Design, fabrication. and integration of HIC glass waveguides on a silicon platform

We demonstrate Si-CMOS-compatible lift-off fabrication of chalcogenide glass waveguides monolithically integrated on a silicon platform. As a novel route of glass film patterning, lift-off allows several benefits: leverage with Si-CMOS process compatibility; ability to fabricate single-mode waveguides with core sizes down to submicron range; reduced sidewall roughness; and wide applicability to other non-silica glass compositions. High-index-contrast (HIC) single-mode strip waveguides have been fabricated with from several glass target compositions including Ge23Sb7S70, As2S3, As36Ge6S58, As36Sb6S58 and TeO2. We measured Ge-Sb-S waveguides with low loss and excellent wafer-scale uniformity. We have experimentally demonstrated propagation loss reduction via graded-index (GRIN) cladding layers in HIC glass waveguides. These efforts have shown that scattering loss arising from sidewall roughness can be significantly reduced without compromising the high-index-contrast condition by inserting thin GRIN cladding layers with refractive indices intermediate between the core and topmost cover of a strip waveguide.

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