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Advanced photonic probes are important for the development of non-contact wafer-scale testing of photonic chips. Here, Vynck et al. develop a quantitative technique based on mapping of transmittance variations by ultrafast perturbations to analyze arbitrary linear multi-port photonic devices.

Integrated optical circuits today are typically designed for a few special functionalities and require complex design and development procedures. Here, the authors demonstrate a reconfigurable but simple silicon waveguide mesh with different functionalities.

Abstract Nonlinear silicon photonic devices have attracted considerable attention thanks to their ability to show large third-order nonlinear effects at moderate power levels allowing for all-optical signal processing functionalities in miniaturized components. Although significant efforts have been made and many nonlinear optical functions have already been demonstrated in this platform, the performance of nonlinear silicon photonic devices remains fundamentally limited at the telecom wavelength region due to the two photon absorption (TPA) and related effects. In this work, we propose an alternative CMOS-compatible platform, based on silicon-rich silicon nitride that can overcome this limitation. By carefully selecting the material deposition parameters, we show that both of the device linear and nonlinear properties can be tuned in order to exhibit the desired behaviour at the selected wavelength region. A rigorous and systematic fabrication and characterization campaign of different material compositions is presented, enabling us to demonstrate TPA-free CMOS-compatible waveguides with low linear loss (~1.5 dB/cm) and enhanced Kerr nonlinear response (Re{γ} = 16 Wm−1). Thanks to these properties, our nonlinear waveguides are able to produce a π nonlinear phase shift, paving the way for the development of practical devices for future optical communication applications.

In this paper, we propose a generalized procedure for the design of integrated Vernier devices for high performance chemical and biochemical sensing. In particular, we demonstrate the accurate control of the most critical design and fabrication parameters of silicon-on-insulator cascade-coupled racetrack resonators operating in the second regime of the Vernier effect, around 1.55 μm. The experimental implementation of our design strategies has allowed a rigorous and reliable investigation of the influence of racetrack resonator and directional coupler dimensions as well as of waveguide process variability on the operation of Vernier devices. Figures of merit of our Vernier architectures have been measured experimentally, evidencing a high reproducibility and a very good agreement with the theoretical predictions, as also confirmed by relative errors even lower than 1%. Finally, a Vernier gain as high as 30.3, average insertion loss of 2.1 dB and extinction ratio up to 30 dB have been achieved.

Hydrogel materials offer many advantages for chemical and biological sensoring due to their response to a small change in their environment with a related change in volume. Several designs have been outlined in the literature in the specific field of hydrogel-based optical sensors, reporting a large number of steps for their fabrication. In this work we present a three-dimensional, hydrogel-based sensor the structure of which is fabricated in a single step using thermal nanoimprint lithography. The sensor is based on a waveguide with a grating readout section. A specific hydrogel formulation, based on a combination of PEGDMA (Poly(Ethylene Glycol DiMethAcrylate)), NIPAAm (N-IsoPropylAcrylAmide), and AA (Acrylic Acid), was developed. This stimulus-responsive hydrogel is sensitive to pH and to water. Moreover, the hydrogel has been modified to be suitable for fabrication by thermal nanoimprint lithography. Once stimulated, the hydrogel-based sensor changes its topography, which is characterised physically by AFM and SEM, and optically using a specific optical set-up.

Change History: A correction to this article has been published and is linked from the HTML version of this article.

In this paper we demonstrate the ability to fabricate fishnets by nanoimprinting directly into a pre-deposited three layer metal–dielectric–metal stack, enabling us to pattern large areas in two minutes. We have designed and fabricated two different fishnet structures of varying dimensions using this method and measured their resonant wavelengths in the near-infrared at 1.45 μ m and 1.88 μ m. An important by-product of directly imprinting into the metal–dielectric stack, without separation from the substrate, is the formation of rectangular nanopillars that sit within the rectangular apertures between the fishnet slabs. Simulations complement our measurements and suggest a negative refractive index real part with a magnitude of 1.6. Further simulations suggest that if the fishnet were to be detached from the supporting substrate a refractive index real part of 5 and FOM of 2.74 could be obtained.

SiNx layers intended for photonic applications are typically fabricated using LPCVD and PECVD. These techniques rely on high-temperature processing (>400 °C) to obtain low propagation losses. An alternative version of PECVD SiNx layers deposited at temperatures below 400 °C with a recipe that does not use ammonia (NH3-free PECVD) was previously demonstrated to be a good option to fabricate strip waveguides with propagation losses   <3 dB cm−1. We have conducted a systematic investigation of the influence of the deposition parameters on the material and optical properties of NH3-free PECVD SiNx layers fabricated at 350 °C using a design of experiments methodology. In particular, this paper discusses the effect of the SiH4 flow, RF power, chamber pressure and substrate on the structure, uniformity, roughness, deposition rate, refractive index, chemical composition, bond structure and H content of NH3-free PECVD SiNx layers. The results show that the properties and the propagation losses of the studied SiNx layers depend entirely on their compositional N/Si ratio, which is in fact the only parameter that can be directly tuned using the deposition parameters along with the film uniformity and deposition rate. These observations provide the means to optimise the propagation losses of the layers for photonic applications through the deposition parameters. In fact, we have been able to fabricate SiNx waveguides with H content  <20%, good uniformity and propagation losses of 1.5 dB cm−1 at 1550 nm and   <1 dB cm−1 at 1310 nm. As a result, this study can potentially help optimise the properties of the studied SiNx layers for different applications. [ABSTRACT FROM AUTHOR]

We demonstrate low-loss slot waveguides on silicon-on-insulator (SOI) platform. Waveguides oriented along the (11-2) direction on the Si (110) plane were first fabricated by a standard e-beam lithography and dry etching process. A TMAH based anisotropic wet etching technique was then used to remove any residual side wall roughness. Using this fabrication technique propagation loss as low as 3.7dB/cm was realized in silicon slot waveguide for wavelengths near 1550nm. We also realized low propagation loss of 1dB/cm for silicon strip waveguides.