Eye-Safe 1.5 and 2.0 Micron Laser Power Conversion Using Metamorphic InGaAs Photovoltaic Devices
Laser power transmission at 1.5 and 2.0 microns are considered eye-safe up to 0.1 W/cm2 irradiance. Further, the atmospheric bands at these two wavelengths may provide the highest optical transmission through the atmosphere in hazy conditions. By slowly changing the lattice-constant of InGaAs with a Compositionally Graded Buffer (CGB), we have fabricated InGaAs photovoltaic (PV) devices over a wide range of bandgaps useful for multijunction concentrating photovoltaic devices, thermophotovoltaic devices, and Laser Power Converters (LPC). Here, we have demonstrated monochromatic power conversion of 1.5-micron light with an eye-safe efficiency of 39.8% at 0.1 W/cm2 with InGaAs devices lattice-matched to InP with an Antireflection Coating (ARC). We have also demonstrated 30.2% and 24.5% eye-safe LPC efficiency of metamorphic InGaAs devices grown on GaAs substrates using GaInP and AlGaAsP CGBs, respectively. Finally, we have demonstrated metamorphic InGaAs devices grown on InP and GaAs substrates that are estimated to have eye-safe LPC efficiencies at 2.0 microns of 27.4% and 20.9% respectively. The efficiencies of all these LPC devices continues to increase up to about 30-70 times the eye-safe irradiance.