Wide band UV/Vis/NIR blazed-binary reflective gratings: two lithographic techniques investigation

Mane-Si Laure Lee,Nicolas Tetaz,Saroj Mahalik,Anne Delboulbé,Roman Windpassinger,Raphaël Guillemet,Patrick Garabedian,Julie Cholet,Tino Benkenstein,Brigitte Loiseaux,Thomas Flügel-Paul,Susann Sadlowski,C Sibilia,A Belardini,G Pauliat

doi:10.1051/epjconf/202125512014

Abstract

We report on subwavelength reflective gratings for hyperspectral applications operating in the 340 nm-1040 nm spectral range. The blazed grating period is 30 μm and is composed of 2D subwavelength binary structures with sizes in-between 120 nm and 350 nm. We demonstrate the manufacturing of gratings on 3” wafers by two lithography technologies (e-beam or nanoimprint) followed by dry etching process. These subwavelength gratings enable broadband efficiency which is in average 15%-20% above the efficiency requirement for next generation of spectro-imagers for Earth observation missions and a wavefront error that is much smaller than the 100 nm requirement for space application.

Highlights

Generation of spectro-imagers for future Earth observation missions requests ultra-wide band operation, very large field of view but small volume
We report on subwavelength reflective gratings for hyperspectral applications operating in the 340 nm-1040 nm spectral range
These subwavelength gratings enable broadband efficiency which is in average 15%-20% above the efficiency requirement for generation of spectro-imagers for Earth observation missions and a wavefront error that is much smaller than the 100 nm requirement for space application

Summary

Introduction

Generation of spectro-imagers for future Earth observation missions requests ultra-wide band operation, very large field of view but small volume. Classical continuous reflective saw-tooth profile blazedgratings offer peak efficiencies up to ~90% (mainly limited by the reflectivity of the metallic material) but it decreases significantly when approaching the band edges in the UV and NIR regions. To overcome this limited spectral efficiency, several approaches have been proposed in the literature. Proposed for transmission gratings [2, 3], it has been applied recently to reflection gratings [4] Another alternative is the so-called “multi-blaze” or “multi-angle” approach [5, 6].

Subwavelength gratings fabrication

Optical measurements

Conclusion