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Slot waveguides are becoming more and more attractive optical components, especially for chemical and bio-chemical sensing. In this paper an accurate analysis of slot waveguide fabrication tolerances is carried out, in order to find optimum design criteria for either homogeneous or absorption sensing mechanisms, in cases of low and high aspect ratio slot waveguides. In particular, we have focused on Silicon On Insulator (SOI) technology, representing the most popular technology for this kind of devices, simultaneously achieving high integration capabilities, small dimensions and low cost. An accurate analysis of single mode behavior for high aspect ratio slot waveguide has been also performed, in order to provide geometric limits for waveguide design purposes. Finally, the problem of coupling into a slot waveguide is addressed and a very compact and efficient slot coupler is proposed, whose geometry has been optimized to give a strip-slot-strip coupling efficiency close to 100%. [ABSTRACT FROM AUTHOR]

Scattering loss in high-index-contrast optical waveguides has been modeled by a rigorous 3D numerical algorithm based on volume current method. The electromagnetic field generated by the wire current distribution simulating sidewalls roughness has been calculated by 3D finite element method. The developed modeling technique does not introduce any approximation in radiated power estimation. Numerical results obtained by our model have been compared with some experimental results reported in literature for four typical sub-micrometer high-index-contrast waveguides realized by different technologies and a very good agreement (relative error less than 3%) has been demonstrated. Closed-form expressions for scattering loss in low-index-contrast waveguides have been also derived and discussed. Developed modeling technique has been compared with other three-dimensional algorithms for scattering loss estimation and its advantages in terms of accuracy, computation time and generality have been pointed out. Scattering loss dependence on the parameters of the roughness distribution has been finally discussed. [ABSTRACT FROM AUTHOR]

In this paper the numerical modeling of periodic structures for implementation of a novel type of photonic sensors by using the 3D finite difference time domain (FDTD) method is presented. The sensing is based on the optical phenomena occurring in the segmented grating which is placed on the thin silica buffer over the silicon wire waveguide in the silicon‐on‐insulator (SOI) structure. This design provides the effective resonance interaction of the guided wave with the virtual leaky wave supported by the segmented grating evanescently coupled with the silicon wire. The dropping wavelength of this interaction is strongly dependent on the grating environment and it provides a strong refractometricsensitivity (Sn > 420 nm RIU−1) and surface sensitivity Sh > 0.17, evaluated in the case of water. The modeling proves that the effect of abnormal blocking due to virtual leaky wave could be the base for the design of optical sensors with extremely high sensitivity. 3D FDTD modeling is used to investigate the sensing properties in water of segmented gratings of SU‐8 polymer having period 1.4 µm and evanescently coupled with an underlying silicon wire. Sensor shows homogeneous sensitivity Sn = ∂λ/∂n > −420 nm‐1 and surface sensitivity Sh = ∂λ/∂h > 0.17. Its sensitivities are compatible with those of slot or subwavelength structures but using four times larger feature sizes. [ABSTRACT FROM AUTHOR]

The influence of high energy radiations on the performance of silicon-on-insulator photonic devices, such as straight waveguides, ring resonators and Raman lasers based on resonant microcavities, has been investigated theoretically in the near infrared. The modeling is based on a generalized full-vectorial wave equation system which also includes deep defect rate equations. Simulation results are compared with the state-of-the-art, demonstrating a very good agreement between theoretical predictions and experiments reported in literature in the case of both ionizing and nonionizing events. Moreover, a parametric analysis is presented in order to investigate the degradation mechanisms of photonic device performance that occur under the influence of radiation bombardment. [ABSTRACT FROM AUTHOR]

In this paper, a spectroscopic sensor formed by a silicon-on-insulator waveguiding Bragg grating ring resonator working in linear and non-linear regime is proposed. In linear regime, the device shows a spectral response characterized by a photonic band gap (PBG). Very close to the band gap edges, the resonant structure exhibits split modes having a splitting magnitude equal to the PBG spectral extension, whose characteristics can be exploited to obtain a RI optical sensor almost insensitive to the fabrication tolerances and environmental perturbations. When the device operates in nonlinear regime, exactly in the spectral region showing the split resonant modes, the RI sensing performance is strongly improved with respect to the linear regime. This improvement, demonstrated by taking into account all the non-linear effects excited in the integrated silicon structure (i.e., Two Photon Absorption (TPA), TPA-induced Free Carrier Absorption, plasma dispersion, Self-Phase-Modulation and Cross-Phase-Modulation effects as induced by Kerr nonlinearity) as well as the deleterious thermal and stress effects, allows enhancing the performance of the RI split mode resonant sensors, while achieving good immunity to the fabrication tolerances and environmental perturbations. The improvement in terms of sensor resolution can be at least one order of magnitude, still without using optimal parameters. [ABSTRACT FROM AUTHOR]