Large bandwidth, highly efficient optical gratings through high index materials

TL;DR

This paper presents the design and analysis of high-efficiency, broadband dielectric gratings with high index materials, achieving superior performance over traditional gratings in various geometries through rigorous numerical methods.

Contribution

It introduces novel dielectric grating designs with high index layers that significantly improve bandwidth and efficiency compared to existing gratings.

Findings

Doubled -1dB bandwidth in dielectric TIR gratings.

Tripled -1dB bandwidth in immersed transmission gratings.

Achieved near 100% diffraction efficiency at design wavelength.

Abstract

We analyze the diffraction characteristics of dielectric gratings that feature a high index grating layer, and devise, through rigorous numerical calculations, large bandwidth, highly efficient, high dispersion dielectric gratings in reflection, transmission, and immersed transmission geometry. A dielectric TIR grating is suggested, whose -1dB spectral bandwidth is doubled as compared to its all-glass equivalent. The short wavelength diffraction efficiency is additionally improved by allowing for slanted lamella. The grating surpasses a blazed gold grating over the full octave. An immersed transmission grating is devised, whose -1dB bandwidth is tripled as compared to its all-glass equivalent, and that surpasses an equivalent classical transmission grating over nearly the full octave. A transmission grating in the classical scattering geometry is suggested, that features a buried high index layer. This grating provides effectively 100% diffraction efficiency at its design wavelegth, and surpasses an equivalent fused silica grating over the full octave.