Fig. 1. Structure of metagrating. (a)(c) Structure of single-layer and double-layer metagratings; (b)(d) cross section of the structural elements of the single-layer and double-layer metagratings

Fig. 2. Structure of optical waveguide

Fig. 3. Light field distribution at 18 mm away from the metagrating under different periodW3

Fig. 4. Far-field intensity distribution at W3 of 378 nm

Fig. 5. Light field distribution of double-layer metagratings at different rectangular width W5. (a)-(d) Light field distribution at W5of249, 219, 209, 150 nm, respectively

Fig. 6. Relationship between rectangular height H2 and transmittance of double-layer metagrating