Optical Photon Detectors Research Articles

(PS) 2: a new semiconductor device for positron-sensitive picosecond detection of single optical photons

A position-sensitive photodiode of new concept is introduced. The device is operated biased above the breakdown voltage in the so-called Geiger mode. The absorption of a single photon results in a mA-range avalanche pulse. The time and position (one coordinate) information of the photon arrival are carried by the avalanche current leading edge. The physics of the device operation is discussed: constraints in the device design are derived. Experimental measurements on silicon test structures with a position-sensitive area of 70 by 14 μm 2 are presented. Spatial resolution better than 10 μm FWHM (full width at half maximum), limited by the spot size of the light beam, and temporal resolution better than 100 ps FWHM are demonstrated.

Two-dimensional photon counter for x-ray imaging

This paper characterizes an imaging x-ray detector formed by coupling a gadolinium oxysulphide phosphor to the input of an optical imaging photon detector. The device is small, light, easy to use, and features a direct digital readout. It exhibits fairly high efficiency (40%–80%) and high resolution (160 μm-width point spread function) near the center of its 40-mm active area. There is a small amount of pincushion distortion which seems to be associated with a loss in resolution toward the edge of the active area. The device has very low noise and can be used at x-ray fluxes down to about 0.1 x-ray/mm2/s without loss of accuracy but it is count rate limited at 105 x rays/s over the active area and so is not usable in high-flux situations such as are often found at synchrotrons. We have used the device to record good diffraction patterns from striated rabbit muscle in 30 min on a rotating anode x-ray generator: less than one tenth the time needed under similar conditions when using film.