Influence of Beam Profile and Fiber‐to‐Device Separation on Segmented GaAs Photovoltaic Power Converters

Segmented photovoltaic (PV) devices used in power‐over‐fiber systems are sensitive to spatially nonuniform illumination, which affects carrier generation and device performance. This study evaluates the influence of beam profile and working distance on a four‐segment, 350 µm‐diameter GaAs‐based PV cell under quasi‐Gaussian and annular illumination profiles delivered through a double‐clad fiber. Beam propagation is governed by the effective numerical aperture and launch conditions, resulting in different divergence characteristics for each profile. The fiber‐to‐device separation is varied up to 2 mm to identify optimal operating conditions. A peak power conversion efficiency of 50% is obtained under quasi‐Gaussian illumination at an illumination density of 10.7 W/cm 2 and a working distance of 1 mm. Under annular illumination, an efficiency of 47% is achieved at a higher illumination density at a separation of 0.4 mm, with a corresponding fill factor of 81%. The annular beam concentrates optical power near the device periphery, reducing interaction with isolation trenches and improving the uniformity of carrier collection across segments. A maximum open‐circuit voltage of 4.81 V is measured under annular illumination at an illumination density of 62.6 W/cm 2 . These results indicate that beam profile–dependent divergence and working distance determine the optimal illumination conditions for segmented PV devices.