Abstract
In this paper we review our recent results on group IV mid-infrared photonic devices. In particular, passive structures suitable for long wavelength operation, such as suspended Si, Ge-on-Si and suspended Ge, are analyzed. In addition, Ge-on-insulator waveguides have been characterized at 3.8 μm. Several active devices have been also realized: optical modulators in silicon and germanium, and silicon and graphene detectors operating at shorter mid-IR wavelengths.
Highlights
Group IV materials, such as Si, Ge, SiN, GeSn and graphene all have attractive properties for applications in the mid-IR
We report new results on optical modulators in Si and Ge at various wavelengths and graphene mid-IR detectors realized on the SOI platform, and give a brief review on recently published results on defect mediated Si detectors
The GOI samples reported here have been fabricated as described in [39]: a SiO2 capping layer was deposited on a bulk Ge wafer for protection; H+ ions were implanted under the Ge surface and the SiO2 layer removed; a 10 nm Al2O3 layer was deposited on the Ge surface; the Ge wafer was bonded to a Si wafer with 2 m SiO2 layer on the Si surface; the wafer was annealed to cause splitting along the implanted H+ ions; the wafer underwent a chemical mechanical polishing (CMP) process to reduce the Ge surface roughness
Summary
Group IV materials, such as Si, Ge, SiN, GeSn and graphene all have attractive properties for applications in the mid-IR. This demonstration was very promising and by adapting it for longer wavelengths we have recently fabricated suspended Si waveguides and bends operating at 7.7 m using a thicker SOI platform (1.4 m compared to 500 nm SOI from [28]) This time, the propagation loss was higher, 3.1 dB/cm [29], we estimated that 2.1 dB/cm came from the intrinsic material absorption of Si at 7.7 m, meaning that the loss related to scattering was ~1 dB/cm. This loss is very similar to the loss of chalcogenide [30] and GOS waveguides at the same wavelength After this first demonstration of a low loss Si waveguide operating at such a long wavelength, our future work will involve development of other passive devices for ~8 m and implementation of the platform for sensing as it can enable higher interaction between the evanescent optical mode and an analyte
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