On-chip Integration of Metasurface-Based Beam Splitter with Variable Split Ratio

The development of optical systems is moving toward multifunctionality and miniaturization. Conventional beam splitters, constructed with prisms or flat glass plates, are bulky and limit optical system design. Metasurfaces are artificial planar optical elements whose flatness and compactness facilitate optoelectronic integration with semiconductor devices, resulting in the development of miniaturized and multifunctional optoelectronic devices. Here, multifunctional beam splitters are proposed that monolithically integrate metasurfaces with a standard vertical cavity surface-emitting lasers (VCSELs). By engineering the phase profile, the device can achieve various beam-splitting functions, including a polarization-insensitive high-efficiency power splitter, a multi-channel power splitter, and a polarization power splitter. Experimental results show that the measured splitting ratios (SRs) of the polarization-insensitive power splitters are as follows: 0^th to -1^st order ranges from 0.92 to 70, and -1^st to -2^nd order ranges from 0.01 to 80. The multi-channel power splitter exhibits SR of 6.6:4:3:1 for the -1^st and +1^st orders in the x and y directions. The polarization power splitters enable tunable SRs for ±1 orders, ranging from 0.06 to 1.1. This on-chip integration of power beam splitter is believed has promising potential to drive the development of new compact optical systems and advance integrated photonic applications.