A thermally controlled high-Q metasurface lens

Dynamic metasurface control is a promising yet challenging prospect for next generation optical components. Here, we design and characterize a thermally controllable metasurface lens, with a high-quality-factor (high-Q) resonance working as both the basis of the lensing behavior and method for efficient modulation. Our high-Q lens is constructed via a zone plate architecture comprised of alternating regions with and without resonant character. Non-resonant regions block transmission, while resonant regions—with measured Qs up to ∼1350—transmit only on resonance. By leveraging the thermo-optic effect, we dynamically control the spectral position of the high-Q resonance to achieve wavelength selectivity of the focusing behavior. Due to the sharp spectral linewidth and amplitude variation of the high-Q resonance, thermal tuning can further result in metasurface switching, where the lensing behavior is changed between on and off states. For a device utilizing only moderate Q-factors of ∼350, the resonance's FWHM can be shifted with temperature changes of only 50 °C, and the device can be fully switched off when operating at 100 °C. Our work provides an initial experimental demonstration of dynamic control of a local high-Q wavefront shaping metasurface.