A 400 KHz line rate 2048 pixel modular SWIR linear array for earth observation applications

In this paper, we report about a family of linear imaging FPAs sensitive in the [0.9-1.7um] band, developed for high speed applications such as LIDAR, wavelength references and OCT analyzers and also for earth observation applications. Fast linear FPAs can also be used in a wide variety of terrestrial applications, including high speed sorting, electro-and photo-luminesce and medical applications. The arrays are based on a modular ROIC design concept: modules of 512 pixels are stitched during fabrication to achieve 512, 1024 and 2048 pixel arrays. In principle, this concept can be extended to any multiple of 512 pixels, the limiting factor being the pixel yield of long InGaAs arrays and the CTE differences in the hybrid setup. Each 512-pixel module has its own on-chip digital sequencer, analog readout chain and 4 output buffers. This modular concept enables a long-linear array to run at a high line rate of 400 KHz irrespective of the array length, which limits the line rate in a traditional linear array. The pixel has a pitch of 12.5um. The detector frontend is based on CTIA (Capacitor Trans-impedance Amplifier), having 5 selectable integration capacitors giving full well from 62x10³e-(gain0) to 40x10⁶e-(gain4). An auto-zero circuit limits the detector bias non-uniformity to 5-10mV across broad intensity levels, limiting the input referred dark signal noise to 20e-_rms for Tint=3ms at room temperature. An on-chip CDS that follows the CTIA facilitates removal of Reset/KTC noise, CTIA offsets and most of the 1/f noise. The measured noise of the ROIC is 35e-_rms in gain0. At a master clock rate of 60MHz and a minimum integration time of 1.4us, the FPAs reach the highest line rate of 400 KHz.