Description: There is demand for vastly improved deep space satellite communications links. As data rates dramatically increase due to new sensor technologies and the desire to pack even more sensors on spacecraft, it is imperative that new solutions be compact in size, light in weight, be high speed, and highly power efficient. NASA has recognized optical links offer potential improvements in power and in size due to a substantially narrower beam and smaller components. An ideal technology for such links is a laser transmitter master oscillator power amplifier (MOPA) using pulse position modulation techniques. In Phase I, a design was developed for a laser transmitter MOPA with a wall-plug efficiency of up to 23% operating at 1560nm. Operating at longer wavelength offers a number of advantages including the use of numerous off-the-shelf components. This Phase II proposal will demonstrate a working prototype of the design at a Technology Readiness Level 4 by the end of the program.

Benefits: Fast rise time MOPA structures for optical communications can serve as ideal input sources for eye safe pulsed fiber laser based sources for material processing and other scientific applications. The flexible beam path and distributed thermal dissipation make fiber lasers ideal for many applications, especially CW ones, and for this reason fiber lasers have made significant inroads into many CW based laser markets such as material processing and long pulse laser marking. Pulsed fiber lasers have not been successful in penetrating laser markets due the adverse effects of fiber non-linearities on pulse width, and non-linear optical generation efficiency. At peak powers in the 100's of kW, nonlinear optical effects play a destructive role in widening pulses and lowering peak powers. A well designed MOPA structure can alleviate many of these problems. The narrow pulse width and fast rise times of the MOPA system create opportunities for temporal pulse shaping and multi-pulse operation. These techniques have already proven themselves successful in semiconductor memory repair and high speed resistor trimming. Eye-safe operation is crucial in many commercial and industrial settings in order to reduce the cost of additional containment enclosures.

High power fiber master oscillator power amplifier (MOPA) transmitters provide the basis of high speed deep space communications links using pulse position modulation. NASA has planned for such devices to be used in future spacecraft. Previous work has demonstrated laser transmitter MOPAs up to 100 MHz with wall plug efficiencies up to 18% and operating at 1064nm which requires bulky optical components. The techniques developed in this proposal will provide improvements in efficiency, data rate, size, and weight compared to designs already investigated by NASA.