Tunable optical filter with heater on a CTE-matched transparent substrate
View Patent ↗An optical device including: a glass substrate; a crystalline silicon layer bonded to the glass substrate; and a thermally tunable thin-film optical filter fabricated on top of the crystalline silicon layer.
1. An optical device comprising:
a glass substrate;
a doped single-crystal silicon sheet-resistive heater layer bonded to the glass substrate; and
a thermally tunable thin-film optical filter fabricated on top of the doped single-crystal silicon sheet-resistive heater layer, the thermally tunable thin-film optical filter comprising at least one amorphous semiconductor layer, and having a coefficient of thermal expansion approximately matched to a coefficient of thermal expansion of the glass substrate.
2. The optical device of claim 1 , wherein the optical filter is designed to operate on an optical signal of wavelength λ and wherein the glass substrate is transparent to light of wavelength λ.
3. The optical device of claim 2 , wherein the thermally tunable optical filter is a thermo-optically tunable thin film optical filter.
4. The optical device of claim 1 further comprising electrical contacts formed on the doped single-crystal silicon sheet-resistive heater layer for supplying electrical current to the doped single-crystal silicon sheet-resistive heater layer.
5. The optical device of claim 1 , wherein the glass substrate is made of a borosilicate glass.
6. The optical device of claim 1 , wherein the amorphous semiconductor is amorphous silicon.
7. The optical device of claim 1 , wherein the thermally tunable thin film optical filter comprises a plurality of thin film interference layers.
8. The optical device of claim 7 , wherein the optical filter is designed to operate on an optical signal of wavelength λ and wherein each of the layers among the plurality of thin film layers has an optical thickness that is roughly an integer multiple of λ/4.
9. The optical device of claim 1 , wherein the thermally tunable thin film optical filter comprises a stack of multiple Fabry-Perot cavities.
10. A method of making an optical device, the method comprising:
providing a glass substrate;
bonding a doped single-crystal silicon sheet-resistive heater layer to the glass substrate; and
fabricating a thermally tunable thin-film optical filter comprising at least one amorphous semiconductor layer on top of the doped single-crystal silicon sheet-resistive heater layer, the thermally tunable thin-film optical filter having a coefficient of thermal expansion approximately matched to a coefficient of thermal expansion of the class substrate.
11. The method of claim 10 , further comprising fabricating electrical contacts on the doped single-crystal silicon sheet-resistive heater layer for supplying electrical current to the heater layer.
12. The method of claim 10 further comprising, prior to fabricating the optical filter, patterning the doped single-crystal silicon sheet-resistive heater layer to form an island on which the optical filter is fabricated.
13. The method of claim 10 , wherein the doped single-crystal silicon sheet-resistive heater layer is anodically bonded to the glass substrate.
14. The method of claim 10 , wherein the fabricating the thermally tunable thin-film optical filter on top of the doped single-crystal silicon sheet-resistive heater layer involves fabricating a thermo-optically tunable thin film, optical filter.