Highly-Reliable, Radiation-Hard Laser Diode Active Materials

ABSTRACT: Quantum-dot gain medium in semiconductor lasers exhibit higher resistance to radiation induced damage. Irradiated diode lasers comprising quantum-dot gain medium demonstrated lasing two orders of magnitude beyond the maximum dose sustainable by quantum-well semiconductor lasers. These studies point to the strong potential for achieving a radiation resistant diode laser. Additionally, theoretical predictions anticipate the ideal quantum dots will possess many useful properties including ultra-low threshold current density, high optical gain, low linewidth enhancement factors, and temperature insensitive device performance, based on the delta-function idealized density of states. In addition, there is potential to have threshold current densities, Jth, and external differential quantum efficiencies which are less temperature sensitive (i.e. high To and T1 ) than QW lasers. Both of these factors are important for achieving high CW output power and high CW total power conversion efficiency in diode lasers beyond what has been achieved in the Super High Efficiency Diode Sources program. We propose to design a quantum-dot active laser comprising an optimized heterostructure for an emission wavelength of 980 nm in order to obtain output powers in excess of 10 watt with power conversion efficiency greater than 60% and demonstrate high reliability and high resistance to radiation damage. BENEFIT: Quantum-dot semiconductor laser at 0.98 micron emission wavelength will enable use of lightweight and efficient laser for numerous applications in high radiation environment such as space.