Design of the Bimodal Grating Sensor with a Built-In Mode Demultiplexer.

This new sensor design provides good volume sensitivity (around 1600 nm/RIU) via collinear diffraction by the asymmetric grating placed in the waveguide vicinity. It provides the mode transformation between the fundamental TE and the first TE modes of the silicon wire (0.22 μm by a 0.

Effect of Dispersion-Enhanced Sensitivity in a Two-Mode Optical Waveguide with an Asymmetric Diffraction Grating.

Analysis of trends in the development of silicon photonics shows the high efficiency regarding the creation of optical sensors. The concept of bimodal sensors, which suggests moving away from the usual paradigm based only on single-mode waveguides and using the inter-mode interaction of guided optical waves in a two-mode optical waveguide, is developed in the present paper. In this case, the interaction occurs in the presence of an asymmetric periodic perturbation of the refractive index above the waveguide surface.

Numerical Simulation of Optical Sensing by the Far Field Pattern Radiated by Periodic Grating Strips Over Silica Buffer on the Silicon Wire Waveguide.

This paper presents results of numerical modeling of a modified design of an optical sensor based on segmented periodic silicon oxynitride (SiON) grating evanescently coupled with silicon wire. This segmented grating works as a leaky waveguide, which filters input power from a broadband optical source and radiates it as an outcoming optical beam with both a small wavelength band and a small beam divergence. The radiation angle strongly depends on the refractive index of the grating environment and provides sensor interrogation by measuring the far field pattern in the focal plane of the lens, which is placed near the sensor element.

Numerical Simulation of a Novel Sensing Approach Based on Abnormal Blocking by Periodic Grating Strips near the Silicon Wire Waveguide.

This paper discusses the physical nature and the numerical modeling of a novel approach of periodic structures for applications as photonic sensors. The sensing is based on the high sensitivity to the cover index change of the notch wavelength. This sensitivity is due to the effect of abnormal blocking of the guided wave propagating along the silicon wire with periodic strips overhead it through the silica buffer.

Experimental demonstration of original optical filter based on multiply coupled waveguides.

We present an experimental demonstration of an optical filter based on multiply coupled waveguides that has previously been demonstrated only numerically. The experimental results show a good match to numerical modeling using a 2D finite-difference time-domain method that utilizes a modified effective index method (MEIM) approximation. The MEIM correctly describes both the phase and the group indices of 3D silicon wire, providing the means to study complicated and large photonic structures with moderate computer resources and simulation time.

Modified effective index method to fit the phase and group index of 3D photonic wire waveguide.

A modified effective index method (MEIM), which correctly describes, in a 2D case, both the phase and the group indexes in a 3D photonic wire waveguide, is introduced in the Letter. The MEIM utilizes the combined index profile with two spatial parameters. The central part with wire index has the width of nearly a wire height, and it is responsible for the group index.

Compact interrogator for fiber optic Bragg sensors based on an acousto-optic filter formed by photonic crystal rows of air holes.

Fiber optic sensors are typically used with expensive tunable lasers or optical spectrum analyzers for wavelength interrogation. We propose to replace the tunable laser by a broadband optical source incorporated with a novel thin linewidth acousto-optic tunable filter. It utilizes optical beam expanders constituted by photonic crystal rows of air holes in LiNbO(3) waveguide.

Efficient silicon wire waveguide crossing with negligible loss and crosstalk.

Multiple optical elements utilize crossing of channel optical waveguides. This paper introduces efficient silicon wire waveguide crossing by means of vertical coupling of tapered Si wire with upper polymer wide strip waveguide through a silica buffer. Numerical simulations by 3D FDTD prove that optimal structure of 70 µm length can provide 98% efficiency for through pass and 99.

Compact acousto-optic filter with beam expanders constituted by photonic crystal rows of airholes.

A compact acousto-optic (AO) filter with multireflector (MR) beam expanders constituted by 32 photonic crystal rows of airholes in LiNbO(3) waveguide has been proposed and numerically studied by the two-dimensional finite-difference-time-domain method. The diameter and position of every row of holes are gradually varied along MR beam expanders in order to provide high efficiency and good sidelobe suppression. Device sizes are 70 μm × 150 μm, with an FWHM bandwidth of 4.

Power beam splitter based on photonic crystal row of holes and Brewster effect in SOI waveguides.

This Letter presents a beam splitter in a silicon-on-insulator (SOI) ridge waveguide loaded by a photonic crystal row of holes close to the Brewster angle. The propagation of the fundamental guided mode in this structure has been examined by the three-dimensional finite-difference time-domain method. It is shown that a TE-polarized optical beam exhibits the Brewster effect at an incident angle of about 39 degrees, giving a small splitting ratio (<0.

New wide strip and grating loaded quasi-single-mode waveguide on SOI.

New wide single mode strip and grating loaded waveguide on thin silicon-on-insulator CMOS compatible structure is proposed and analyzed. Waveguide is built by silicon nitride strip and gratings placed on silica cover of slab silicon. This structure is similar to conventional strip-loaded waveguide but differs by additional gratings near the strip sides.

Optical properties of new wide heterogeneous waveguides with thermo optical shifters.

We present analysis and simulation of novel silicon-on-insulator (SOI) heterogeneous waveguides with thermo-optic phase shifters. New structure design contains a p-n junction on both sides of SOI ridge waveguide with 220 nm x 35 microm silicon core. Strongly mode-dependent optical losses (by additional free charge absorption) provide quasi-singe-mode behavior of wide waveguide with mode size approximately 10 microm.

Thin heterogeneous SOI waveguides for thermo-optical tuning and filtering.

This work presents an analysis and simulation of novel heterogeneous silicon-on-insulator (SOI) waveguide structures for reconfigurable optical add/drop multiplexers (ROADMs) with thermo-optic tuning and multi-reflector beam expanders. New structure design includes p(+) side-doping of SOI ridge waveguide with 220 nm x 16 microm silicon core. It provides quasi mono-mode behavior due to strongly mode-dependent optical losses by free charge absorption.

New compact polarization rotator in anisotropic LiNbO3 graded-index waveguide.

The new compact polarization rotator in anisotropic graded index Ti:LiNbO(3) channel waveguide is proposed and investigated by 3D beam propagation method (BPM). Device is based on a channel optical waveguide directed at small angle (about 5 degrees) with respect to Z-axis on Y-cut lithium niobate substrate. The polarization conversion from quasi-TE to quasi-TM guided modes (and backwards) along 8 mm long waveguide with an index contrast 0.

Investigation of thermo-optic effect and multi-reflector tunable filter/multiplexer in SOI waveguides.

The paper presents an analysis of thermo-optic phase shifters in silicon-on-insulator (SOI) waveguide structures. It gives recommendations to provide high tuning characteristics at minimum power requirements. Then, this analysis is applied to the description of a novel type of reconfigurable optical add/drop multiplexer (ROADM) utilizing multi-reflector (MR) beam expanders and thermo-optic tuning in SOI structures.