Scientific Reports (Mar 2021)

Inverse design of photonic meta-structure for beam collimation in on-chip sensing

  • Robin Singh,
  • Yuqi Nie,
  • Mingye Gao,
  • Anuradha Murthy Agarwal,
  • Brian W. Anthony

DOI
https://doi.org/10.1038/s41598-021-84841-2
Journal volume & issue
Vol. 11, no. 1
pp. 1 – 11

Abstract

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Abstract Designed or patterned structured surfaces, metasurfaces, enable the miniaturization of complex arrangements of optical elements on a plane. Most of the existing literature focuses on miniaturizing the optical detection; little attention is directed to on-chip optical excitation. In this work, we design a metasurface to create a planar integrated photonic source beam collimator for use in on-chip optofluidic sensing applications. We use an iterative inverse design approach in order to optimize the metasurface to achieve a target performance using gradient descent method. We then fabricate beam collimators and experimentally compare performance characteristics with conventional uniform binary grating-based photonic beam diffractors. The optimal design enhances the illumination power by a factor of 5. The reinforced beam is more uniform with 3 dB beam spot increased almost ~ 3 times for the same device footprint area. The design approach will be useful in on-chip applications of fluorescence imaging, Raman, and IR spectroscopy and will enable better multiplexing of light sources for high throughput biosensing.