Achieving angle-insensitive spectrum filter with the slit nanoresonator array structure

Abstract

The spectrum filtering behavior of the slit nanoresonator array structure is based on the coupling between the slit resonance and the Wood’s anomaly of grating array, and therefore has angle dependence, which is not desirable for some applications. To achieve an angle-insensitive spectrum filter, such a coupling should be disrupted. We show that reducing the period of the slit array helps decouple these two resonances. Additionally, by enhancing the light confinement inside the slits through either shrinking the slit width or filling the slits with a high-index medium, a narrow transmission peak is maintained at a small period so that an angle-insensitive spectrum filter is achieved.