Ultrahigh-sensitivity infrared detection system using an InGaAs p-i-n photodiode with low dielectric polarization noise

We developed a highly sensitive infrared photodetection system using an InGaAs p-i-n photodiode. The temperature and data sampling rate dependences of the readout noise were measured to determine the optimum temperature for low-noise detection. The optimum temperature for sampling rates below 100 Hz was 100 K, and the readout noise at 1 Hz was 2.5 e. The readout noise at 1 MHz and 140 K was 49.4 e. The light detection limit of the system was 8.2×10(-19) W at a wavelength of 1.3 μm. The spectral noise densities of a readout circuit were measured in order to determine the origin of noise.