Nonreciprocal optical switch based on phasechange gratings

Phase-change materials have promising applications in thermophotovoltaics, thermal management and nonreciprocal thermal radiation. The use of crystalline transitions in phasechange materials provides a new path to realize nonreciprocal modulation. This work presents a nonreciprocal switch based on the one-dimensional gratings with phase-change material Ge 2 Sb 2 Te 5 on a Weyl semimetal. The rigorous coupled-wave analysis is employed in the switch design and optimization. In the amorphous state, the switch present the nonreciprocity of 0.9735 at 12.01 µm for TE polarization and 0.9142 at 11.661 µm for TM polarization, respectively. In the crystalline state, the nonreciprocity at both polarizations decreases to be below 0.06, exhibiting distinct "on" and "off" states. The interrelationship between angle of incidence, azimuth angle and nonreciprocity has been investigated to reveal the background scheme. The proposed switch holds good fabrication tolerance that is valuable in practical application. The obtained results provide a new avenue in the field of nonreciprocal thermal radiation, energy harvesting and conversion.