HVPE-based orientation-patterned GaAs: added-value for non-linear applications.
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HVPE-based orientation-patterned GaAs : added-value for non-linear applications. Faye D., Lallier E., Grisard A., Gérard B. and Gil-Lafon E. 1 THALES RESEARCH & TECHNOLOGY (TRT), Domaine de Corbeville, 91404 Orsay, FRANCE. 1 LASMEA UMR CNRS 6602, Campus Universitaire des Cézeaux, 63177 Aubière, FRANCE. ABSTRACT A new route is presented for the development of Orientation-Patterned Gallium Arsenide (OP-GaAs) for both guided and non-guided optical applications. The method is based on the use of the near-equilibrium growth process HVPE (Hydride Vapour Phase Epitaxy) that enables thick, high quality and orientation-preserving regrowth over dimensions fully compatible with targeted applications. The control of the growth anisotropy permits to preserve the original periodic arrangement of the initial template so that OP-GaAs substrates can be fabricated with pattern width and structure thickness ranging respectively from 1.8 to 110µm and 20 to 500µm. Such a large scope of dimensions appears useful either for bulk structures such as Optical Parametric Oscillators (OPO) or telecommunication applications. As an example, we suggest that combining this growth method with mechano-chemical polishing process could decrease propagation losses on AlGaAs waveguide structures for frequency conversion in telecom bands.
INTRODUCTION Zincblende semiconductor materials such as GaAs offer many potential advantages for applications in nonlinear optical frequency conversion devices. Indeed, their high intrinsic quadratic nonlinearity ( d14= 96pm/V) compared to PPLN ( Periodically Poled Lithium Niobate), transparency (1µm to 12µm), polarization independence and potential integration with semiconductor lasers are well matched to operate either in mid-IR sources or telecommunication network as WDM-oriented frequency converter. However, the crystallographic properties of GaAs (cubic point group symmetry) and its lack of spontaneous ferroelectric polarization hamper traditional birefringent phasematching (BPM) and well-known electric-field poling technique. To solve that problem, several approaches have been proposed and can be divided in two categories: artificial introduction of birefringence or modulation of the non-linear susceptibility χ (2) to realize quasi-phasematching (QPM). The first concept consists in the deposition of GaAs/oxidised AlAs multilayer systems to induce a strong birefringence form [1, 2]. The second one involves the growth of asymmetric quantum wells or superlattice waveguides with selective disordering, both techniques sharing a high fabrication complexity. Furthermore, these methods led to disappointing reported generation efficiencies, due to high scattering losses on the one hand, and to weak or nonuniform χ (2) modulation on the other hand. A more flexible technique to achieve quasi-phasematching lies in periodic modulation of the non-linear susceptibility χ (2). This is typically reached by fabricating templates with OrientationPatterned surface (OP-semiconductors), then growing waveguide structures or bulk
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