ANTIREFLECTION STRUCTURES WITH USE OF MULTILEVEL SUBWAVELENGTH ZERO-ORDER GRATINGS

It is known that the zero-order two-phase-level gratings with a period much smaller and a thickness much larger than the wavelength may have antireflection properties the same as appropriate dielectric layers u nder normal incidence. On the basis of the rigorous coupled-wave analy sis method formulation, it is shown that multilevel unidimensional pha se gratings, for both TE and TM polarization, are functionally equival ent to antireflection structures of multilevel dielectric layers, even if the period is close to the wavelength. (C) 1997 Optical Society of America.