Bulletin of the American Physical Society
2005 Joint Spring Meeting Ohio Section of APS and the Southern Ohio Section of AAPT
Friday–Saturday, April 8–9, 2005; Dayton, OH
Session D5: Sources and Detectors |
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Chair: Andrew Sarangan Room: SC 150 |
Saturday, April 9, 2005 8:00AM - 8:12AM |
D5.00001: Exploring the terahertz region with a narrowband tunable source Peter Powers, Rashid Alkuwari, Joseph Haus The generation of widely tunable coherent terahertz (THz) frequencies is of great interest for a variety of applications in basic and applied sciences. This talk will present a narrow bandwidth approach to THz generation by means of difference frequency generation (DFG) between two optical parametric generators (OPG's). Since the OPG sources are narrow bandwidth and tunable, the DFG technique offers a pathway to tunable narrowband THz frequencies. The results based on DFG mixing the outputs from two OPG's in 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) show narrow-bandwidth operation from 1.6 to 4.5 THz. The utility of this system as a THz source will be demonstrated by showing the latest results of high-resolution transmission spectra for several materials. [Preview Abstract] |
Saturday, April 9, 2005 8:12AM - 8:24AM |
D5.00002: Thermal Lens Mitigation And Modeling In Chromium-Doped Zinc Selenide Laser Sources Patrick Berry, Kenneth Schepler, Peter Powers Cutting edge military and scientific applications require compact solid-state laser sources tunable in the 2-5 micron region. Divalent chromium-doped zinc selenide sources show great promise in this area but the development of these lasers has been hampered by their susceptibility to thermal lensing. A carefully chosen temperature management scheme can yield high returns in terms of reducing thermal issues. In order to reduce the experimental cost of investigating these designs, mathematical models of proposed thermal lensing solutions were produced using finite element analysis software and used to determine the best design for experimental verification. The chosen design, a pass-through pumped thin disk laser with dual windows, was simple to construct and showed no thermal issues for pulsed operation at suitable frequencies. This laser was made to demonstrate thermal issues at higher pulse repetition frequencies and lower outcoupler reflectivies. This type of laser was shown to be a good alternative to both the simple rod laser and the basic face-cooled thin disk laser. [Preview Abstract] |
Saturday, April 9, 2005 8:24AM - 8:36AM |
D5.00003: Fabrication and Direct Comparison of Periodically-Poled Materials for Mid-Ir Generation Eric Vershure This work presents a comparison between nonlinear crystals used for frequency conversion, including congruent lithium niobate, stoichiometric lithium niobate, and stoichiometric lithium tantalate. Periodically-poled materials were fabricated using a refined process that allowed us to efficiently electric-field pole stoichiometric samples as thick as 2.0 mm. Comparisons between the different materials were made by viewing the poled domains after etching as well as by measuring the wavelength, bandwidth, threshold, and slope efficiency created via optical parametric generation (OPG). The OPG process generated wavelengths ranging from 1.3 to 1.7 microns in the signal and 2.6 to 5.0 microns in the idler when pumped with 1.064 microns. Material absorption hindered idler wavelength generation beyond 5 microns. Bandwidths and slope efficiencies were similar for the three materials, and effective thresholds were proportional to the inverse-square of the effective nonlinear coefficient. A further measurement of poling quality was made by probing the efficiency as a function of depth in 2.0-mm thick samples. This measurement indicated that poling quality near the original ``+z'' surface of the crystals, where domain reversal begins during poling, was significantly better than that near the ``-z'' surfaces. Based on ease-of-fabrication and ability to generate long wavelengths, we recommend periodically-poled stoichiometric lithium niobate for applications in mid-IR frequency conversion. [Preview Abstract] |
Saturday, April 9, 2005 8:36AM - 8:48AM |
D5.00004: Fabrication of Granular Aluminum Microbolometers -- Solving the Contact Resistance Problem Thomas Wilson The fabrication of granular aluminum superconducting bolometers with a $\sim $10 ns response time and an active area of 10 micron x 20 micron will be described. Photomask design, the photolithographic and sputtering processing steps will be discussed in detail. Reproducible bolometers with room temperature resistances of 10-Ohms are routinely obtained. In particular, the common problem of the oxidation of the granular aluminum prior to the deposition of the electrical contact pads has been solved by sputtering a thin ($\sim $50 angstroms) palladium protective layer over the aluminum prior to exposure to air. [Preview Abstract] |
