Broadband antireflection enhancement by triangular grating microstructure in the resonance domain

• The broadband antireflection characteristics of the triangular grating microstructure are investigated.
• Diffraction pattern of grating is clearly demonstrated.
• The transmittance of the external reflection and the internal reflection grating in the resonant domain is analyzed.
• The electric field distribution is intuitively displayed.

It is well known that broadband antireflective characteristics are frequently realized by using subwavelength tapered micro- or nanostructures. In this paper, we propose that the triangular grating in the resonance domain with period larger than the incident wavelength can also possesses broadband and wide angle antireflective performance and polarization selection. The diffraction pattern for the external reflection grating and the internal reflection one is demonstrated by the rigorous vector diffraction theory. It is found that the total transmittivity with TE polarized illumination is clearly less than that for TM polarization. The aspect ratio of grating is a significant parameter to broadband antireflection performance. For the external reflection grating, the broadband antireflection function can be achieved with the aspect ratio larger than 1.5 for both polarization modes in the resonant domain. For the internal reflection grating, the narrow band antireflection properties are demonstrated for TE polarization with higher aspect ratio. And the broadband antireflection characteristics can be revealed at the aspect ratio higher than 4.0 in the resonance domain for TM polarization. Besides, in order to determine intuitively diffraction pattern and antireflection performance, the electric field distribution was calculated for both types of triangular profile in the resonant domain, and the aspect ratio of the grating is crucial to the total transmittance.