Low-loss, wide-band grating coupler and method of making same
View Patent ↗A method for fabricating a grating coupler having a bottom mirror in a semiconductor wafer including etching a trench from a top surface of a wafer and around a grating coupler formed in the wafer; etching a void underneath the grating coupler; etching a via into the void from the backside of the wafer; and depositing a mirror on the bottom of the grating coupler. Alternatively, additional oxide may be deposited on the bottom of the grating coupler prior to the deposition of the mirror such that a desirable oxide thickness on the bottom is achieved.
1. A method for preparing a low-loss, wide-band grating coupler comprising the steps of:
providing a optical grating disposed upon a top-surface of a substrate, wherein said optical grating including an overlying and underlying oxide cladding;
etching into the top surface of the substrate one or more trenches adjacent to the optical grating such that the trench extends into the substrate;
etching, by way of the one or more trenches, an undercut region beneath the optical grating in the substrate;
etching a via through a bottom surface of the substrate into the undercut region such that the underlying oxide cladding is exposed and accessible from the via; and
depositing a mirror onto the exposed underlying cladding.
2. The method according to claim 1 further comprising the step of depositing additional oxide to the underlying cladding such that a desired overall, underlying oxide thickness is achieved.
3. The method according to claim 2 wherein said mirror is one selected from the group consisting of: metal, or dielectric stack.
4. A method for preparing a low-loss, wide-band grating coupler comprising the steps of:
providing a optical grating disposed upon a substrate, wherein said optical grating including an overlying and underlying oxide cladding;
etching one or more trenches adjacent to the optical grating such that the trench extends into the substrate;
wet etching the one or more trenches such that an undercut region is etched beneath the optical grating in the substrate;
etching a via through a bottom of the substrate into the undercut region such that the underlying oxide cladding is exposed and accessible from the via; and
depositing a mirror onto the exposed underlying cladding.
5. The method according to claim 4 further comprising the step of depositing additional oxide to the underlying cladding such that a desired overall, underlying oxide thickness is achieved.
6. The method according to claim 5 wherein said mirror is one selected from the group consisting of: metal, or dielectric stack.