Development and characterisation of laser power converters for optical power transfer applications

Interest in single-junction photovoltaic devices has been renewed in recent years due to their potential to produce very high optical to electrical conversion efficiencies under monochromatic illumination. A single-junction photovoltaic converter was developed for monochromatic radiation (a laser power converter (LPC)) to specifically convert monochromatic light at a wavelength of 1.55 µm (which is eye and skin safe up to a power density of 1 kW/m2) into electrical energy. Such devices find use in space-based laser power transfer, as well as fibre optic power delivery and the remote powering of subcutaneous equipment and other electrical devices. The LPC design is based on lattice-matched InGaAsP/InP, which includes elements for photon recycling and efficient carrier extraction. Here, the design process is reported based on computer simulated characteristics, and compare them to experimental data from both laboratory and field tests. The LPC demonstrates a conversion efficiency of 45% ± 1% under illumination at 1.55 µm and 1 kW/m2, and a conversion efficiency of 13.3% under AM1.5 solar illumination for potential dual-use applications. With further design optimisation, it has been predicted that the conversion efficiency will exceed 50% at 1.55 µm and 1 kW/m2.