Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator.

N Vukovic,J R Sparks,N Healy,A C Peacock,P Horak,J V Badding

doi:10.1038/srep11798

Abstract

Whispering gallery mode microresonators made from crystalline materials are of great interest for studies of low threshold nonlinear phenomena. Compared to amorphous materials, crystalline structures often exhibit desirable properties such as high indices of refraction, high nonlinearities, and large windows of transparency, making them ideal for use in frequency comb generation, microlasing and all-optical processing. In particular, crystalline materials can also possess a non-centrosymmetric structure which gives rise to the second order nonlinearity, necessary for three photon processes such as frequency doubling and parametric down-conversion. Here we report a novel route to fabricating crystalline zinc selenide microcylindrical resonators from our semiconductor fibre platform and demonstrate their use for tunable, low power continuous wave second harmonic generation. Visible red light is observed when pumped with a telecommunications band source by a process that is phase-matched between different higher order radial modes, possible due to the good spatial overlap between the pump and signal in the small volume resonator. By exploiting the geometrical flexibility offered by the fibre platform together with the ultra-wide 500–22000 nm transmission window of the ZnSe material, we expect these resonators to find use in applications ranging from spectroscopy to quantum information systems.

Highlights

Wavelength semiconductor materials such as AlN12,13, GaAs14 and AlGaAs15, to access the χ(2) nonlinearity both for nonlinear frequency conversion and electro-optic modulation
We have developed a method to fabricate microcylindrical resonators starting from our semiconductor fibre platform that have ultra-smooth surfaces defined by the silica capillary into which the material is deposited[16]
We present characterizations of the first compound semiconductor fibre-based resonators and demonstrate their use for low threshold, continuous emission of red light via second harmonic generation (SHG)

Summary

Introduction

Wavelength (nm) semiconductor materials such as AlN12,13, GaAs14 and AlGaAs15, to access the χ(2) nonlinearity both for nonlinear frequency conversion and electro-optic modulation. These planar-based semiconductor resonators are defined using standard photolithography and etching methods, resulting in surface roughness levels on the order of a few nanometers. We have developed a method to fabricate microcylindrical resonators starting from our semiconductor fibre platform that have ultra-smooth surfaces defined by the silica capillary into which the material is deposited[16]. We present characterizations of the first compound semiconductor fibre-based resonators and demonstrate their use for low threshold, continuous emission of red light via second harmonic generation (SHG). The flexibility of the fibre platform opens up new routes to developing continuously tunable sources that could be phase-matched across large regions of the broad transmission window of the material

Methods

Results

Conclusion