Dual charge integrating amplifier circuit using two GaInAs-InP pin photodiodes for ultraweak light detection in the near infrared region

A novel detection system based on a dual charge integrating amplifier (dual-CIA) circuit that employs two GaInAs-InP pin photodiodes, has been developed for the detection of the ultraweak, near-infrared light generated by chemical and biochemical reactions. The minimum detectable power was measured to be as low as 0.9/spl times/10/sup -15/ W. Using this system, we were able to detect the ultraweak light (around 1268 nm), emitted from singlet oxygen molecules during the chemical reaction between OCl/sup -/ and H/sub 2/O/sub 2/, for a given H/sub 2/O/sub 2/ concentration that is far lower than those reported previously.