Efficient telecom to visible wavelength conversion in doubly resonant gallium phosphide microdisks

Resonant second harmonic generation between 1550 nm and 775 nm with normalized outside efficiency >3.8×10−4 mW−1 is demonstrated in a gallium phosphide microdisk supporting high-Q modes at visible (Q∼104) and infrared (Q∼105) wavelengths. The double resonance condition is satisfied for a specific pump power through intracavity photothermal temperature tuning using ∼360 μW of 1550 nm light input to a fiber taper and coupled to a microdisk resonance. Power dependent efficiency consistent with a simple model for thermal tuning of the double resonance condition is observed.