Fig. 7

Nonreciprocal optical components. a, b A nonreciprocal waveguide based on magnetic Weyl semimetals. a The geometry consists of a Weyl semimetal film surrounded by two semi-infinite dielectrics. b The light dispersion at the waveguide. The red lines (\(\textrm{SPP}_>\)) and blue lines (\(\textrm{SPP}_<\)) denote the forward and backward nonreciprocal surface plasmon polaritons, respectively. The cyan regions denote the nonreciprocal waveguide modes. c, d A Voigt isolator based on magnetic Weyl semimetals. c The geometry consists of three unit cells. Each unit cell comprises three material layers. The dark and bright grey layers are made of Weyl semimetals with opposite chiral shifts as indicated by the yellow arrows. The yellow layer is made of crystalline silicon (c-Si). The blue and red arrows denote forward and backward illuminations, respectively, at an incident angle \(\theta = 45.6^\circ\). d The transmittance spectra in the forward (blue) and backward (red) directions. Also shown is the isolation ratio (green). e, f An isolator based on a photonic crystal slab made of Weyl semimetal and silicon. e The geometry consists of a photonic crystal slab made of Weyl semimetals (green) and silicon (gray) and a uniform silicon slab separated by an air gap. f The reflectance and transmittance spectra in the forward (red) and backward (blue) directions. Figures are reproduced with permission from a, b Ref. [6], Copyright 2018 American Physical Society; c, d Ref. [7], Copyright 2020 John Wiley and Sons; e, f Ref. [8], Copyright 2021 American Chemical Society