Photothermal optical modulation of ultra-compact hybrid Si-VO₂ ring resonators.

We demonstrate photothermally induced optical switching of ultra-compact hybrid Si-VO₂ ring resonators. The devices consist of a sub-micron length ~70 nm thick patch of phase-changing VO₂ integrated onto silicon ring resonators as small as 1.5 μm in radius. The semiconductor-to-metal transition (SMT) of VO₂ is triggered using a 532 nm pump laser, while optical transmission is probed using a tunable cw laser near 1550 nm. We observe optical modulation greater than 10dB from modest quality-factor (~10³) resonances, as well as a large -1.26 nm change in resonant wavelength Δλ, resulting from the large change in the dielectric function of VO₂ in the insulator-to-metal transition achieved by optical pumping.