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High sensitivity deep ultraviolet (DUV) photodetectors operating at wavelengths shorter than 280 nm are useful for various applications, including chemical and biological identification, optical wireless communications, and UV sensing systems (1). While semiconductor avalanche photodiodes (APDs) can be more compact, lower cost and more rugged than the commonly used photomultiplier tubes (PMTs), commercially...
A new low-power application-specific integrated circuit (ASIC) for Cadmium Zinc Telluride (CZT) detectors for single-photon emission computed tomography (SPECT) application is being developed at BNL. As the first step, a 32-channel prototype ASIC was designed and tested recently. Each channel has a preamplifier followed by CR-RC3 shaping circuits and three independent energy bins with comparators...
We present a class of fibers that exploit light propagation in higher-order modes, and hence decouple the dispersion-versus-mode-area trade-off encountered in conventional fibers. This enables exploiting the multitude of nonlinear optical effects afforded by fibers, at energy levels potentially approaching those of tunable solid-state lasers.
Ge is an indirect bandgap material for research interest with possible photonic applications. In previous work, only direct bandgap emission was observed in the epitaxial Ge on Si, but both direct and indirect emissions were observed in the bulk Ge substrates. This discrepancy between epitaxial Ge and Ge substrate may be due to reabsorption of direct emission. In this work, the reabsorption is systematically...
Tunable random laser emission over a 7-nm waveband is demonstrated using a green-emitting π-conjugated polymer infiltrated into a photonic glass formed by micron- and submicron-size monodisperse silica spheres. Corresponding scattering cross-section, scattering length and transport mean free paths are calculated using the Mie scattering theory and, along with experimental results, indicate that this...
It has been shown recently that the classical phenomenon of optical activity, which is traditionally associated with chirality (helicity) of organic molecules, proteins and inorganic structures, can be observed in artificial planar media which exhibit neither 3D nor 2D chirality and called this effect "extrinsic chirality". This paper investigates a photonic metamaterial consisting of a...
We give an overview of recent results on slow and fast light in active semiconductor waveguides. The cases of coherent population oscillations as well as electromagnetically induced transparency are covered, emphasizing the physics and fundamental limitations.
In this work we show how the dispersion relation of slab-type PhCs can be directly determined both in the radiative and guided mode regimes by means of k-space spectroscopy. Angle-resolved reflectance, attenuated total reflectance and micro-photoluminescence spectroscopy are used to determine several important characteristics like band-edge dispersion, slow-light propagation or far-field intensity...
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