Fabrication of 3-D light concentrating microphotonic structures by anisotropic wet etching of silicon

Grant W. Bidney; Boya Jin; Lou Deguzman; Thomas C. Hutchens; Joshua M. Duran; Gamini Ariyawansa; Igor Anisimov; Nicholaos I. Limberopoulos; Augustine M. Urbas; Kenneth W. Allen; Sarath D. Gunapala; Vasily N. Astratov

doi:10.1117/12.2610426

5 March 2022 Fabrication of 3-D light concentrating microphotonic structures by anisotropic wet etching of silicon

Grant W. Bidney, Boya Jin, Lou Deguzman, Thomas C. Hutchens, Joshua M. Duran, Gamini Ariyawansa, Igor Anisimov, Nicholaos I. Limberopoulos, Augustine M. Urbas, Kenneth W. Allen, Sarath D. Gunapala, Vasily N. Astratov

Author Affiliations +

Proceedings Volume 12012, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XV; 120120B (2022) https://doi.org/10.1117/12.2610426
Event: SPIE OPTO, 2022, San Francisco, California, United States

Conference Poster

Abstract

Silicon has been commonly used in the microelectromechanical systems (MEMS) community for the past sixty years, and anisotropic wet etching with tetramethylammonium hydroxide (TMAH) has been central to these fabrication efforts. It has been shown anisotropic wet etching of silicon is an ideal method to rapidly fabricate components with huge production volume, and low cost. Although TMAH has been commonly used to create integrated circuits, the technology hasn’t been fully explored for optical applications. Four types of light concentrating arrays were fabricated with this technology in this work: (i) micropyramids with 54.7˚ sidewall angle, (ii) microcones with 45˚ sidewall angle, (iii) inverted square pyramids with 54.7˚ sidewall angle, and (iv) inverted triangular pyramids with different sidewall angles. The 54.7˚ sidewall angle arrays have smooth sidewalls due to etching with TMAH, which reduces scattering loss. The 3-D microphotonic structures were created through a comparable fabrication protocol, but require different photoresists, mask alignments, and if the surfactant Triton X-100 was utilized during the etch. The fabricated structures can be either heterogeneously integrated with front-illuminated focal plane arrays (FPAs) created in material systems with high quantum efficiency, or be monolithically integrated with metal/silicide Schottky barrier photodetectors for operation in short-wave infrared (SWIR) or mid-wave infrared (MWIR) regimes. The light concentrating capability of the proposed structures was tested by finite-difference time-domain modeling. Experimentally, the formation of photonic nanojets at the tips of micropyramids was demonstrated using illumination by a 2.96 μm wavelength Er:YAG laser.

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Grant W. Bidney, Boya Jin, Lou Deguzman, Thomas C. Hutchens, Joshua M. Duran, Gamini Ariyawansa, Igor Anisimov, Nicholaos I. Limberopoulos, Augustine M. Urbas, Kenneth W. Allen, Sarath D. Gunapala, and Vasily N. Astratov "Fabrication of 3-D light concentrating microphotonic structures by anisotropic wet etching of silicon", Proc. SPIE 12012, Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XV, 120120B (5 March 2022); https://doi.org/10.1117/12.2610426

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