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Noncontact Liquid Crystalline Broadband Optoacoustic Sensors, Hengky Chandrahalim, Michael T. Dela Cruz
Noncontact Liquid Crystalline Broadband Optoacoustic Sensors, Hengky Chandrahalim, Michael T. Dela Cruz
AFIT Patents
An optoacoustic sensor includes a liquid crystal (LC) cell formed between top and bottom plates of transparent material. A transverse grating formed across the LC cell that forms an optical transmission bandgap. A CL is aligned to form a spring-like, tunable Bragg grating that is naturally responsive to external agitations providing a spectral transition regime, or edge, in the optical transmission bandgap of the transverse grating that respond to broadband acoustic waves. The optoacoustic sensor includes a narrowband light source that is oriented to transmit light through the top plate, the LC cell, and the bottom plate. The optoacoustic sensor …
Atmospheric Propagation Of High Energy Lasers: Thermal Blooming Simulation, Jonathan Gustafsson, Benjamin F. Akers, Jonah A. Reeger, Sivaguru S. Sritharan
Atmospheric Propagation Of High Energy Lasers: Thermal Blooming Simulation, Jonathan Gustafsson, Benjamin F. Akers, Jonah A. Reeger, Sivaguru S. Sritharan
Faculty Publications
High Energy Laser (HEL) propagation through turbulent atmosphere is examined via numerical simulation. The beam propagation is modeled with the paraxial equation, which in turn is written as a system of equations for a quantum fluid, via the Madelung transform. A finite volume solver is applied to the quantum fluid equations, which supports sharp gradients in beam intensity. The atmosphere is modeled via a coupled advection-diffusion equation whose initial data have Kolmogorov spectrum. In this model the combined effects of thermal blooming, beam slewing, and deep turbulence are simulated.
Two-Photon Excitation Of Cesium Alkali Metal Vapor 72D, 82D Kinetics And Spectroscopy, Ricardo C. Davila
Two-Photon Excitation Of Cesium Alkali Metal Vapor 72D, 82D Kinetics And Spectroscopy, Ricardo C. Davila
Theses and Dissertations
Pulsed excitation on the two-photon Cs 62S½ → 72D3/2,5/2 transition results in time-resolved fluorescence at 697 nm and 672 nm. The rates for fine structure mixing between the 72D3/2,5/2 states have been measured for helium and argon rare gas collision partners. The mixing rates are very fast, 1.26 ± 0.05 x 10-9 cm3/(atom sec) for He and 1.52 ± 0.05 x 10-10 cm3 /(atom sec) for Ar, driven by the small energy splitting and large radial distribution for the valence electron. …
Kinetics Of Higher Lying Rb States After, Pulsed Excitation Of The D2 Transition In The Presence Of Helium, Austin J. Wallerstein
Kinetics Of Higher Lying Rb States After, Pulsed Excitation Of The D2 Transition In The Presence Of Helium, Austin J. Wallerstein
Theses and Dissertations
The Diode Pumped Alkali Laser (DPAL) is a high power, three-level laser system that employs diode bars to optically excite an alkali metal vapor. It lases along the D1 transition, between the two lowest energy levels, 2P1/2 and 2S1/2. Higher lying energy states are produced at higher population density via energy pooling and multiphoton processes. Pulsed laser excitation of rubidium at approximately 1 MW=cm2 has been studied at helium pressure up to 900 Torr. Emissions from energy states as high as 82D suggests modest ionization, though these intensities decrease drastically at buffer gas …
Fusion Of Renewable Ring Resonator Lasers And Ultrafast Laser Inscribed Photonic Waveguides, Hengky Chandrahalim, Stephen C. Rand, Xudong Fan
Fusion Of Renewable Ring Resonator Lasers And Ultrafast Laser Inscribed Photonic Waveguides, Hengky Chandrahalim, Stephen C. Rand, Xudong Fan
Faculty Publications
We demonstrated the monolithic integration of reusable and wavelength reconfigurable ring resonator lasers and waveguides of arbitrary shapes to out-couple and guide laser emission on the same fused-silica chip. The ring resonator hosts were patterned by a single-mask standard lithography, whereas the waveguides were inscribed in the proximity of the ring resonator by using 3-dimensional femtosecond laser inscription technology. Reusability of the integrated ring resonator – waveguide system was examined by depositing, removing, and re-depositing dye-doped SU-8 solid polymer, SU-8 liquid polymer, and liquid solvent (toluene). The wavelength reconfigurability was validated by employing Rhodamine 6G (R6G) and 3,3′-Diethyloxacarbocyanine iodide (CY3) …
Monolithic Optofluidic Ring Resonator Lasers Created By Femtosecond Laser Nanofabrication, Hengky Chandrahalim, Qiushu Chen, Ali A. Said, Mark Dugan, Xudong Fan
Monolithic Optofluidic Ring Resonator Lasers Created By Femtosecond Laser Nanofabrication, Hengky Chandrahalim, Qiushu Chen, Ali A. Said, Mark Dugan, Xudong Fan
Faculty Publications
