Abstract
Due to adjustable modal birefringence, suspended AlGaAs optical waveguides with submicron transverse sections can support phase-matched frequency mixing in the whole material transparency range, even close to the material bandgap, by tuning the width-to-height ratio. Furthermore, their single-pass conversion efficiency is potentially huge, thanks to the extreme confinement of the interacting modes in the highly nonlinear and high-refractive-index core, with scattering losses lower than in selectively oxidized or quasi-phase-matched AlGaAs waveguides. Here we compare the performances of two types of suspended waveguides made of this material, designed for second-harmonic generation (SHG) in the telecom range: (a) a nanowire suspended in air by lateral tethers and (b) an ultrathin nanorib, made of a strip lying on a suspended membrane of the same material. Both devices have been fabricated from a 123 nm thick AlGaAs epitaxial layer and tested in terms of SHG efficiency, injection and propagation losses. Our results point out that the nanorib waveguide, which benefits from a far better mechanical robustness, performs comparably to the fully suspended nanowire and is well-suited for liquid sensing applications.
Highlights
Recent technological advances have allowed reducing the size of semiconductor photonic devices to the sub-micrometer scale, with a remarkable impact in several research domains like integrated optofluidics [1] and nonlinear photonics [2]
High-contrast AlGaAs nonlinear photonic structures have been reported at the nanoscale level, based on either selective oxidation of an AlAs substrate [16,17] or epitaxial liftoff followed by bonding on glass [18], for both second-harmonic generation (SHG) [16,17,18] and spontaneous parametric down-conversion (SPDC) [19]
We demonstrated phase-matched optical SHG from the telecom range in suspended submicron AlGaAs waveguides with two different designs: a nanowire and a nanorib
Summary
Recent technological advances have allowed reducing the size of semiconductor photonic devices to the sub-micrometer scale, with a remarkable impact in several research domains like integrated optofluidics [1] and nonlinear photonics [2]. High-contrast AlGaAs nonlinear photonic structures have been reported at the nanoscale level, based on either selective oxidation of an AlAs substrate [16,17] or epitaxial liftoff followed by bonding on glass [18], for both second-harmonic generation (SHG) [16,17,18] and spontaneous parametric down-conversion (SPDC) [19] Their higher refractive-index step (∆n ≈ 1.5) made them suitable for shallow etching fabrication, with a huge impact on integration up until the demonstration of the first χ(2) metasurfaces [20,21]. APlrlodpeavgiacteisonwelroessteessteadt uωsinagntdwo2ωconwtienrueoumsleyastuunreadbleblyasaecrqsuoiurrincegs: FaaCbWry–ePxeterrontaltrcaanvsimtyilsassioern diniotedrefeermenitcteinfgribnegtews einenon1.-5paunrpdo1s.e6 pμrmocaenssdeda s2i0n0glμemmloodnegCwWavTeig:suaipdpeshitreermtuinnaabteledbbeytwflaeet nIC0P.7eatcnhde1d μfamc.etBso(twh hlaicsherhbaevaemhsigbhuettrcroeuflpelcetdivaittyththe ainnptuhteatnadpetrheedocuotpuunttewrpitahrtms)i.cTrohleencsoemd,bsininegdlelomsso–dreefolepctticioanl ficboeerfsfi.cLieinnet aRr' a=nRd enxopn(l-iαneLa)rcaspnebcetraexhtaravcetebdeebnyrethcoercdoendtrbaystinKjeocftitnhgeatnradntsumniisnsgiothnefrlainsgeressoausrfcoelslowwhsi:le detecting the outcoupled light either by an InGaAs or an Si photodiode
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