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Cryogenic Optical Refrigeration, Seth Melgaard
Cryogenic Optical Refrigeration, Seth Melgaard
Optical Science and Engineering ETDs
This thesis compiles recent achievements in optical refrigeration, cooling a 5 wt. % ytterbium doped yttrium lithium fluoride (Yb+3:YLF) crystal through anti-Stokes fluorescence to a new record low temperature. This is the coldest temperature to date, without the use of cryogens or mechanical refrigerators, and is achieved by taking advantage of the Stark manifold resonance and high doping concentration available in a crystalline host. Cooling to \u223c155K from room temperature in a single stage with a cooling power of 90mW has been achieved, outperforming multi-stage Peltier coolers. Further cooling below the NIST-defined cryogenic temperature of 123K is shown feasible for …
Stimulated Brillouin Scattering Suppression Via Temperature Gradients In Fiber Amplifiers, Douglas Nelson
Stimulated Brillouin Scattering Suppression Via Temperature Gradients In Fiber Amplifiers, Douglas Nelson
Optical Science and Engineering ETDs
A method of improving the output power of a 177W narrow linewidth polarization maintaining ytterbium doped fiber amplifier is explored. The limiting factor, Stimulated Brillouin Scattering (SBS), is suppressed with a single-step temperature gradient. A similar fiber amplifier to the 177W amplifier is constructed and tested at various temperatures from 90C to -120C. The Brillouin frequency is observed to shift with temperature and the Brillouin spectrum splits into two peaks. These peaks correspond to the two temperatures that the fiber amplifier is exposed to and the separation between the peaks determines how strong the SBS suppression will be. Results of …
Novel Approaches To Power Scaling Of Single-Frequency Photonic Crystal Fiber Amplifiers, Craig Robin
Novel Approaches To Power Scaling Of Single-Frequency Photonic Crystal Fiber Amplifiers, Craig Robin
Optical Science and Engineering ETDs
This dissertation presents experimental and theoretical studies of high power, single-frequency, ytterbium-doped photonic crystal fiber amplifiers. The objective of this effort is to identify issues which limit power scaling and develop novel techniques to overcome these limitations. Historically, stimulated Brillouin scattering (SBS) has been the primary obstacle in the realization of high power single-frequency fiber amplifiers. A novel acoustically tailored photonic crystal fiber design, having a reduced Brillouin gain coefficient of 1.2x10-11 m/W, is demonstrated. The fiber design is such that it may be used in conjunction with other SBS mitigation techniques, which increases the nonlinear threshold beyond the current …
A Theoretical And Experimental Analysis Of Sbs Suppression Through Modification Of Amplifier Seed, Clint M. Zeringue
A Theoretical And Experimental Analysis Of Sbs Suppression Through Modification Of Amplifier Seed, Clint M. Zeringue
Optical Science and Engineering ETDs
Theoretical and experimental investigations of stimulated Brillouin scattering (SBS) are conducted in Yb-doped fiber amplifiers when the amplifier is simultaneously seeded with multiple distinct frequencies or with a phase modulated signal. To this end, detailed models of the SBS process are developed consisting of both a steady-state approach described mathematically by a coupled set of ordinary differential equations and also transient effects described by a coupled set of partial differential equations. For the multi-frequency seeded case, the equations are solved in the steady-state limit and include the effects of four-wave mixing (FWM), intrinsic and external thermal gradients, and laser gain. …
Microwave Techniques And Applications For Semiconductor Quantum Dot Mode-Locked Lasers, Chang-Yi Lin
Microwave Techniques And Applications For Semiconductor Quantum Dot Mode-Locked Lasers, Chang-Yi Lin
Optical Science and Engineering ETDs
Semiconductor mode-locked lasers (MLLs) are important as compact and cost-effective sources of picosecond or sub-picosecond optical pulses with moderate peak powers. They have potential use in various fields including optical interconnects for clock distribution at an inter-chip/intra-chip level as well as high bit-rate optical time division multiplexing (OTDM), diverse waveform generation, and microwave signal generation. However, there are still several challenges to conquer for engineering applications. Semiconductor MLLs sources have generally not been able to match the noise performance and pulse quality of the best solid-state mode-locked lasers. For improving the characteristics of semiconductor mode-locked lasers, research on both the …
Ultrafast Terahertz Spectroscopy And Control Of Collective Modes In Semiconductors, Denis Seletskiy
Ultrafast Terahertz Spectroscopy And Control Of Collective Modes In Semiconductors, Denis Seletskiy
Optical Science and Engineering ETDs
In this dissertation we applied methods of ultrafast terahertz (THz) spectroscopy to study several aspects of semiconductor physics and in particular of collective mode excitations in semiconductors. We detect and analyze THz radiation emitted by these collective modes to reveal the underlying physics of many-body interactions. We review a design, implementation and characterization of our ultrafast terahertz (THz) time-domain spectroscopy setup, with additional features of mid-infrared tunability and coherent as well as incoherent detection capabilities. Temperature characterization of the collective plasmon excitation in indium antimonide (InSb) is presented to reveal the importance of non-parabolicity corrections in quantitative description. We also …