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Full-Text Articles in Physics
Electroluminescence Studies On Longwavelength Indium Arsenide Quantum Dot Microcavities Grown On Gallium Arsenide, John C. Ramsey
Electroluminescence Studies On Longwavelength Indium Arsenide Quantum Dot Microcavities Grown On Gallium Arsenide, John C. Ramsey
Theses and Dissertations
A comprehensive study of the electroluminescence of four GaAs/AlGaAs microcavity devices with InAs/GaInAs quantum dot active regions emitting near 1.3 µm was conducted. The four molecular beam epitaxial grown samples with AlAs oxide aperture confinement layers were fabricated, characterized, and optically modeled. Optical power transmission of the samples was modeled using Matlab and compared with measured transmission data. Resonant cavity light emitting diodes (RCLEDs) and three vertical cavity surface emitting laser (VCSEL) samples were fabricated and electro-optically characterized over a range of injection currents and temperatures. Devices achieved continuous wave room temperature lasing at 1.28 µm with an output power …
Modulation Response Of Twin Optically Coupled Diode Lasers, Eric M. Golden
Modulation Response Of Twin Optically Coupled Diode Lasers, Eric M. Golden
Theses and Dissertations
Diode lasers are useful in military and commercial applications that have strict requirements for size, weight and power. This includes the use of diode lasers in optoelectronic and photonic integrated circuits, which can lead to new technologies in optical communications and optical interconnects in high performance computing systems. For these systems to be effective, the diode laser must be modulated at frequencies beyond current limits which are typically a few GHz. This barrier can be broken by optically coupling a diode laser with a similar laser. A set of single mode rate equations models the dynamics of twin optically coupled …
Ultrafast Spectroscopy Of Mid-Infrared Semiconductors Using The Signal And Idler Beams Of A Synchronous Optical Parametric Oscillator, Richard M. Derbis
Ultrafast Spectroscopy Of Mid-Infrared Semiconductors Using The Signal And Idler Beams Of A Synchronous Optical Parametric Oscillator, Richard M. Derbis
Theses and Dissertations
Mid-Wave Infrared (MWIR) semiconductors are of use to the Air Force for several applications. Ultrafast spectroscopy can be used to better quantify the effectiveness of semiconductor opto-electronic devices. The objective of this thesis was to improve the procedure for taking ultrafast, time-resolved measurements of photoluminescence from MWIR semiconductors. Previous work has used a mode-locked titanium sapphire (Ti:Saph) laser to excite the semiconductor sample and to upconvert the photoluminescence from the semiconductor. Work completed in this thesis improved on the techniques developed during previous work. A synchronous Optical Parameter Oscillator (OPO) will be used to convert the Ti:Saph laser (0.830 µm) …
Backward Amplification And Beam Cleanup Of A Raman Fiber Laser Oscillator Using A Multi-Mode Graded Index Fiber Amplifier, Jesse D. S. Morgan Iii
Backward Amplification And Beam Cleanup Of A Raman Fiber Laser Oscillator Using A Multi-Mode Graded Index Fiber Amplifier, Jesse D. S. Morgan Iii
Theses and Dissertations
This thesis tested a CW fiber-based Raman amplifier implemented in a backward pumped geometry. To create a seed for the amplifier, a CW Nd:YAG laser operating at 1.064µm was used to pump a 50µm multimode graded index fiber using fiber Bragg gratings to create a Raman Fiber Laser (RFL) Oscillator with a Stokes beam at 1.116µm. The Stokes beam was then used to seed two lengths, 5.3km and 2.5km, of 50µm multimode graded index fiber. The fiber amplifier was pumped by a second CW Nd:YAG laser in the backward geometry. Spectral data taken for both fibers indicated that the backward …
Optical Characterization Of Antimony-Based, Types-I And Ii, Multiple Quantum-Well Semiconductor Structures For Mid-Infrared Laser Applications, Edward G. Ferguson
Optical Characterization Of Antimony-Based, Types-I And Ii, Multiple Quantum-Well Semiconductor Structures For Mid-Infrared Laser Applications, Edward G. Ferguson
Theses and Dissertations
This experiment characterizes antimony-based, multiple quantum-well, types-I and -II, semiconductor samples designed for laser applications. The samples emit light in the 3-5-micron range to exploit an atmospheric transmission window, making them ideal for infrared (IR)-seeking missile countermeasures. Photoluminescence (PL) spectra were collected and yielded bandgap (E(sub g)) dependence-on-temperature relationships. The type-I sample was found to follow the Varshni equation, while the type-II samples showed a rise with temperature in a portion of the curve that should be linear according to the Varshni equation. The type-II samples followed the Varshni equation well at higher temperature. The PL study indicated that the …
