SPLTRAK Abstract Submission
High-Performance O-Band Photonic Power Converters Under Non-Uniform Laser Illumination
Meghan N. Beattie1, Henning Helmers2, Gavin P. Forcade1, Christopher E. Valdivia1, David Lackner2, Oliver Höhn2, Karin Hinzer1
1SUNLAB, Centre for Research in Photonics, University of Ottawa, Ottawa, ON, Canada
/2Fraunhofer Institute for Solar Energy Systems ISE, Freiburg, Germany

Photonic power converters designed and fabricated at Fraunhofer ISE for operation in the O-band were measured under non-uniform 1319 nm laser illumination with five spot sizes. Two 5.4 mm2 devices were studied. The first used lattice-matched InGaAsP on an InP substrate while the second used lattice-mismatched InGaAs grown on GaAs with a step-graded metamorphic buffer.
The maximum measured efficiencies were 52.9% at a laser power of 353 mW and 48.8% at 413 mW for the lattice-matched and -mismatched designs respectively. Both maximal efficiencies were measured with a spot size of 2.3 mm, the largest and most uniform laser-spot applied in this study. The devices were insensitive to the illumination uniformity for input powers < 100 mW, exhibiting a logarithmic relationship between open-circuit voltage and short-circuit current density consistent with the non-ideal diode equation. At higher powers, deviations were observed from this trend and both devices exhibited better performance for larger spot sizes.
Distributed circuit modeling (DCM), which uses a two-diode model and accounts for lateral current flow and resistive losses, was used to explore the mechanisms responsible for the measured beam-size dependence. Agreement was achieved between the DCM and experimental data measured under broadband uniform illumination. Under a Gaussian laser-illumination profile, comparison between the DCM and experimental data suggested that both resistive losses and localized heating likely contributed to the performance reductions under non-uniform illumination. Better performance at higher illumination powers could be achieved by engineering a more uniform illumination profile, optimizing the front metallization, or adopting multi-junction device architectures.