ULTRAHIGH SENSITIVITY SINGLE-PHOTON DETECTOR USING A SI AVALANCHE PHOTODIODE FOR THE MEASUREMENT OF ULTRAWEAK BIOCHEMILUMINESCENCE

A single-photon detector using a Si avalanche photodiode (APD) has been constructed. A trans-impedance type front-end circuit was employed in order to achieve a high signal-to-noise ratio. The APD and front-end circuit were cooled in liquid nitrogen to reduce dark count rate and circuit noise. The system performances were measured, and the achieved dark count rate and total quantum efficiency were 0.08 count/s and 5%, respectively. The sensitivity was evaluated to be of the order of 10-19 W. The APD single-photon detector was demonstrated to be available for measurement of the ultraweak biochemiluminescence at the order of 10-19 W/mm2 from brain slices, i.e., hippocampal slices. It was shown that the addition of tetrodotoxin to the hippocampal slice caused a decrease in the intensity of biochemiluminescence. © 1995 American Institute of Physics.