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We summarize a compact lasercom terminal implementation based on a previously described system concept, and report on measurements made on a prototype optical system built on internal MITRE funds. This paper discusses the fabrication and test of an innovative hardware proof-of-concept for an advanced satellite lasercom terminal with a ten-fold size, weight, and production cost reduction over current practice. We have built and tested a proof-of-concept of the optics portion of a full duplex `monolithic glass block' (MGB) lasercom terminal. The complete MGB optical system is only 6' X 4' X 0.5' and weighs less than a pound. A complete terminal which includes a 3 - 4 inch telescope and gimbal could be implemented for as little as 15 - 30 pounds. The optical system test results are reported. Our approach uses emerging technologies and a highly integrated system design, based on representative system requirements for satellite crosslinks. Technology evaluation and system trades led to a novel optics design for a lasercom terminal, based on thin film coatings and half-inch glass cubes. The emerging photonic technologies employed include liquid crystals for solid state switching, automatic gain control, and microradian alignment; multi-layer dielectric films for optical bandpass filters, dichroic separation, and polarization control; semiconductor lasers with microlens optics; and an original design where all the optics are realized in planar thin films incorporated on small glass substrates, nominally one-half inch in size. These glass cubes are permanently bonded together to form a monolithic ensemble. Hence, we have coined this implementation the monolithic glass block (MGB) approach. Fused silica is used throughout for reasons of superb radiation resistance and thermal stability. The thin film filters, switches, and polarizers perform all the necessary functions in collimated light. This approach is feasible because the optical paths have been dramatically reduced to eliminate the need for relay optics, and the design has been refined such that the entire optical assembly is implemented with a single lens for each laser transmitter for beamforming, and a single lens for each receiver for imaging. The collimated optics design and MGB approach results in greatly relaxed fabrication, alignment, and assembly requirements, which are dominant schedule and cost drivers in the implementation of current lasercom terminal designs.
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