Carrier Dynamics In Mid-Infrared Quantum Well Lasers Using Time-Resolved Photoluminescence, Steven M. Gorski
Carrier Dynamics In Mid-Infrared Quantum Well Lasers Using Time-Resolved Photoluminescence, Steven M. Gorski
Theses and Dissertations
Research in mid-infrared laser technology has uncovered numerous applications for commercial and government use. A limiting factor for mid-infrared semiconductors is nonradiative recombination, which is a process that produces excess heat without emitting a photon. Nonradiative recombination mechanisms occur over a short time period and difficult to measure. Growth methods have significantly reduced the nonradiative recombination in some materials. The objective of this research is to further the understanding of how quantum well structures impact carrier recombination. InAsSb/InAlASb and InAs/GaInSb quantum well structures were studied with time-resolved photoluminescence utilizing upconversion, a non-linear wave mixing technique. This research reports Shockley-Read-Hall, radiative, …
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Time-Resolved Photoluminescence Of Inas/Gainsb Quantum Well Lasers, Michael R. Mckay
Theses and Dissertations
In the world of semiconductor photonic device fabrication, one important objective may be to extract as much light as possible from the device. In these devices, photons are created when electrons recombine with holes by transitioning from a high-energy state to a lower one. Unfortunately, electron-hole recombination does not always result in the formation of a photon. There are three basic types of recombination: the first results in the formation of a photon and is called radiative recombination; and the second and third, known as Shockley-Read-Hall and Auger recombination, result in the heating of the device and do not produce …
Optical Physics Of Microcavity Surface Emitting Lasers, Michael J. Noble
Optical Physics Of Microcavity Surface Emitting Lasers, Michael J. Noble
Theses and Dissertations
This dissertation consists of an in-depth theoretical analysis of the optical impact of transverse index confinement on the lasing modes of microcavity surface emitting lasers. Two different variational techniques were employed to calculate the relevant optical laser parameters: (1) modal resonance, field profile, (2) confinement factor, and (3) threshold gain. Through a semianalytic field analysis, two new confinement related effects were discovered: (1) a polarization dependent change in mirror reflectance with aperture radius, and (2) a mode dependent blueshift. Through a numerical field analysis, the physical mechanisms governing diffraction were ascertained. These are: (1) the transverse confinement of the optical …
Time Resolved Photoluminescence Spectra Of A Mid-Infrared Multiple Quantum Well Semiconductor Laser, Anthony L. Franz
Time Resolved Photoluminescence Spectra Of A Mid-Infrared Multiple Quantum Well Semiconductor Laser, Anthony L. Franz
Theses and Dissertations
Recombination mechanisms in mid-IR semiconductor lasers are strongly dependent on the carrier density of the active region. The objective of this research is to improve previous carrier density estimates through the incorporation of spectral information. One hundred photoluminescence (PL) spectra were calculated for a variety of carrier densities. Calculations were made for an InAsSb/InAlAsSb multiple quantum well laser sample assuming parabolic bands. The widths of the calculated spectral profiles were tabulated as a function of carrier density. Actual spectra were measured using the Ultrafast Mid-Infrared Photoluminescence System, which uses upconversion to measure the PL intensity in time steps smaller than …
Four-Wave Mixing And Optical Phase Conjugation In Vertical Cavity Surface Emitting Devices, Gregory J. Vansuch
Four-Wave Mixing And Optical Phase Conjugation In Vertical Cavity Surface Emitting Devices, Gregory J. Vansuch
Theses and Dissertations
Four-wave mixing (FWM), a nonlinear optical process, was investigated in resonant cavity light emitting diodes (RCLEDs) and vertical cavity surface emitting lasers (VCSELs) below lasing threshold. These semiconductor photonic devices consisted of an optical gain region of quantum wells sandwiched between two distributed Bragg reflector (DBR) mirrors. Pump and probe lasers were injected into the devices to generate FWM. The dependence of FWM on bias current, pump laser power, and spectral and spatial separation between pump and probe lasers was investigated experimentally. A computer model of FWM based on the wave and carrier density equations was developed and agreed well …
