Lee Ka-lun.Thesis (M.Phil.)--Chinese University of Hong Kong, 2000.Includes bibliographical references.Abstracts in English and Chinese.Abstract --- p.iiAcknowledgment --- p.vTable of contents --- p.viList of figure --- p.viiiChapter 1. --- Introduction --- p.1Chapter 1.1. --- Generation of picosecond pulses from semiconductor laser and fiber laser --- p.2Chapter 1.2. --- Wavelength tunable pulse generated from semiconductor laser --- p.5Chapter 1.3. --- Wavelength tunable pulse generated from erbium doped fiber laser --- p.7Chapter 1.4. --- Structure of the thesis --- p.8Chapter 2. --- Principles and Theories --- p.13Chapter 2.1. --- Principle of dispersion tuning --- p.15Chapter 2.1.1. --- Dependence on the strength of dispersion --- p.16Chapter 2.1.2. --- Wavelength selection in time domain --- p.18Chapter 2.1.3. --- Compensated dispersion tuning in a dispersion balanced fiber ring --- p.20Chapter 2.2. --- Optical gating using Nonlinear Optical Loop Mirror (NOLM) incorporated with nonlinear element --- p.22Chapter 2.3. --- Principle of compensated dispersion tuning in harmonically mode- locked fiber laser incorporated with linearly chirped fiber grating (LCFG) --- p.26Chapter 2.4. --- Principle of compensated dispersion tuning in self-seeding configuration --- p.29Chapter 2.5. --- Principle of dual-wavelength operation in harmonically mode-locked fiber laser --- p.31Chapter 3. --- Preliminarily experimental study --- p.33Chapter 3.1. --- Wavelength selection using strong and weak dispersive medium --- p.34Chapter 3.2. --- NOLM as a fast optical modulator --- p.38Chapter 4. --- Self-compensated dispersion-tuning in mode-locked fiber laser using bi- directional transit in a linearly chirped fiber grating --- p.41Chapter 4.1. --- Introduction --- p.42Chapter 4.2. --- Experimental Details --- p.43Chapter 4.3. --- Results and discussion --- p.47Chapter 4.4. --- Summary --- p.54Chapter 5. --- Generation of wavelength tunable pulses from a self-seeded semiconductor laser using an optically controlled Nonlinear Optical Loop Modulator (NOLM) incorporated with a Semiconductor Optical Amplifier (SOA) --- p.56Chapter 5.1. --- Introduction --- p.57Chapter 5.2. --- Experimental Details --- p.58Chapter 5.3. --- Results and discussion --- p.64Chapter 5.4. --- Summary --- p.71Chapter 6. --- Alternate and Simultaneous Generation of 1 GHz Dual-Wavelength Pulses from an Electrically-Tunable Harmonically Mode-locked Fiber Laser --- p.74Chapter 6.1. --- Introduction --- p.75Chapter 6.2. --- Experimental Details --- p.76Chapter 6.3. --- Results and discussion --- p.80Chapter 6.4. --- Summary --- p.87Chapter 7. --- Conclusion and Future works --- p.89Chapter 7.1. --- Conclusion --- p.89Chapter 7.2. --- Future works --- p.93Appendix --- p.A-lList of Publication --- p.A-

High-purity microwave generation using a dual-frequency hybrid integrated semiconductor-dielectric waveguide laser

We present an integrated semiconductor-dielectric hybrid dual-frequency laser operating in the 1.5 $\mu$m wavelength range for microwave and terahertz (THz) generation. Generating a microwave beat frequency near 11 GHz, we observe a record-narrow intrinsic linewidth as low as about 2 kHz. This is realized by hybrid integration of a single diode amplifier based on indium phosphide (InP) with a long, low-loss silicon nitride (Si$_3$N$_4$) feedback circuit to extend the cavity photon lifetime, resulting in a cavity optical roundtrip length of about 30 cm on a chip. Simultaneous lasing at two frequencies is enabled by introducing an external control parameter for balancing the feedback from two tunable, frequency-selective Vernier mirrors on the Si$_3$N$_4$ chip. Each frequency can be tuned with a wavelength coverage of about 80 nm, potentially allowing for the generation of a broad range of frequencies in the microwave range up to the THz range

Advanced pulsed and long-wavelength semiconductor lasers based on quantum-dot and antimonide materials

In this thesis mid-infrared optically-pumped semiconductor disk laser (OP-SDL) emitting at 2.5 µm is developed for the very first time. Although laser diodes at this wavelength have already been reported, the motivation of this experiment is to extend the first SDL to this region. The advantage of SDLs over laser diodes is their superior beam quality with high powers, and practical potential for wavelength tuning. These properties are a great asset in many applications such as chemical sensing, biomedicine, thermal imaging and spectroscopy. Mode-locked quantum dot edge-emitting lasers emitting at 1.2 µm and 1.3 µm are also investigated in this thesis. The purpose of these experiments is to use them as master oscillator for bismuth doped fiber amplifiers, operating at 1.2–1.3 µm. The motivation of these experiments was to build a compact system to achieve amplified short pulses with good beam quality. Studies in this thesis were carried out experimentally. First, the SDL chip was processed and build into a laser. Then the laser output properties were measured with various instruments. For the first time, a GaSb-based OP-SDL operating at 2.5 µm spectral range has been demonstrated. The laser operated in continuous wave as well as tunable laser. With an intra-cavity diamond heat spreader used for thermal management, 600 mW of continuous wave output power has been achieved with good beam quality. Tunable operation with 130 nm tuning range and output power up to 310 mW has been obtained, limited by the free spectral range and loss induced by the etalon. As a conclusion, the obtained results show that the advantages of high-power disk laser technology can be extended to 2.5 µm and beyond utilizing (AlGaIn)(AsSb) semiconductor compounds. This material system was found to provide both wide band low loss mirrors and wide gain desired for tunable lasers. These characteristics allow high power and high brightness to be achieved. The mode-locked edge-emitting quantum-dot lasers operating at 1.2 µm and 1.3 µm spectral range have been characterized in detail. For the 1.2 µm laser diode, the optimum performance resulted in 71 mW of average output power with 5.56 ps pulse width and 30.45 GHz repetition rate. Respectively, the 1.3 µm laser diode reached 20.4 mW of output power and 8.3 ps pulse width at 10.2 GHz pulse repetition rate. For both laser diodes stable mode-locking was found to originate from ground state lasing. As a conclusion, it is shown that mode-locked edge-emitting lasers can be used as a compact ultra fast seed signal source for Bi-fiber amplifiers. Although the seed lasers themselves operated as planned, it was concluded that the Bi-amplifiers would still need further development

Unlocking Spectral Versatility from Broadly-Tunable Quantum-Dot Lasers

Wavelength−tunable semiconductor quantum−dot lasers have achieved impressive performance in terms of high−power, broad tunability, low threshold current, as well as broadly tunable generation of ultrashort pulses. InAs/GaAs quantum−dot−based lasers in particular have demonstrated significant versatility and promise for a range of applications in many areas such as biological imaging, optical fiber communications, spectroscopy, THz radiation generation and frequency doubling into the visible region. In this review, we cover the progress made towards the development of broadly−tunable quantum−dot edge−emitting lasers, particularly in the spectral region between 1.0–1.3 µm. This review discusses the strategies developed towards achieving lower threshold current, extending the tunability range and scaling the output power, covering achievements in both continuous wave and mode−locked InAs/GaAs quantum−dot lasers. We also highlight a number of applications which have benefitted from these advances, as well as emerging new directions for further development of broadly−tunable quantum−dot lasers