Modelling of photonic wire Bragg Gratings

Some important properties of photonic wire Bragg grating structures have been investigate. The design, obtained as a generalisation of the full-width gap grating, has been modelled using 3D finite-difference time-domain simulations. Different types of stop-band have been observed. The impact of the grating geometry on the lowest order (longest wavelength) stop-band has been investigated - and has identified deeply indented configurations where reduction of the stop-bandwidth and of the reflectivity occurred. Our computational results have been substantially validated by an experimental demonstration of the fundamental stop-band of photonic wire Bragg gratings fabricated on silicon-on-insulator material. The accuracy of two distinct 2D computational models based on the effective index method has also been studied - because of their inherently much greater rapidity and consequent utility for approximate initial designs. A 2D plan-view model has been found to reproduce a large part of the essential features of the spectral response of full 3D models

Simulations of waveguide Bragg grating filters based on subwavelength grating waveguide

Subwavelength grating waveguides represent a flexible and perspective alternative to standard silicon-on-insulator nanophotonic waveguides. In such structures, waves propagate in the form of Bloch modes, in contrast to standard longitudinally uniform waveguides. Tunability of parameters of subwavelength grating structures possesses a great advantage of a broad variability of the (effective) refractive index and its dispersion, without significantly increasing fabrication complexity. A subwavelength grating structure is based on a (quasi)-periodic arrangement of two different materials, i.e. rectangular nanoblocks of silicon, embedded into a lower-index superstrate, with a period (much) smaller than the operational wavelength of the optical radiation. Clearly, by changing the filling factor, i.e., the duty-cycle of the subwavelength grating structure, its effective refractive index can be varied essentially between that of the superstrate and that of silicon. Our contribution is devoted to a detailed numerical analysis of Bloch modes in subwavelength grating waveguides and Bragg gratings based on subwavelength grating waveguides. Two independent versions of 3D Fourier modal methods developed within last years in our laboratories are used as our standard numerical tools. By comparison with results obtained with a 2D FDTD commercially available method we show that for reliable design of subwavelength grating waveguide devices of this kind, full-vector 3D methods have to be used. It is especially the case of Bragg gratings based on subwavelength grating waveguides, as analyzed in this paper. We discuss two options of a subwavelength grating modulation-designed by changing the subwavelength grating duty cycle, and by misplacement of Si blocks, and compare their properties from the point of view of fabrication feasibility

Waveguide sub-wavelength structures: a review of principles and applications

Periodic structures with a sub-wavelength pitch have been known since Hertz conducted his first experiments on the polarization of electromagnetic waves. While the use of these structures in waveguide optics was proposed in the 1990s, it has been with the more recent developments of silicon photonics and high-precision lithography techniques that sub-wavelength structures have found widespread application in the field of photonics. This review first provides an introduction to the physics of sub-wavelength structures. An overview of the applications of sub-wavelength structures is then given including: anti-reflective coatings, polarization rotators, high-efficiency fiber-chip couplers, spectrometers, high-reflectivity mirrors, athermal waveguides, multimode interference couplers, and dispersion engineered, ultra-broadband waveguide couplers among others. Particular attention is paid to providing insight into the design strategies for these devices. The concluding remarks provide an outlook on the future development of sub-wavelength structures and their impact in photonics.Peer reviewed: YesNRC publication: Ye

Enhanced sensitivity subwavelength grating waveguides for silicon photonics sensing applications

In this work we will review the enormous potential of subwavelength grating waveguides for sensing applications in the near and mid-infrared bands, demonstrating the capability to engineer the mode profile to maximize the light-matter interaction

High performance silicon photonic devices based on practical metamaterials

Subwavelength grating metamaterials are enabling a new generation of high-performance silicon photonic devices. Here we discuss the fundamental physics along with some of the latest advances in this rapidly expanding field

Subwavelength waveguide structures for optical interconnects

We report our advances in development of subwavelength engineered waveguide structures. This unique NRC patented technology [1,2] allows synthesis of a metamaterial with an unprecedented control of material properties, constituting a powerful tool for a designer of photonic integrated circuits. We have demonstrated a number of subwavelength engineered devices operating at telecom wavelengths [3-7], for example fibre-chip couplers, waveguide crossings, WDM multiplexers, ultra-fast optical switches, athermal waveguides, evanescent field sensors, polarization rotators, transceiver hybrids and ultra-broadband interference couplers. The subwavelength metamaterial concept has been adopted by industry (IBM) for fibre-chip coupling and subwavelength structures are likely to become key building blocks for the next generation of integrated photonic circuits. Here we present an overview of recent examples of our subwavelength engineered structures, with an emphasis on couplers for optical interconnects and evanescent field sensors. We demonstrate an unprecedented control over the light coupling between optical fibers and silicon chips by constructing metamaterial couplers operating at telecom (1.55 μm) and datacom (1.3 μm) wavelengths. We also show that by subwavelength patterning of silicon-wire waveguides the field delocalization can be engineered to increase the sensitivity of evanescent field waveguide sensors [8]. Finally, we discuss some emerging applications of subwavelength engineered structures in mid-infrared photonics