Wideband lasers and receivers for lasercom applications

We summarize the design, development, and testing of laser and receiver modules necessary to support wideband direct detection intersatellite laser communications in the 780 nm-870 nm spectral region (referred to as the 830 nm). A 1250 Mbps hybrid receiver was fabricated in a 0.6" diameter 12-pin TO-8B package, and includes a silicon avalanche photodiode (APD), a GaAsFET preamp, and a silicon bipolar postamp. This unit is used in concert with a SONET compatible ASIC which performs the clock recovery and data decisions and retiming. Testing of this APD hybrid receiver at 1.25 Gbps demonstrated a sensitivity of 150 photons/bit at a 10^-6 bit error rate. We also report on the testing of 1-2 watt 860 nm MOPA lasers made by SDL, and the development of a compact communications transmitter module for this high power laser. When properly matched, these MOPA lasers demonstrate a 2-3 GHz bandwidth with 1 watt of usable diffraction limited output power. We have also designed a microlens collimator for the MOPA which has been fabricated, and have initiated work on a hybrid laser driver suitable for data rates up to 2-3 Gbps at the high drive current required for the full modulation depth of the laser. These efforts will allow the complete opto-electronic transmitter module and the receiver front-end module to each be housed in a package size as small as 1.5 cubic inches. The end goal of these efforts is to realize very compact, high performance laser and receiver modules that are compatible with an advanced monolithic glass block lasercom terminal concept