Imaging in the Short-Wave Infra-Red (SWIR) has some advantages over imaging in the visible spectrum or over thermal imaging in the MWIR or LWIR. InGaAs/InP technology with a cut-off wavelength of 1.7 μm allows for two-dimensional (2D) detector arrays with high electro-optical performance at room temperature. For optimal performance, such detectors can be moderately cooled and temperature stabilized using a Thermo-Electric Cooler (TEC). This results in a small package with low power consumption, and relatively low production costs.
SCD's "Cardinal 640" detector consists of a 640×512/15μm InGaAs array which is coupled to the multi-function SNIR Read-Out Integrated Circuit (ROIC) using Flip-chip bonding. The ROIC has a "high gain" mode with a low readout noise of ~40e- (including Correlated Double Sampling), specifically designed for typical SWIR signals. The SNIR ROIC also implements several functionalities in each pixel, which traditionally have been implemented at the system level, such as Asynchronous Laser Pulse Detection (ALPD) and 2D Laser Range Finding (TLRF). The Focal Plane Array (FPA) is integrated into a metallic package and is assembled with a low power proximity electronics board, which controls the ROIC and the TEC, and delivers Camera Link output to the system. The overall power dissipation is 1.5W, not including TEC cooling which is required in some applications. In this work we report on the electro-optical characteristics of the "Cardinal 640" detector. The performance figures are based on measured results from over 150 detectors manufactured by SCD over the last year. The dark current density is typically below 1.5 nA/cm2 at 280K, the Quantum Efficiency is higher than 80% at 1.55 μm, and the operability is higher than 99.5%.
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