Cavity Controlled Nonlinear Optical Filtering of Second Harmonic Signal in Metal Organic Framework Single Crystals

Abstract In this study, a novel method is presented for enhancing second harmonic generation (SHG) by exploiting the natural Fabry‐Pérot cavity effect within PCN‐250 metal‐organic framework (MOF) microplates. PCN‐250, recognized for its chemical stability and moisture resistance, exhibits strong anisotropic second‐order nonlinear susceptibility, making it an excellent candidate for SHG applications. By harnessing the cavity‐controlled SHG emission, a significant enhancement in SHG efficiency under 1030 nm femtosecond laser excitation is achieved. The study involved eight single‐crystalline microplates with varying thicknesses, demonstrating a tenfold increase in SHG signal strength when the detuning (Δ) between the cavity mode and SHG signal is approximately zero. Simulations using a nonlinear transfer matrix method (TMM) confirms that resonance‐driven SHG enhancement occurred only at 1030 nm, with a selective nonlinear optical filtering effect. This approach introduces a cost‐effective technique for developing highly efficient SHG materials, with broad applications in telecommunications, sensing, and quantum optics.