Saturday, April 9, 2005 8:48AM - 9:00AM |
D5.00005: Characterization of carrier drift and diffusion in an InSb focal plane array under high-intensity excitation Bryant Wysocki, Michael Marciniak, Mitchell Haeri A study of blooming effects in a 640 x 480 indium-antimonide (InSb) focal plane array (FPA) with 20-$\mu $m pixel-to-pixel spacing and operated at 77 K is presented. Electronic and optical blooming from both a high-intensity blackbody spectral source and a 4.6 $\mu $m narrow line-width laser source is examined. A 30-$\mu $m pinhole/mask was fastened directly to the FPA to achieve spatial isolation of individual pixels in an attempt to separate optical and electronic effects. A series of experiments both with and without the mask present was run to determine the relative contributions of each. Images were captured and analyzed. Optical effects caused by ghosting, diffraction, and lens and housing scatter were shown to dominate, resulting in global loss of image quality. It was determined that global saturation is primarily caused by scattering generated in the optics of the imaging system and the dewar window. Effects due to electronic phenomenon, such as carrier diffusion and charge bleeding, were shown to be minimal and locally constrained to $\sim $20 $\mu $m. A simple model of carrier drift and diffusion was constructed to provide a theoretical model of the crosstalk between pixels. [Preview Abstract] |
Saturday, April 9, 2005 9:00AM - 9:12AM |
D5.00006: The Effects of Photo-Generated Carrier Diffusion on Blooming in an IR Detection System Exposed to High Intensity Sources Bryant Wysocki, Michael Marciniak, Mitchell Haeri Extremely sensitive focal plane arrays (FPA's) with high spatial resolution play an ever-increasing role in infrared imaging. Military and intelligence operations rely heavily on the information gathered by these systems, requiring them to be hardened against enemy countermeasures. A study of the blooming effects in a 640 x 480 indium-antimonide (InSb) FPA with 20 $\mu $m pixel-to-pixel spacing and operated at 77 K is presented. Electronic and optical blooming from both a high-intensity blackbody spectral source and a 4.6 $\mu $m narrow line-width laser source is examined. A 30-$\mu $m pinhole/mask was fastened directly to the FPA to achieve spatial isolation of individual pixels in an attempt to separate optical and electronic effects. A series of experiments were run to determine the relative contributions of each. The spectral source and the laser were each used to bloom the FPA both with and without the mask present. Optical effects caused by ghosting, diffraction, lens and housing scatter were shown to dominate, resulting in global loss of image quality. Effects due to electronic phenomenon, such as carrier diffusion and charge bleeding, were shown to be minimal and locally constrained to $\sim $ 20 $\mu $m. A simulation of carrier drift and diffusion was constructed to provide a theoretical model of the crosstalk between pixels. [Preview Abstract] |
Saturday, April 9, 2005 9:12AM - 9:24AM |
D5.00007: Resonant cavity enhanced (RCE) corrugated quantum well infrared photodetectors (C-QWIP) Jang Pyo Kim, Aziz Mahfoud, Andrew Sarangan Corrugated quantum well infrared photodetector (C-QWIP) provides some advantages over the grating-coupled quantum well infrared photodetector (QWIP). Since it operates based on reflection rather than diffraction, the corrugated coupling scheme is both pixel-size and wavelength-independent. In the QWIP structure, however, only light with electric field component perpendicular to the QW layers can be absorbed due to the dipole selection rule. To alleviate this problem, C-QWIP uses the total internal reflection (TIR) to redirect the light into the QW detector. In this way, one can rotate the electric field component perpendicular to the layers for 50{\%} of the incident unpolarized photons. Even though the quantum efficiency of C-QWIP is higher than grating couplers, it still lags behind competing technologies such as HgCdTe, which have nearly 100{\%} efficiency because they do not suffer from the polarization selection rule. We considered an alternative design that utilizes a resonant cavity that allows for multiple passes of photons through the active region in order to increase the absorption probability and hence increase the QE and reduce the dark current. In this paper, we present the simulation result for the resonant cavity enhanced (RCE) C-QWIP structures using multi-layer Bragg stacks as reflecting elements. [Preview Abstract] |
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