反射式共振腔型亚波长波片

We propose a quarter-wave plate using metal-insulator-metal (MIM) resonant structure with sub-wavelength rectangular annular arrays (RAA) patterned in the upper Au film. It is found that by manipulating asymmetric width of the annular gaps along two orthogonal directions and the thickness of the dielectrics between the two metal films, the reflected amplitude and phase of the two orthogonal electric components can be well controlled, in which the localized surface plasmon resonance dip can be flattened with the cavity length. A quarter-wave plate has been realized at 1.55μm, in which the phase difference variation of less than 2% of the pi/2 between the two orthogonal components can be obtained in an ultra-wide wavelength range of about 130nm, and the reflectivity is up to ~90% within the whole working wavelength band.