Interfacial second harmonic generation switching with 2D monolayer/VO₂ heterostructure

To establish a facile nonlinear optical switching mechanism activated by thermal field, that is compatible with on-chip integration, we develop a physical model to quantify the interfacial second harmonic generation (SHG) of 2D monolayer/3D phase-changing material heterostructure. Our results show that heat-induced phase transition of VO2 can realize temperature-reversible interfacial SHG switching, with an ON-OFF ratio of about 3 and a low temperature threshold of about 60 C-degrees. Experimental results can be well addressed by quantitative calculations based on the physical model. This work constitutes substantial insights into interfacial SHG switching, which will benefit design and construction of on-chip nonlinear optical devices based on 2D monolayers.