Fabrication of GaN monolithic doubly-resonant microcavity SHG device on Si trapezoidal structure (Conference Presentation)

Tomoaki Nambu; Tenta Komatsu; Keishi Shiomi; Yasufumi Fujiwara; Masahiro Uemukai; Ryuji Katayama

doi:10.1117/12.2507606

13 March 2019 Fabrication of GaN monolithic doubly-resonant microcavity SHG device on Si trapezoidal structure (Conference Presentation)

Tomoaki Nambu, Tenta Komatsu, Keishi Shiomi, Yasufumi Fujiwara, Masahiro Uemukai, Ryuji Katayama

Author Affiliations +

Proceedings Volume 10918, Gallium Nitride Materials and Devices XIV; 109180G (2019) https://doi.org/10.1117/12.2507606
Event: SPIE OPTO, 2019, San Francisco, California, United States

Abstract

Nitride semiconductors with large optical nonlinearity and high optical damage tolerance have potential for high-efficiency wavelength conversion. However, it is difficult to form the quasi-phase matched (QPM) periodic polarity-inverted structure, and a long interaction length of the order of cm is usually required for achieving high SHG efficiency in QPM devices. Then we propose a GaN monolithic microcavity SHG device with high-reflectivity Bragg reflectors located on both sides of the GaN resonator to enhance the excitation light intensity within the resonator significantly. By appropriate phase control at reflection, phase mismatch can be compensated even in the absence of the polarity-inverted structure. Due to a very short cavity length of ~ 10 μm, it is necessary to secure a laser beam path by etching the substrate outside of the cavity. In this work, the monolithic microcavity on the Si trapezoidal structure was fabricated using a thick GaN film on a Si substrate. The Cr/Ni masks with microcavity pattern were formed by EB drawing, EB evaporation and lift-off process. After the dry etching by ICP-RIE using Cl2 gas, KOH wet etching was performed in order to improve the sidewall verticality and flatness. The structure was covered by a Ni mask again. After removing the remaining GaN film and the underlying buffer layer, the Si substrate outside of the microcavity was deeply etched by ICP-RIE using SF6 gas. Finally, the Ni mask was removed by wet etching. We will report on the optical characteristics of the fabricated device in the presentation.

Conference Presentation

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Tomoaki Nambu, Tenta Komatsu, Keishi Shiomi, Yasufumi Fujiwara, Masahiro Uemukai, and Ryuji Katayama "Fabrication of GaN monolithic doubly-resonant microcavity SHG device on Si trapezoidal structure (Conference Presentation)", Proc. SPIE 10918, Gallium Nitride Materials and Devices XIV, 109180G (13 March 2019); https://doi.org/10.1117/12.2507606

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KEYWORDS

Gallium nitride

Optical microcavities

Silicon

Second-harmonic generation

Photomasks

Nickel

Resonators

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