Abstract
We report on the fabrication of gallium phosphide (GaP) nanowaveguides of controlled dimensions, as small as 0.03 μm and aspect ratio in excess of 20, using focused ion beam (FIB) milling. A known limitation of this fabrication process for photonic applications is the formation of gallium droplets on the surface. We demonstrate a post-fabrication step using a pulsed laser to locally oxidize the excess surface gallium on the FIB milled nanostructures. The process significantly reduces the waveguide losses. The surface optical quality of the fabricated GaP nanowaveguides has been evaluated by second-harmonic generation experiments. Surface and bulk contributions to second-order optical nonlinearities have been identified by polarization measurements. The presented method can potentially be applied to other III-V nanostructures to reduce optical losses.
Highlights
Focused ion beam (FIB) technology has become increasingly attractive since the introduction of the liquid metal ion source (LMIS) [1,2]
We present the fabrication of gallium phosphide (GaP) multilayer slab waveguides (MSWs) by FIB
By measuring the second harmonic generation (SHG) of light from the MSWs, we demonstrate that this fabrication procedure guarantees high second-order nonlinear optical properties of the structures, including but not limited to the surface properties
Summary
Focused ion beam (FIB) technology has become increasingly attractive since the introduction of the liquid metal ion source (LMIS) [1,2]. A post-fabrication step in which the FIB milled MSWs are treated by pulsed laser irradiation in ambient air is used to recover the optical properties by oxidising the surfaces gallium droplets.
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