We present the realization of an optical sensor based on an infiltrated high-$Q$ slot photonic crystal cavity in a nonfreestanding membrane configuration. Successive infiltrations by liquids with refractive indices ranging from 1.345 to 1.545 yield a sensitivity $S$ of 235 nm/RIU (refractive index unit), while the $Q$-factor is comprised between 8000 and 25,000, giving a sensor figure of merit up to 3700. This sensor has a detection limit of $1.25\times {10}^{-5}$. The operation of this device on a silicon-on-insulator (SOI) substrate allows a straightforward integration in the silicon photonics platform, while providing a compliant mechanical stability.

The use in silicon photonics of the new optical materials developed in soft matter science (e.g. polymers, liquids) is delicate because their low refractive index weakens the confinement of light and prevents an efficient control of the dispersion properties through the geometry. We experimentally demonstrate that such materials can be incorporated in 700 μm long slot photonic crystal waveguides and hence can benefit from both slow-light field enhancement effect and slot-induced ultra-small effective areas. Additionally, we show that their dispersion can be engineered from anomalous to normal regions, along with the presence of multiple zero group velocity dispersion (ZGVD) points exhibiting Normalized Delay Bandwidth Product as high as 0.156. The reported results provide experimental evidence for an accurate control of the dispersion properties of fillable periodical slotted structures in silicon photonics, which is of direct interest for on-chip all-optical data treatment using nonlinear optical effects in hybrid-on-silicon technologies.

We experimentally investigate refractive index sensing in silicon slot waveguide ring resonators by the detection of the giant shift of the ring transmission spectrum envelope enabled by the following specific conditions: the slot waveguide cross section as well as the ring couplers have been designed to lead to a V-shaped microring resonator spectrum modulated by the classical frequency comb and exhibiting quality factor peaks of 2000–6000 around $\lambda =1.5\mathrm{\mu m}$. By tracking the spectrum envelope wavelength shift, sensitivity up to $S=1,300\mathrm{nm}$ per refraction index unit (RIU) is reported when the slots are filled by liquids with refraction index values close to 1.33.

In this paper, we report the experimental characterization of highly nonlinear GeSbS chalcogenide glass waveguides. We used a single-beam characterization protocol that accounts for the magnitude and sign of the real and imaginary parts of the third-order nonlinear susceptibility of integrated ${\mathrm{Ge}}_{23}{\mathrm{Sb}}_7{\mathrm{S}}_{70}$ (GeSbS) chalcogenide glass waveguides in the near-infrared wavelength range at $\lambda =1580\mathrm{nm}$. We measured a waveguide nonlinear parameter of $7.0\pm 0.7{\mathrm{W}}^{-1}·{\mathrm{m}}^{-1}$, which corresponds to a nonlinear refractive index of $n_2=(0.93\pm 0.08)\times {10}^{-18}{\mathrm{m}}^2/\mathrm{W}$, comparable to that of silicon, but with an 80 times lower two-photon absorption coefficient ${\beta }_{\mathrm{TPA}}=(0.010\pm 0.003)\mathrm{cm}/\mathrm{GW}$, accompanied with linear propagation losses as low as 0.5 dB/cm. The outstanding linear and nonlinear properties of GeSbS, with a measured nonlinear figure of merit ${\mathrm{FOM}}_{\mathrm{TPA}}=6.0\pm 1.4$ at $\lambda =1580\mathrm{nm}$, ultimately make it one of the most promising integrated platforms for the realization of nonlinear functionalities.

Silicon photonics is a large volume and large scale integration platform for applications from long-haul optical telecommunications to intra-chip interconnects. Extension to the mid-IR wavelength range is now largely investigated, mainly driven by absorption spectroscopy applications. Germanium (Ge) is particularly compelling as it has a broad transparency window up to 15 µm and a much higher third-order nonlinear coefficient than silicon which is very promising for the demonstration of efficient non-linear optics based active devices. Si_1−xGe_x alloys have been recently studied due to their ability to fine-tune the bandgap and refractive index. The material nonlinearities are very sensitive to any modification of the energy bands, so Si_1−xGe_x alloys are particularly interesting for nonlinear device engineering. We report on the first third order nonlinear experimental characterization of Ge-rich Si_1−xGe_x waveguides, with Ge concentrations x ranging from 0.7 to 0.9. The characterization performed at 1580 nm is compared with theoretical models and a discussion about the prediction of the nonlinear properties in the mid-IR is introduced. These results will provide helpful insights to assist the design of nonlinear integrated optical based devices in both the near- and mid-IR wavelength ranges.

We demonstrated a class of highly nonlinear hybrid waveguide structures based on infiltration of ${\mathrm{As}}_2{\mathrm{S}}_3$ chalcogenide glass into silicon slot waveguides. The nonlinear properties of the hybrid waveguides were precisely quantified via a bidirectional top-hat D-scan method, enabling a direct comparison between properties measured using different device geometries. We experimentally demonstrate hybrid ${\mathrm{As}}_2{\mathrm{S}}_3$-Si slot waveguides with a two-photon absorption (TPA) figure of merit exceeding 2 at near infrared wavelengths. These waveguides largely satisfy the critical criterion for efficient nonlinear integrated photonics (${\mathrm{FOM}}_{\mathrm{TPA}}^{wg}>1$), allowing phase shifts greater than $\pi$ with minimal overall losses. These results pave the way for efficient and robust ultrafast all-optical devices and circuits in large-scale silicon photonics technology.