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 similar 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 similar to 350, the resonance's FWHM can be shifted with temperature changes of only 50 degrees C, and the device can be fully switched off when operating at 100 degrees C. Our work provides an initial experimental demonstration of dynamic control of a local high-Q wavefront shaping metasurface.