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Two-dimensional (2D) transition metal dichalcogenides exhibit strong excitonic responses, direct bandgaps, and remarkable nonlinear optical properties, making them highly attractive for integrated photonic, optoelectronic, and quantum applications. Here, we present a large-area freestanding membrane photonic platform that achieves exceptional enhancement of light–matter interactions in monolayer WSe2 via quasi-bound states in the continuum (quasi-BICs). The freestanding architecture effectively suppresses radiative losses and supports high-Q optical resonances, leading to enhanced light–matter interactions. This results in significant photoluminescence emission and second-harmonic generation (SHG) enhancement factors of 1158 and 378, respectively, with spatial uniformity sustained across a 450 × 450 µm 2 area. This uniform SHG enhancement further enables polarization-resolved mapping of crystal orientation and grain boundaries, offering a practical method for large-area structural characterization of 2D materials. Moreover, femtosecond-pumped SHG spectra reveal multiple narrowband peaks originating from distinct quasi-BIC modes—providing direct spectral evidence of resonantly enhanced nonlinear coupling. The combined attributes of strong optical enhancement, spectral selectivity, and wafer-scale compatibility establish this platform as a scalable interface for 2D semiconductor integration in next-generation optoelectronic, nonlinear, and quantum photonic technologies.

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  This is the pre-peer reviewed version of the following article: F.-L.Hsieh, C.-Z.Deng, S.-K.Huang, et al. “Large-Area Photonic Membranes Achieving Uniform and Strong Enhancement of Photoluminescence and Second-Harmonic Generation in Monolayer WSe2.” Small Methods10, no. 4 (2026): e01693, which has been published in final form at https://doi.org/10.1002/smtd.202501693. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

Keyword: bound states in the continuum, membrane , PL enhancement, second-harmonic generation, transition metal dichalcogenides, WSe2

Date published: 2026-02-02

Publisher: Wiley

Journal:

• Small Methods (ISSN: 23669608) vol. 10 issue. 4 e01693

Funding:

• Japan Society for the Promotion of Science JP23K26155
• Japan Society for the Promotion of Science JP25KF0083
• National Science and Technology Council 114‐2112‐M‐002‐032‐MY3
• National Science and Technology Council 113‐2124‐M‐002‐007‐

Manuscript type: Author's version (Submitted manuscript)

MDR DOI: https://doi.org/10.48505/nims.6225

First published URL: https://doi.org/10.1002/smtd.202501693

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Updated at: 2026-03-18 16:23:07 +0900

Published on MDR: 2026-03-21 13:26:21 +0900