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

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.