Enhancement of second harmonic generation in two-dimensional materials with dual-stopband distributed Bragg reflector

As a prominent branch of nonlinear optics (NLO), second-harmonic generation (SHG) has been widely studied in fields such as optics, electronics, and materials science. Due to their high conversion efficiency and relaxed phase matching constraints, two-dimensional (2D) materials have become an attractive platform for SHG research. In this work, monolayer MoSe_2 was used as the active material, and a dual-stopband distributed Bragg reflector (DBR) structure was fabricated by plasma-enhanced chemical vapor deposition (PECVD) to enhance the SHG efficiency of monolayer MoSe_2. The DBR provided substantial enhancement at both the excitation and emission wavelengths. Compared to MoSe_2 on a Si substrate, the sample on the DBR exhibited an SHG signal enhancement of over 4000 times. Polarization-dependent measurements showed that the SHG response of MoSe_2 on the DBR retained the same polarization dependence as that on the Si substrate. Furthermore, temperature-dependent measurements confirmed that the variation of the SHG signal with temperature followed a consistent trend for MoSe_2 on both substrates.