16 February 2010 Silicon photonics: ready to wafer-bonding fibre grating coupler
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Proceedings Volume 7606, Silicon Photonics V; 760618 (2010) https://doi.org/10.1117/12.839679
Event: SPIE OPTO, 2010, San Francisco, California, United States
Abstract
Silicon nanophotonic circuits can exhibit a very high level of functional integration that can be added directly into IC layers. Such an integration is typically performed by wafer to wafer bonding: the first wafer having the optical and optoelectronic layers, the second wafer having the microelectronic layers. After the substrate removing at the photonic wafer side, the optical structures appear then face down when compared with the initial fabrication. This structure flip may be detrimental to the performance of fibre grating couplers as there may be no more optimized layers below as with gratings on SOI. We present an efficient fibre grating coupler with a bottom mirror that anticipates the structure flip. In this approach the mirror is first coated above the encapsulation layer of the fibre grating coupler in order to appear below it after the optical layers integration onto an IC wafer. This way the thickness between the grating and the bottom mirror, which is a very sensitive parameter, remains under control whatever the wafer to wafer bonding process tolerances. For this design we can compare the efficiency of various bottom mirror structures using single or multilayer silicon/silica stacks. We show then that this wafer-bonding compatible design increases the fibre grating coupler efficiency from 50% to more than 75%.
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Christophe Kopp, Tiphaine Dupont, Jean-Marc Fédéli, Régis Orobtchouk, "Silicon photonics: ready to wafer-bonding fibre grating coupler", Proc. SPIE 7606, Silicon Photonics V, 760618 (16 February 2010); doi: 10.1117/12.839679; https://doi.org/10.1117/12.839679
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