Thermally activated resonant grating using a vanadium dioxide waveguide

E K Koussi,S Reynaud,D Jamon,O Parriaux,T Kämpfe,Y Jourlin,I Verrier,F Bourquard,H Bruhier

doi:10.1364/ome.413373

Abstract

In this work, we report on the design of a one-dimensional subwavelength resonant grating comprised of a fused silica substrate and a bi-layer waveguide, consisting of a solgel synthetized anatase TiO2 layer followed by a thin VO2 layer that is applied using pulsed laser deposition and rapid thermal annealing. A TE waveguide mode is excited under normal incidence in the VO2/TiO2 bi-layer via a positive photoresist based grating printed on top, leading to high resonant reflection at room temperature. Increasing the temperature to about 68°C causes the VO2 to undergo a dielectric to metallic transition accompanied by optical modifications in the IR region, canceling the resonance effect. This thermally triggered absorber/emitter tunable configuration enabling the on and off switching of optical resonant excitation in a reversible manner is proposed for passive Q-switching self-protecting devices for high power lasers in the IR wavelength range. Modeling of the optimized temperature dependent resonant waveguide and preliminary experimental results are presented.

Highlights

Optical switches induced by electric [1], thermal [2], acoustic [3], or magnetic [4] effects are well known and widely reported
VO2 has been one of the most attractive candidates for realizing an efficient optical switching effect because of the ability to change its optical properties around a transition temperature of ∼68°C [5,6,7,8], where dielectric to metal transition occurs
Structured VO2 has been used for thermal rectification of radiative diodes and thermal transistors [13,14]. 1D gold gratings, situated on a VO2 film and a bottom Au layer have been proposed for a temperature dependent excitation of a magnetic resonance [15]

Summary

Introduction

Optical switches induced by electric [1], thermal [2], acoustic [3], or magnetic [4] effects are well known and widely reported. Unlike many of the above-mentioned devices that rely on metals for resonant effects, the structure studied here uses a dielectric only system using waveguide excitations for the optical switching, which is fabricable with fairly standard lithographic techniques. This allows theoretically to work with very low absorption, allowing for a tunable, waveguide mode resonance in reflection applicable to passive Q-switching applications in lasers as proposed in [24].

Principle of waveguide resonance and switching effect

Determination of the refractive indices of the layer

Fabrication and characterization process

Conclusion