Eye-safe fiber-coupled laser pumps for high power

Erbium-doped solid state and fiber lasers provide an attractive source at eyesafe wavelengths, and the potential for ultra-low quantum defect pumping by diode lasers operating around 1532-nm. Unfortunately, these systems, to date, have been limited by the spatial brightness of the diode pumps. Under the proposed Phase 1 program, nLight will design, fabricate, test, and deliver to the Army (or a recipient of their choosing) a >30W (rated) compact, conductively-cooled diode laser pump module, coupled to a 100 µm core, 0.15 NA fiber. The module is based on nLight’s Pearl platform, which has recently been leveraged to deliver record brightness in the 9xx-nm wavelength regime. This proposal seeks to extend the technique to the eyesafe wavelengths. The unit will emit at 1532.2 nm with a predicted electrical-to-optical efficiency (measured at the fiber output) of 27%. As an option to the program, nLight will design and deliver to the Army (or a recipient of their choosing) a similar-performing unit which is wavelength locked (spectral width < 0.5nm FWHM) by means of a volumetric Bragg grating. The module will include an integrated heater on the grating element to allow wavelength tunability in the range of +/- 0.2 nm.