Asymmetric transmission through metallic grating with dielectric substrate

We show the phenomenon of asymmetric TM light transmissions through metallic grating with dielectric substrate, which depends on neither magneto-optical nor nonlinear materials. Numerical evidence shows that the asymmetry in total transmissions is induced by first-order transmissions, while the zero-order transmissions keep symmetric. With optimized parameters, the asymmetry can be as high as 0.4279.