Cryogenically-cooled eyesafe laser diode arrays for resonant pumping of Er-doped gain media

Based on promising results obtained under Army Phase 1 SBIR funding, nLight proposes a Phase 2 continuation toward the development of high-power, cryogenically-cooled 1532-nm eyesafe laser diode arrays for use in resonant pumping of Er-doped gain media. Cryogenic cooling of diode lasers can provide great benefit to performance arising from the dramatic reduction in the threshold current and the increase in the diode’s slope efficiency. A penalty is paid in a large increase in the diode voltage, limiting the power conversion at cryogenic temperatures. During the Phase 1, nLight demonstrated a diode laser of novel epitaxy design (specifically targeting cryogenic operation) which greatly mitigated the voltage rise. The diode laser demonstrated >70% power conversion efficiency and was, to the best of our knowledge, the highest reported efficiency to date for an InP-based laser diode. During the proposed Phase 2 program, this approach will be optimized through a series of statistically designed and physically motivated development campaigns. Reliability and manufacturability will be designed in from the start. At the end of the program, high-power (>500W rated), high-efficiency (>75% rated) arrays of the 1532-nm prototype laser diodes will be delivered to the Army Research Laboratory for use in solid state pumping experiments.