A Hybrid Readout Solution for GaN-Based Detectors Using CMOS Technology.

Gallium nitride (GaN) and its alloys are becoming preferred materials for ultraviolet (UV) detectors due to their wide bandgap and tailorable out-of-band cutoff from 3.4 eV to 6.2 eV. GaN based avalanche photodiodes (APDs) are particularly suitable for their high photon sensitivity and quantum efficiency in the UV region and for their inherent insensitivity to visible wavelengths. Challenges exist however for practical utilization. With growing interests in such photodetectors, hybrid readout solutions are becoming prevalent with CMOS technology being adopted for its maturity, scalability, and reliability. In this paper, we describe our approach to combine GaN APDs with a CMOS readout circuit, comprising of a linear array of 1 × 8 capacitive transimpedance amplifiers (CTIAs), implemented in a 0.35 µm high voltage CMOS technology. Further, we present a simple, yet sustainable circuit technique to allow operation of APDs under high reverse biases, up to ≈80 V with verified measurement results. The readout offers a conversion gain of 0.43 µV/e-, obtaining avalanche gains up to 10³. Several parameters of the CTIA are discussed followed by a perspective on possible hybridization, exploiting the advantages of a 3D-stacked technology.

Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials.

Ultraviolet (UV) studies in astronomy, cosmology, planetary studies, biological and medical applications often require precision detection of faint objects and in many cases require photon-counting detection. We present an overview of two approaches for achieving photon counting in the UV. The first approach involves UV enhancement of photon-counting silicon detectors, including electron multiplying charge-coupled devices and avalanche photodiodes. The approach used here employs molecular beam epitaxy for delta doping and superlattice doping for surface passivation and high UV quantum efficiency. Additional UV enhancements include antireflection (AR) and solar-blind UV bandpass coatings prepared by atomic layer deposition. Quantum efficiency (QE) measurements show QE > 50% in the 100-300 nm range for detectors with simple AR coatings, and QE ≅ 80% at ~206 nm has been shown when more complex AR coatings are used. The second approach is based on avalanche photodiodes in III-nitride materials with high QE and intrinsic solar blindness.

First results from a dual photoelastic-modulator-based polarimetric camera.

We report on the construction and calibration of a dual photoelastic-modulator (PEM)-based polarimetric camera operating at 660?nm. This camera is our first prototype for a multispectral system being developed for airborne and spaceborne remote sensing of atmospheric aerosols. The camera includes a dual-PEM assembly integrated into a three-element, low-polarization reflective telescope and provides both intensity and polarization imaging. A miniaturized focal-plane assembly consisting of spectral filters and patterned wire-grid polarizers provides wavelength and polarimetric selection. A custom push-broom detector array with specialized signal acquisition, readout, and processing electronics captures the radiometric and polarimetric information. Focal-plane polarizers at orientations of 0 degrees and -45 degrees yield the normalized Stokes parameters q=Q/I and u=U/I respectively, which are then coregistered to obtain degree of linear polarization (DOLP) and angle of linear polarization. Laboratory test data, calibration results, and outdoor imagery acquired with the camera are presented. The results show that, over a wide range of DOLP, our challenging objective of uncertainty within +/-0.005 has been achieved.

A Spanish language and culture initiative for a doctor of pharmacy curriculum.

OBJECTIVE: To implement a Spanish language and culture initiative in a doctor of pharmacy (PharmD) curriculum that would improve students' Spanish language skills and cultural competence so that graduates could provide competent pharmaceutical care to Spanish-speaking patients. DESIGN: Five elective courses were created and introduced to the curriculum including 2 medical Spanish courses; a medical Spanish service-learning course; a 2-week Spanish language and cultural immersion trip to Mexico; and an advanced practice pharmacy experience (APPE) at a medical care clinic serving a high percentage of Spanish-speaking patients. Advisors placed increased emphasis on encouraging pharmacy students to complete a major or minor in Spanish. ASSESSMENT: Enrollment in the Spanish language courses and the cultural immersion trip has been strong. Twenty-three students have completed the APPE at a Spanish-speaking clinic. Eleven percent of 2010 Butler University pharmacy graduates completed a major or minor in Spanish compared to approximately 1% in 2004 when the initiative began. CONCLUSION: A Spanish language and culture initiative started in 2004 has resulted in increased Spanish language and cultural competence among pharmacy students and recent graduates.

National estimates of enrollment in disease management programs in the United States: an analysis of the National Ambulatory Medical Care Survey data.

Disease management (DM) programs have demonstrated improvement in clinical and economic outcomes for patients with chronic conditions; however, the extent of utilization of these programs in the United States is not known. The rate of enrollment in DM programs was estimated using data from the National Ambulatory Medical Care Survey (NAMCS). Logistic regression analysis was used to identify predictors of enrollment in DM programs. The complex sampling design of the NAMCS was accounted in all analyses. The final study sample included 14,405 patient visits and indicated that only 21.3% of patients with at least 1 chronic condition utilize DM programs. Regression analysis demonstrated that patients who visit specialty physicians (excluding internal medicine) are more likely to be enrolled in a DM program than patients who visit general medicine/family practice physicians (P < 0.01). Patients with depression, diabetes, hyperlipidemia, or obesity were significantly more likely to be enrolled in a DM program than patients without these chronic conditions. Enrollment in a DM program was also affected by the total number of chronic conditions--patients with 2-4 chronic conditions were 1.29 times more likely to be enrolled in a DM program than patients with a single chronic condition (P = 0.026). In conclusion, although benefits of DM programs have been documented, their adoption rate remains extremely low. Additional studies are needed to identify other predictors and to tailor interventions to increase the adoption of such programs.

Dual-photoelastic-modulator-based polarimetric imaging concept for aerosol remote sensing.

A dual-photoelastic-modulator- (PEM-) based spectropolarimetric camera concept is presented as an approach for global aerosol monitoring from space. The most challenging performance objective is to measure degree of linear polarization (DOLP) with an uncertainty of less than 0.5% in multiple spectral bands, at moderately high spatial resolution, over a wide field of view, and for the duration of a multiyear mission. To achieve this, the tandem PEMs are operated as an electro-optic circular retardance modulator within a high-performance reflective imaging system. Operating the PEMs at slightly different resonant frequencies generates a beat signal that modulates the polarized component of the incident light at a much lower heterodyne frequency. The Stokes parameter ratio q = Q/I is obtained from measurements acquired from each pixel during a single frame, providing insensitivity to pixel responsivity drift and minimizing polarization artifacts that conventionally arise when this quantity is derived from differences in the signals from separate detectors. Similarly, u = U/I is obtained from a different pixel; q and u are then combined to form the DOLP. A detailed accuracy and tolerance analysis for this polarimeter is presented.