Nonreciprocal absorption properties of a magneto-optical microstructure with suppressed photothermal effects

Abstract

In this work, a magneto-optical microstructure of titanium (Ti)-doped ellipsoidal particles is designed, and an improved equivalent medium theory (EMT) combined with thin-film optics theory are proposed. The doped magneto-optical microstructures obtain strong broadband nonreciprocal absorption spectra in the near-infrared band, and the nonreciprocal absorption spectra remain above 0.9 at 4.5 to 5μm with nonreciprocity up to 0.53. In addition, the effects of dopant layer thickness, filling ratio and incident angle on the nonreciprocal absorption are also discussed in detail. It worth nothing that the photothermal effect of the magneto-optical microstructures are numerically studied. The optical power of the incident light affects the overall temperature rise, which results in nonreciprocal effect due to the unequal forward and reverse incident absorption spectra. It is found that the photothermal effect for our magneto-optical model caused by the plasmon effect does not produce a normal high temperature rise. The highest temperature rise is only 5.45 K for a single cycle irradiated by 50 mW of optical power, which effectively suppresses the photothermal effect, this is important for maintaining optical devices such as solar cells, optical isolators, and infrared camouflagers at optimal operating temperatures. This property provides new ideas for the design of solar cells, infrared camouflage, optical isolators, radiation-cooled films, and other applications.