Abstract: A multiplexed optical fiber readout system is coupled to an array of scintillators, such as BGO crystals, for determining position and energy of radiation events in gamma ray imaging systems. Each scintillator in an N.times.M array is coupled to a pair of step-index-of-refraction, wavelength shifting, fluorescent fibers. The fluorescent fibers are arranged in N rows and M columns (or other indexed scheme) such that each scintillator is coupled to one row fiber and one column fiber, for example. The fluorescent fibers are coupled to clear optical fibers terminating at high quantum efficiency photon counters. Readout of the array of scintillators is accomplished by detecting coincident fluorescent photons in orthogonal pairs of the N+M fibers. By multiplexing the readout on row and column fibers, the number of signal channels is reduced by a factor of (N+M) / (N.times.M), which can greatly reduce cost or increase resolution compared with existing gamma ray imaging systems.

Abstract: A three dimensional positron emission tomography system is used in conjunction with a short lifetime positron emitter introduced into a test object to function as a tracer. A plurality of high density, high atomic number scintillating crystals are positioned within a cylindrical volume surrounding the test object, each such crystal being adapted to emit visible light in response to absorption of a gamma ray photon emitted when a positron from the tracer annihilates with an electron within the test object. A plurality of visible light photon counters is provided, with each such counter associated with one of the scintillating crystals such that the emission of visible light from the crystal is detected by the counter. Electronic circuitry sequentially polls the plurality of counters and compiles data indicative of the time at which a visible light photon was detected by each photon counter.

Abstract: An impurity band conduction (IBC) infrared detector is provided with a photoluminescent (PL) layer proximate the blocking layer of the device. The PL layer comprises a narrow band-gap semiconductor material selected for generating long wavelength infrared (LWIR) photoluminescent photons in response to incident photons of selected spectra. The PL layer improves the quantum efficiency of IBC devices in detecting incident photons in the short wavelength infrared (SWIR), ultraviolet (UV), and X-ray spectra. The thickness of the PL layer can be varied to optimize the photoluminescent response to incident photons of a selected spectrum. In a back-illuminated detector array, absorption of a SWIR photon in the PL layer results in one or more LWIR photons emitted in a time that is sufficiently shorter than the multiplexer frame time.

Abstract: Electromagnetic energy is detected by providing an extrinsic impurity-band semiconducting region with a first conductivity type impurity concentration high enough to create an impurity energy band. An intrinsic semiconducting blocking region is provided with first and second conductivity type impurity concentrations which are low enough that substantially no charge transport occurs by an impurity conduction mechanism. An electrical potential is applied to the impurity-band and blocking regions to create an electric field across the regions, then the regions are exposed to electromagnetic energy to generate intrinsic charge carriers in the regions. The electrical current induced in the regions as a result of the intrinsic charge carrier generation is measured.

Abstract: An edge illuminated impurity band conduction detector includes an extrinsic semiconducting IR-active layer with a first conductivity type impurity concentration high enough to create an impurity energy band. An intrinsic semiconducting blocking layer includes first and second conductivity type impurity concentration low enough that substantially no charge transport occurs by an impurity conduction mechanism. The IR-active and blocking layers are positioned between first and second contacts such that an electrical potential applied to the contacts creates an electric field across the layers. The detector is oriented such that the electromagnetic energy impinges on an edge of the IR-active layer and propagates in the IR-active layer in a direction substantially orthogonal to the applied electric field, the IR-active layer extending in the orthogonal direction for at least the absorption length of the electromagnetic energy.

Abstract: An edge illuminated optical detector array includes a series of two or more detectors which operate under an applied electric field. Each detector includes an extrinsic semiconducting active layer with a first conductivity type impurity concentration high enough to create an impurity energy band, and an intrinsic semiconducting blocking layer in which substantially no charge transport occurs by an impurity conduction mechanism. The detectors are positioned relative to one another such that optical energy incident on the array and directed substantially orthogonal to the applied electric field impinges on the first detector in the series and the portion of the optical energy which is transmitted by each detector is directed to the succeeding detector in the series. In this manner, the spectral content of the optical energy impinging on each detector is modified by the spectral transmission characteristics of the preceding detectors.

Abstract: A semiconductor diode is designed to operate at a temperature where the thermal generation of free charge carriers is negligible. The diode includes a first semiconducting layer with a sufficient concentration of first conductivity type impurities to exhibit metallic type conductivity, a second semiconducting layer with a sufficient first conductivity type concentration to create an impurity energy band and with a second conductivity type impurity concentration less than half the first, and a blocking layer between the first and second layers with a sufficiently low impurity concentration that substantially no charge transport can occur by an impurity conduction mechanism. First and second ohmic contacts are deposited on the first and second layers opposite the blocking layer. The same types of layers are used to construct transistors.

Abstract: A solid state photon detector includes a semiconducting blocking layer with sufficiently low donor and acceptor concentrations that substantially no charge transport can occur by an impurity conduction mechanism. A semiconducting buffered layer is provided with a sufficiently high donor impurity concentration to create an impurity energy band and with a sufficiently high acceptor impurity concentration that an electron cannot be injected into and drift through the layer without recombining with ionized donors. A semiconducting active layer is positioned between the blocking and buffered layers with a sufficiently high donor concentration to create an impurity energy band. The acitve layer also includes a sufficiently low acceptor impurity concentration that a photogenerated electron can drift through the active layer without recombining with ionized donors.

Abstract: Disclosed is a blocked-impurity-band detector, including an active layer which is doped with a sufficient amount of either a donor or an acceptor impurity that significant charge transport can occur in an impurity band in addition to the charge transport of electrons in the conduction band of the layer and of holes in the valence band of the layer. A blocking layer is disposed on the active layer and contains a sufficiently low concentration of impurities that significant charge transport cannot occur in the blocking layer except by means of electrons in the conduction band of the layer or holes in the valence band of the layer. First and second electrodes are provided for applying a bias potential across the active and blocking layers.