Abstract

Development of techniques and systems for ultraweak light detection in the near-IR region ranging from 1 to 2 μm is very attractive and useful not only for optical communications and optical data processing but also for other applications such as spectroscopy, life sciences, and biotechnology. We report some experimental results of the basic operational characteristics in a IR photon counting scheme for a planar InGaAs avalanche photodiode (APD), which is primarily developed for high-speed optical fiber communications. The APDs used in the experiment are FPD13U81WS (Fujitsu) of which the operative diameter is 80 μm. This APD was cooled to a temperature of 77 K to effectively reduce dark pulses below ~1000 counts/s. Then the APD was dc biased to 99% of breakdown voltage (V_b = 47.20 V at 77 K). Pulse-height distributions of both the dark and signal pulses were analyzed by changing various operational conditions. Based on the measurement results we obtained, some evaluations were also made of the SNR, a quality factor, and the excess noise multiplication factor for this APD. The minimum detectable optical power was estimated to be ~1 × 10⁻¹⁴ W with an averaging time of 100 s. The linearity of the count rate for signal pulses for this device was maintained between nearly 1 × 10⁻¹¹ and 1 × 10⁻¹⁴ W.

© 1988 Optical Society of America