Imaging of visible photons using hybrid silicon pixel detectors

A novel type of visible-photon pixel detector, which combines the usually conflicting features of fine spatial resolution and high readout rate, is being investigated. For this purpose, a modified, high-resistivity silicon detector has been bump-bonded to a CMOS readout chip and the device has been illuminated with various pulsed monochromatic light sources. The device has 1006 active elements with a short dimension of 75 μm, and can be read out at a clock frequency of 5 MHz. Although the structure was not optimized for photon detection, it was possible to measure almost the same quantum efficiency as a commercial silicon photodiode for short wavelengths and a better one in the near infrared. These photopixels could be used for high-speed, two-dimensional photon imaging and could replace, after image intensification, CCDs or multi-anode PMTs.