Method for obtaining linear spectral responsivity of InGaAs-photodetector in the NIR wavelength range

A simple linear interpolation of the spectral responsivity of a special type detector has been obtained in the range from 960 nm to 1550 nm. The detector consisted of three InGaAs-based photodiodes arranged in reflection trap detector mode. In such a detector, the photodiodes are mounted in a configuration where the non-absorbed reflected light from the first photodiode is directed to the subsequent photodiode having totally five reflections in the detector. As a result, the overall reflectance of the trap detector is smaller than that of a single photodiode improving responsivity performance significantly. The trap detector was calibrated in the wavelength range from 840 nm to 1700 nm. We found that in the near infrared (NIR) spectral range from 960 nm to 1550 nm the responsivity of our trap detector is almost linear function of on the wavelength: the deviation of measured responsivity values from fitted line was within ±0.8 %.