Experimental Investigation And Computer Modeling Of Optical Switching In Distributed Bragg Reflector And Vertical Cavity Surface Emitting Laser Structures, Richard J. Bagnell
Experimental Investigation And Computer Modeling Of Optical Switching In Distributed Bragg Reflector And Vertical Cavity Surface Emitting Laser Structures, Richard J. Bagnell
Theses and Dissertations
The optical switching capabilities of Distributed Bragg Reflector (DBR) structures, including Vertical Cavity Surface Emitting Lasers (VCSELs) are examined. Reflectivity switching is demonstrated using both thermal and carrier generated effects to alter the DBR/VCSEL layers' refractive indices. Optical bistability is demonstrated at room temperature, under CW photopumped excitation. The optical bistability hysteresis is controllable by spectral location of the pump on the stop band edge. In the VCSEL, reflective bistability is also evidenced; additionally, this bistability is accompanied by a bistability in the VCSEL lasing output intensity, spot size, and wavelength. Modeling of the DBR/VCSEL thermally induced bistability was accomplished …
Micromirror Array Control Of A Phase-Locked Laser Diode Array, Carl J. Christensen
Micromirror Array Control Of A Phase-Locked Laser Diode Array, Carl J. Christensen
Theses and Dissertations
A ten element micromirror array has been designed, fabricated, and employed to control the far field irradiance pattern of a phase locked laser diode array. The laser array used in this experiment was a ten element, gain guided array lasing at a nominal wavelength of 828 nm and operating in the it out of phase supermode. The laser's near field irradiance was imaged onto a micromirror array, where the it phase differences between adjacent laser elements were corrected. This was accomplished by moving the micromirrors with individually applied voltages. The result was the desirable single lobed far field pattern, placing …
Characterization Of Nonlinear Effects In Optically Pumped Vertical Cavity Surface Emitting Lasers, Scott L. Brown
Characterization Of Nonlinear Effects In Optically Pumped Vertical Cavity Surface Emitting Lasers, Scott L. Brown
Theses and Dissertations
The nonlinear characteristics of optically pumped Vertical Cavity Surface Emitting Lasers VCSELs are identified, isolated, and quantified. Three different VCSELs are evaluated including two with gain regions of bulk GaAs operating at 875nm and one multi-quantum well MQW InGaAs VCSEL operating at 950nm. The nonlinearities evaluated include those due to cavity temperature, carrier injection, and internal lasing field. The VCSELs are pumped by a picosecondfemtosecond TiSapphire laser which is configured to operate in CW, gated CW minimum gate width was 200ns, picosecond, and gated picosecond modes. A linear relationship is shown between wavelength and substrate temperature, cavity temperature, and injected …
Characterization Of An Lcd For Use As A Programmable Phase Shifter To Produce A Single-Lobed Far-Field Pattern In A Phased Array, Gregory S. Kenyon
Characterization Of An Lcd For Use As A Programmable Phase Shifter To Produce A Single-Lobed Far-Field Pattern In A Phased Array, Gregory S. Kenyon
Theses and Dissertations
The liquid crystal display LCD from an inexpensive pocket television was converted to a spatial light modulator SLM for the purpose of altering the phase front of a ten element diode laser array to produce a single lobe far field pattern. Characterization of the SLM determined the amount of phase shift, amplitude modulation and polarization rotation properties. Nonuniformities within the phase shifter and insufficient phase shift prevented the formation of a single lobe. However, a very limited phase grating was created and analyzed. LCDs from inexpensive commercial pocket televisions were found unsuitable for use as phase shifting spatial light modulators.
The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch
The Effects Of Optical Feedback On Polarization Of Vertical Cavity Surface Emitting Lasers, Gregory J. Vansuch
Theses and Dissertations
Vertical Cavity Surface Emitting Lasers VCSELs are a type of semiconductor laser with a cavity oriented orthogonally to the planes of material growth. These lasers differ from conventional edge emitting lasers in several important ways. They have symmetric output beams and they are easily built into two dimensional arrays, making them very attractive as photonic components. The characteristic of interest in this thesis is polarization. While the asymmetric cavities of edge emitters exhibit a clear preference for light polarized in a particular direction, the cylindrically symmetric cavity of a VCSEL has no clear preference. Therefore, it should be relatively easy …