Spectral beam combining of diode laser bars achieve efficient near diffraction limited output power

Abstract

The use of diode laser bars has traditionally been limited in many applications because of their poor beam quality in the plane of the junction (slow direction). Spectral Beam Combination (SBC) corrects this defect with minimal impact on efficiency. Aculight has demonstrated efficient SBC of nearly 400 single transverse mode semiconductor lasers. The semiconductor lasers were packaged in two adjacent 1-cm wide, 200 emitter bars. The M 2 of a single 1-cm wide diode bar is typically greater than 1000. Using SBC we have measured an output M 2 of less than 1.5. The output bandwidth of the device is ~10 nm; and it is this spectral width that allows combination with the result that each of the 200 lasers deliver power through the same output aperture. The efficiency of this process was measured at >70% when high quality optical components were employed. Efficiency is defined as the SBC output power normalized to the power provided by the diode bars without SBC. With single emitters we have achieved SBC efficiencies of >80%.