Smallest aspect-ratio form-birefringence half-wave plate

Thomas Kampfe (1) , Pierre Sixt (2) , Denis Renaud (3) , Armelle Lagrange (2) , Fabrice Perrin (2) , Remi Torres (4) , Guillaume Gomard (5, 6) , Olivier Parriaux (1)

1 LHC - Laboratoire Hubert Curien
2 CEA-LETI - Commissariat à l'énergie atomique et aux énergies alternatives - Laboratoire d'Electronique et de Technologie de l'Information
3 SDOT - Services des Opérations Technologiques
4 ALPhANOV
5 INL - Photonique - INL - Nanophotonique
6 INL - PV - INL - Photovoltaïque

Subwavelength 0th order gratings permit to create a phase-shift between the polarized 0th order grating modes propagating down the slits and grooves of a binary corrugation, and to transform the polarization of an incident beam. The phase-shift per unit height of the grating is an increasing function of the refractive index difference between ridges and grooves. If the ridges are made by photolithography in a resist or by polymer embossing, the low refractive index leads to a very large corrugation aspect ratio (approx. 4 for a half-wave phase-shift) that is difficult to fabricate and/or provides insufficient mechanical stability. If the ridges are made in a high index non-organic material (e.g. a semiconductor) the needed depth is reduced (although still notably larger than 1 for a half-wave phase-shift). However, in this case due to a more significant Fabry-Perot effect between the upper and lower boundaries of the 0th order grating, high transmission is guaranteed only if its resonance condition is ensured for both polarizations simultaneously. Using an inventive design by phase management of the involved grating modes we have found that all three conditions (pi phase-shift between TE and TM and both Fabry-Perot resonances) can indeed be satisfied in a binary grating of reasonable aspect ratio when the substrate has a refractive index notably smaller than the ridges.

Domaines: Optique [physics.optics]

Thomas Kampfe, Pierre Sixt, Denis Renaud, Armelle Lagrange, Fabrice Perrin, et al.. Smallest aspect-ratio form-birefringence half-wave plate. 10th International Workshop on High Aspect Ratio Micro and Nano System Technology (HARMNST), Apr 2013, Berlin, Germany. pp.Poster T31. ⟨hal-01021074⟩