Ultra-High Efficiency Diffraction-Limited MOPA Diodes for Direct Diode High Power Lasers

For many important military tasks, such as the defense of surface ships against saturation attacks by swarms of drones or cruise missiles, expendable munitions are ineffective because they can be easily and cheaply overwhelmed, and the only realistic solution is provided by electrically powered laser weapons which offer a “deep magazine” and the ability to rapidly engage a multiplicity of widely divergent targets. Existing directed energy lasers are based on fiber-laser technology, which has many attractive characteristics but suffers from poor electrical-to-optical conversion efficiency because the conversion involves two cascaded steps: conversion of electricity to pump photons, and subsequent conversion of pump photons to the laser photon. Each of these steps involves loss of power and generation of waste heat. This has serious system implications in that much larger power sources and waste heat radiators are required than would theoretically be necessary. Diode lasers which convert electricity directly to the final output beam can cut the waste heat load by more than a factor of two compared to fiber lasers, but standard diode lasers have beam optical qualities that are too poor to be used directly in weapons, and both their spectral and beam qualities are incompatible with the beam combining technologies that are needed to obtain militarily required output powers. We are developing high power diode lasers based on monolithic master oscillator power amplifier (MOPA) designs that generate narrow line single-frequency beams with diffraction-limited beam and powers in the tens of Watts. These performance levels are orders of magnitude better than conventional diode designs. These diode designs are compatible with both coherent and incoherent beam combining technologies, and are highly manufacturable at low cost using conventional fabrication technologies. Approved for Public Release | 22-MDA-11102 (22 Mar 22)