High-energy laser designed to operate in space

A diode-pumped, 15-mJ solid-state laser intended for space-based altimetry and ranging has been designed for NASA`s Goddard Space Flight Center (Greenbelt, MD) by Lightwave Electronics Corp. (Mountain View, CA) under a two-year Phase II Small Business Innovation Research (SBIR) contract. The first prototype of the laser was recently shipped to NASA for evaluation and testing, according to Dave Shannon, principal investigator on the project at Lightwave.

High-energy laser designed to operate in space

Stephen G. Anderson

A diode-pumped, 15-mJ solid-state laser intended for space-based altimetry and ranging has been designed for NASA`s Goddard Space Flight Center (Greenbelt, MD) by Lightwave Electronics Corp. (Mountain View, CA) under a two-year Phase II Small Business Innovation Research (SBIR) contract. The first prototype of the laser was recently shipped to NASA for evaluation and testing, according to Dave Shannon, principal investigator on the project at Lightwave.

Several aspects of the laser design are unusual because of its intended operating environment. Space-based equipment needs to be rugged, lightweight, and reliable, explains project engineer Jason Detering; power consumption and heat dissipation also must be minimized. Thus, the heat loading of the laser head, for example, has been reduced by locating the pump-laser diodes in the power supply and fiber-coupling them to the laser head.

Oscillator/amplifier arrangement

In addition, the laser is based on an oscillator/amplifier arrangement, which reduces the mass of the head and makes it more shock resistant. An acousto-optic Q-switch is used because high voltage is not required, and it is rugged and reliable. In the power supply, which operates from 28 V dc, pulsed RF amplification reduces power consumption and passive cooling--the supply is designed to sit on an external cold plate--eliminating the need for a water supply to the system.

Two six-bar quasi-CW diode stacks that are polarization-coupled into ten optical fibers provide the laser pum¥energy. In the laser head, two of the fibers end-pum¥the solid-state Nd:YAG laser resonator while the other eight fibers pum¥the optical amplifier (see figure). The overall fiber-coupling efficiency to the laser head is about 67%. The laser produces diffraction-limited (M2 < 1.3), 15-mJ TEM00 output pulses at 1064 nm with a pulsewidth of 10 ns and pulse-repetition rate of 100 Hz. Comments Shannon, "These specifications and the laser`s unusual package design will enable it to operate on an orbiting platform as part of a system that might provide, for example, topographical mapping of large areas."

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