Germanium-on-silicon platforms for nonlinear photonics in the mid-infrared

We review our progress in the characterization of the nonlinear transmission properties of low loss germanium-on-silicon waveguides. Simple pump-probe experiments are employed to demonstrate their use for all-optical control

Germanium-on-silicon platforms for nonlinear photonics in the mid-infrared

We review our progress in the characterization of the nonlinear transmission properties of low loss germanium-on-silicon waveguides. Simple pump-probe experiments are employed to demonstrate their use for all-optical control

All-optical modulation in germanium-on-silicon waveguides in the mid-infrared

All-optical modulation is demonstrated in low loss germanium-on-silicon waveguides at mid-infrared wavelengths. The results indicate the suitability of this platform for optical signal processing in this long wavelength regime

Suspended SOI waveguide with sub-wavelength grating cladding for mid-infrared

We present a new type of mid-infrared silicon-on-insulator (SOI) waveguide. The waveguide comprises a sub-wavelength lattice of holes acting as lateral cladding while at the same time allowing for the bottom oxide (BOX) removal by etching. The waveguide loss is determined at the wavelength of 3.8 µm for structures before and after being underetched using both vapor phase and liquid hydrofluoric acid (HF). A propagation loss of 3.4 dB/cm was measured for a design with a 300 nm grating period and 150 nm holes after partial removal (560 nm) of BOX by vapor phase HF etching. We also demonstrate an alternative design with 550 nm period and 450 nm holes, which allows a faster and complete removal of the BOX by liquid phase HF etching, yielding the waveguide propagation loss of 3.6 dB/cm

Two-photon absorption and all-optical modulation in germanium-on-silicon waveguides for the mid-infrared

The nonlinear absorption properties of a germanium-on-silicon waveguide have been characterized across the two-photon absorption (TPA) transmission window. The results show that the TPA parameters in germanium waveguides are much stronger than the peak values in silicon, in good agreement with selected measurements conducted in bulk materials. Exploiting the large nonlinear absorption near the bandedge, efficient all-optical modulation is achieved with a modulation depth of ~8dB and a response time <5ps.Currently under review

Mid-infrared all-optical modulation in low-loss germanium-on-silicon waveguides

All-optical modulation has been demonstrated in a germanium-on-silicon rib waveguide over the mid-infrared wavelength range of 2-3µm using a free-carrier absorption scheme. Transmission measurements have shown the waveguides to have low propagation losses that are relatively independent of wavelength out to 3.8µm, indicating that the modulation could be extended further into the mid-infrared region for applications in sensing and spectroscopy. By monitoring the material recovery, the free-carrier lifetime of the micron-sized waveguides has been estimated to be ~18ns, allowing for modulation speeds within the megahertz regime

Mid-infrared silicon waveguide-based bolometer

We demonstrate the first waveguide-based bolometers on Silicon-on-Insulator (SOI) platform for mid-infrared (MIR) wavelengths, which use plasmonic antennas as absorbing elements. The bolometer achieves a sensitivity of 0.80 % change in resistance per milliwatt of input power at the 3.8 µm wavelength