Quantum Cascade Lasers operating between 5.7 and 5.9 μm have been integrated on to a Germanium-on-Silicon (GoS) platform by flip-chip bonding. Sensing in this wavelength region is useful for a wide range of applications from monitoring caffeine and sweeteners, to analysis of oestrogen composition, which plays an important role in the metastatic spread of breast cancer. The approach demonstrated here uses laser bars incorporating twenty-four separate laser sources. Further enhancements of this system from the first generation are presented, including real-time power monitoring of the QCL output via fibrecoupling, more efficient gratings, improved support-structures and process improvements for both the QCL and GoS.
We review our recent results on modulators and detectors for the 2μm range, which may become very relevant for future communications, and on the development of mid-IR broadband devices for sensing applications. We show Mach-Zehnder and Michelson based modulators operating at data rates up to 25 Gb/s and Ge based detectors operating up to 12.5 Gb/s. For longer wavelengths relevant for sensing applications, we present broadband waveguides and splitters, waveguide integrated bolometers, and the realisation of a mid-infrared sensor.
Presentation: "Suspended silicon waveguide devices for mid-infrared sensing undefined" for the Emerging Applications in Silicon Photonics conference of the SPIE Photonex and Vacuum Expo 2020
Germanium has become a material of high interest for mid-infrared (MIR) integrated photonics due to its complementary metal-oxide-semiconductor (CMOS) compatibility and its wide transparency window covering the 2-15 μm spectral region exceeding the 4 μm and 8 μm limit of the Silicon-on-Insulator (SOI) platform and Si material respectively. Here, we present suspended germanium waveguides operating at wavelengths of 3.8 μm and 7.67 μm with propagation losses of 2.9 ± 0.2 dB/cm and 2.6 ± 0.3 dB/cm respectively.
In this paper we present silicon and germanium-based material platforms for the mid-infrared wavelength region and we report several active and passive devices realised in these materials. We particularly focus on devices and circuits for wavelengths longer than 7 micrometers.
Group IV platforms can operate at longer wavelengths due to their low material losses. By combining graphene and Si and Ge platforms, photodetection can be achieved by using graphene’s optical properties and coplanar integration methods. Here, we presented a waveguide coupled graphene photodetector operating at a wavelength of 3.8 μm.
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