Development of low-noise and high-speed SWIR photo receivers

Abstract

There is strong interest in developing Short Wavelength Infrared (SWIR) photo receivers for applications like laser ranging and robotic vision. Recently, Spectrolab has developed a first generation low noise receiver for NASA. The receiver shows a bandwidth of 180 MHz, presently limited by the transimpedance amplifier (TIA). The first generation photoreceiver has InP avalanche photodiode (APD). The overall photoreceiver noise equivalent power (NEP) is less than 300 fW/√Hz. Furthermore, Spectrolab is developing low excess noise APDs with Impact Ionization Engineering (I2E). The I2E low noise APDs were built from baseline InAlAs APDs with a keff value of 0.22. A thin layer of InGaAlAs alloy was incorporated into the InAlAs multiplication layer in these devices. All the I2E APDs show lower keff-value than InAlAs and very low dark currents. Values as low as keff<0.1 have been demonstrated. These I2E APDs will be used in Spectrolab's second generation photoreceiver. A Noise Equivalent Power (NEP) of 300 fW/√Hz is expected over a 1GHz response bandwidth.