We designed, fabricated, and characterized a monolithically integrated optofluidic ring resonator laser that is mechanically, thermally, and chemically robust. The entire device, including the ring resonator channel and sample delivery microfluidics, was created in a block of fused-silica glass using a 3-dimensional femtosecond laser writing process. The gain medium, composed of Rhodamine 6G (R6G) dissolved in quinoline, was flowed through the ring resonator. Lasing was achieved at a pump threshold of approximately 15 μJ/mm2. Detailed analysis shows that the Q-factor of the optofluidic ring resonator is 3.3 × 104, which is limited by both solvent …
Reconfigurable Solid-State Dye-Doped Polymer Ring Resonator Lasers, Hengky Chandrahalim, Xudong Fan
Reconfigurable Solid-State Dye-Doped Polymer Ring Resonator Lasers, Hengky Chandrahalim, Xudong Fan
Faculty Publications
This paper presents wavelength configurable on-chip solid-state ring lasers fabricated by a single-mask standard lithography. The single- and coupled-ring resonator hosts were fabricated on a fused-silica wafer and filled with 3,3′-Diethyloxacarbocyanine iodide (CY3), Rhodamine 6G (R6G) and 3,3′-Diethylthiadicarbocyanine iodide (CY5)-doped polymer as the reconfigurable gain media. The recorded lasing threshold was ~220 nJ/mm2 per pulse for the single-ring resonator laser with R6G, marking the lowest threshold shown by solid-state dye-doped polymer lasers fabricated with a standard lithography process on a chip. A single-mode lasing from a coupled-ring resonator system with the lasing threshold of ~360 nJ/mm2 per pulse …
Iron-Doped Zinc Selenide: Spectroscopy And Laser Development, Jonathan W. Evans
Iron-Doped Zinc Selenide: Spectroscopy And Laser Development, Jonathan W. Evans
Theses and Dissertations
We examine the quantum mechanics of optically active ions in crystals. Insight is developed which qualitatively explains the shape of the optical absorption and emission spectra of Fe2+ ions in II-VI materials. In addition to a discussion of the relevant theory, this work explores experimental techniques for absorption spectroscopy, laser-induced fluorescence spectroscopy, and upper-state lifetime measurements in detail. The data collected from these experiments are interpreted in the context of the theories developed herein. The theory and data are used to develop a simple model of the temperature dependence of the upper-state lifetime of Fe2+ ions in ZnSe. …
Tunable Optical Delay In Doppler-Broadened Cesium Vapor, Monte D. Anderson
Tunable Optical Delay In Doppler-Broadened Cesium Vapor, Monte D. Anderson
Theses and Dissertations
Variable-delay tunable optical delay line or optical buffers are critical for the development of all-optical networks components as well as interferometry and analytic instruments. Recent research on slow light may hold the key for the development of the first practical tunable optical delay device. In this research the linear dispersion delay effects in an alkali vapor. The hyperfine relaxation observations present insight into the complex bleach wave dynamics during a high-intensity pulsed pump in DPAL systems.
Rubidium Recycling In A High Intensity Short Duration Pulsed Alkali Laser, Wooddy S. Miller
Rubidium Recycling In A High Intensity Short Duration Pulsed Alkali Laser, Wooddy S. Miller
Theses and Dissertations
Laser induced fluorescence was used to study how pump pulse duration and alkali recycle time effects maximum power output in a Diode Pumped Alkali Laser (DPAL) system. A high intensity short pulsed pump source was used to excited rubidium atoms inside a DPAL-type laser. The maximum output power of the laser showed a strong dependence upon the temporal width of the pump pulse in addition to the input pump intensity. A linear relationship was observed between the maximum output power and the pulse width due to the effective lifetime of the excited state, defined as the time it takes for …
Q-Switched And Mode Locked Short Pulses From A Diode Pumped, Yb-Doped Fiber Laser, Seth M. Swift
Q-Switched And Mode Locked Short Pulses From A Diode Pumped, Yb-Doped Fiber Laser, Seth M. Swift
Theses and Dissertations
A diode-pumped, ytterbium (Yb)-doped fiber laser system was designed and demonstrated to operate in continuous wave (cw), passively Q-switched and possibly passively mode locked operation. To our knowledge, this was the first fiber laser oscillator built at the Air Force Institute of Technology. A Cr4+:YAG (Chromium: Ytterbium Aluminum Garnett) crystal was used as a saturable absorber to generate Q-switched pulses. Attempts to mode lock the laser were performed using a semiconductor saturable absorber mirror (SESAM) and through nonlinear polarization rotation (NPR). The best output power result was 5 Watts (W) while pumping at 8.3 W, yielding 60% efficiency …
Demonstration Of A Strategy To Perform Two-Dimensional Diode Laser Tomography, Ryan N. Givens
Demonstration Of A Strategy To Perform Two-Dimensional Diode Laser Tomography, Ryan N. Givens
Theses and Dissertations
