A low-noise detection system using an InGaAs PIN photodiode for near-infrared spectroscopic measurement has been developed. The InGaAs PIN photodiode is more suitable than a Ge PIN photodiode for detecting low-level light in terms of dark current and quantum efficiency. The detection system consists of an InGaAs PIN photodiode with a charge integrating amplifier (InGaAs-CIA) operated at 77 K. A minimum detectable power of 10−16 W was achieved at a wavelength of 1.28 μm.
