Linearity improvement in a high dark-current short-wave infrared array spectrometer

Abstract

Spectrometers that include extended-range linear InGaAs arrays make it possible to measure optical signals to 2500 nm. Available arrays, however, have more than 100 times the dark current as that of conventional arrays, which are limited to 1700 nm. This behavior leads to non-linearity in a short-wave infrared spectroradiometer used to monitor spectral radiance of an integrating sphere uniform source. A method of improving linearity in an extended-range InGaAs array is presented. The non-linearity is corrected using a multi-point calibration at a number of lamp power levels whereby the calibration factor for each wavelength point depends on the lamp power in the integrating sphere. An algorithm in the spectroradiometer software chooses the correct calibration factors and reports the system spectral radiance values accordingly. This method reduced error by more than a factor of two.