Demonstration of a strategy to perform two-dimensional diode laser tomography using a priori knowledge from symmetry arguments and computational fluid dynamic (CFD) calculations is presented for a flat flame burner. The strategy uses an optimization technique to determine flame diameter and location using a vector quantization approach. Next, the variance in a training set, produced from CFD calculations, is captured using principal components analysis. The information in the training set allows interpolation between beam paths resulting in temperature and density maps. Finally, the TDLAS temperature and density maps are shown to agree with traditional thermocouple measurements of the flat flame …
Time Resolution Of Collapse Events During The Progation Of Ultraviolet Filaaments, Teresa J. Fondren
Time Resolution Of Collapse Events During The Progation Of Ultraviolet Filaaments, Teresa J. Fondren
Theses and Dissertations
Long distance propagation, or filamentation, of short, intense laser pulses is suggested to be possible through the balance of two effects: self-focusing, when a nonlinear index of refraction of air is induced by high intensities, and de-focusing, due to the plasma created by the pulse. Applications for filamentation include areas such as remote sensing and directed energy. A split-step spectral propagation simulation is used to model the behavior of a high intensity ultraviolet laser pulse propagating through air. Convergence of femtosecond duration collapses that form on the leading edge of the pulse in the time domain is achieved with an …
Direct Diode Pumped Raman Amplifier Based On A Multimode Graded Index Fiberr, Charles James Baird
Direct Diode Pumped Raman Amplifier Based On A Multimode Graded Index Fiberr, Charles James Baird
Theses and Dissertations
The direct pumping of a Raman fiber amplifier (RFA) was attempted using an array of four 25W, fiber pigtailed diodes at 936nm, combined via a 7 channel fiber beam combiner. The initial attempt was conducted using a 1.8 km, 100 micron core, GRIN fiber with an NA of .29 and attenuation 3.6 dB/km at 936nm. While amplification was not achieved, over 200mW of conversion was shown, with 10.4W of pump power and 3.5W of seed. This corresponds to an average conversion efficiency of 2.2%. The subsequent effort utilized a 2km long, 200 micron core, GRIN fiber, with NA of .27 …
Comparison Of Climatological Optical Turbulence Profiles To Standard, Statistical And Numerical Models Using Heleeos, Liesebet E. Gravley
Comparison Of Climatological Optical Turbulence Profiles To Standard, Statistical And Numerical Models Using Heleeos, Liesebet E. Gravley
Theses and Dissertations
Optical turbulence within earth’s atmosphere plays a significant role in electromagnetic radiation propagation from a high energy laser. The index of refraction structure constant, Cn2, characterizes turbulent spatial fluctuations due to temperature gradients. These changes in the index of refraction affect the intensity of the laser wave front on its intended target. It is important to characterize this parameter throughout the atmosphere, the boundary layer and above, for its applications regarding the Airborne Laser (ABL) and the Advanced Tactical Laser (ATL). There are several ways to obtain values of optical turbulence, including standard and statistical models, physically-based numerical models, and …
Phasing A Dual Optical Path System Using An Optical Fiber As A Phase Conjugate Mirror, Shawn M. Willis
Phasing A Dual Optical Path System Using An Optical Fiber As A Phase Conjugate Mirror, Shawn M. Willis
Theses and Dissertations
Phase conjugation properties of stimulated Brillouin scattering (SBS) in a short multimode fiber have been investigated with an eye towards its application for a multi-channel double pass master oscillator power amplifier (MOPA) system. In particular, properties of the SBS beam to compensate for the axial and transverse phase distortion between individual channels in a multi-channel amplifier system were studied. Two optical paths were created by covering half of the laser beam with a microscope slide, and also by spatially splitting the wavefronts with a 4 prism set-up. The Stokes beams that traversed the same optical paths as the pump beams …
Algorithm Development For On-Line Control Of The Airborne Laser, Michael W. Oppenheimer
Algorithm Development For On-Line Control Of The Airborne Laser, Michael W. Oppenheimer
Theses and Dissertations
The use of adaptive optics entails the design of a controller. This requires the development of a model of the plant to be controlled, which, in this case, Consists of the atmosphere through which light is traveling. In optics, Zemike polynornials are used as a basis set for the expansion of wavefront phase distortions. Due to the turbulence induced stochastic nature of the underlying process involved, the spatial-temporal correlation functions of the Zemike polynomial phase expansion coefficients must be evaluated if a proper stochastic model of the plant is to be developed and adaptive optics is to be employed. In …