An approach for calculating arbitrary-order diffraction through hole-array based on thin microcavity theory

An approach for calculating the optical diffraction coefficients through a subwavelength hole-array embedded in a suspending thin metal layer is investigated based on the rigorous coupled wave analysis method and thin microcavity theory. In this approach, the electromagnetic field components in the reflected and transmitted regions and diffraction coefficients of arbitrary orders are derived, respectively, and some enhanced diffraction phenomena are discussed in detail, which are then verified via finite element (FE) simulation. Subsequently, the effects of structural and material parameters of holey thin film including film material, incident angle, hole geometry, and duty cycle of periodic array layer on the transmittance are analyzed. The relevant results show that the duty cycle is the main influence factor, and with the suitable duty cycle the optical transmittance through the free-standing metal layer can be enhanced as high as 0.8 in the visible region. All these findings may be utilized in the wavelength tuning of subwavelength optics.