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Enhanced Second Harmonic Generation from vertically stacked multilayer Gallium Selenide separated by low-index PMMA spacer layer

Biswas, R and Prosad, A and Lal Krishna, AS and Menon, S and Raghunathan, V (2022) Enhanced Second Harmonic Generation from vertically stacked multilayer Gallium Selenide separated by low-index PMMA spacer layer. In: 2D Photonic Materials and Devices V 2022, 20 - 24 February 2022, Virtual, Online at San Francisco, California, United States.

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Official URL: https://doi.org/10.1117/12.2609737


ε-Gallium Selenide (GaSe) is a well-known two dimensional (2D) layered material from the group III-V semiconductor family exhibiting strong second-order optical nonlinearity. In spite of the strong optical nonlinearity, the overall second harmonic generation (SHG) emission does not increase indefinitely with GaSe film thickness due to material absorption at the SHG wavelength and phase mismatch between the interacting waves. The backward propagating SHG signal is found to reach a maximum for ~20-30nm GaSe thickness for GaSe layer on silicon dioxide (SiO2) of thickness in the range of 100-300nm on silicon (Si) substrate. Here we report a significant enhancement of SHG by using vertically stacked multilayer GaSe separated by a low-index Poly-methyl methacrylate (PMMA) layer. The thickness for each layer is optimized using a hybrid evolutionary optimization algorithm combining Genetic algorithm with a stochastic hill-climbing search method, with the SHG emission used as the figure of merit for optimization. The final optimized structure consists of a 195 nm PMMA layer sandwiched between two 40nm GaSe on top of a 130 nm SiO2 deposited on a silicon substrate. Experimentally, we obtained 303-times and 246-times enhancement in the SHG signal from the optimized configuration compared with a single 40 nm GaSe on a 300 nm and a single 80nm GaSe on 130 nm SiO2/Si substrate, respectively. Such optimized structure underscores the importance of micro-cavity engineering by choosing appropriate 2D material and interspacer thickness to enhance SHG emission from popular 2D materials. © 2022 SPIE.

Item Type: Conference Paper
Publication: Proceedings of SPIE - The International Society for Optical Engineering
Publisher: SPIE
Additional Information: The copyright for this article belongs to the SPIE.
Keywords: Esters; Gallium compounds; Harmonic analysis; Harmonic generation; III-V semiconductors; Layered semiconductors; Multilayers; Nonlinear optics; Selenium compounds; Silica; Silicon oxides; Stochastic systems; Substrates, 2d material; Gallium selenides; Harmonics generation; Low index; Optimisations; Optimized structures; Poly(methyl methacrylate); Poly-methyl methacrylates; Second harmonics; Silicon substrates, Genetic algorithms
Department/Centre: Division of Electrical Sciences > Electrical Communication Engineering
Date Deposited: 22 Jun 2022 09:31
Last Modified: 22 Jun 2022 09:31
URI: https://eprints.iisc.ac.in/id/eprint/73942

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