Iraklis Ntakis

Optimization of transmission properties of two-dimensional photonic crystal channel waveguide bends through local lattice deformation

We present an extended study of different topologies for lattice-deformed two-dimensional single line-defect (W1) photonic crystal channel waveguide bends and their effect on the optimization of the bend transmission properties. An enhancement of the spectral response by a factor of six was obtained, with the optimal design providing transmission greater than 95% over a 5.2% relative bandwidth. Experimental results for devices realized in III–V semiconductor epitaxial structure show a transmission efficiency of 95%.

Photonic crystal continuous taper for low-loss direct coupling into 2D photonic crystal channel waveguides and further device functionality

Abstract We present a novel kind of hole-based photonic crystal (PhC) taper. Based on continuous tapering and lattice distortion, this structure can transmit up to 98.4% of the incident light (computed value) for a beam reduction factor of 4:1 over a length of only 5 μm into a single row (W1) 2D PhC channel waveguide. The various properties of this taper are discussed. Experimental results for tapers realised in a III–V semiconductor epitaxial structure show that an insertion efficiency of 90% into a W1 PhC waveguide can be achieved.

Photonic crystal and photonic wire nano-photonics based on silicon-on-insulator

Silicon-on-insulator (SOI) is a strong candidate for application in future planar waveguide integration technology, whether or not luminescence is extracted from the silicon. We review recent research on photonic devices based on silicon-on-insulator. These devices exploit either photonic crystal or photonic wire concepts—or combinations of both. Aspects of the technologies used that are particularly critical for successful implementation of SOI-based photonics are addressed.

Photonic crystal waveguide Mach-Zehnder structures for thermo-optic switching

This paper highlights photonic crystal Mach-Zehnder structures that use W1 channel waveguide in 2D hexagonal photonic crystal structures and have channel orientation along GammaK directions. The FDTD software, Fullwave, from RSoft has been used to simulate photonic crystal channel waveguides, Y-junction and bend in order to design a complete Mach-Zehnder interferometer structure in epitaxial II-V semiconductor material for operation at 1550nm. It is our near-future aim to use these Mach-Zehnder structures as the basis for thermo-optic switching devices. Electro-Beam lithography (EBL) and reactive ion etching (dry-etching) processes have been used to fabricate these devices

Systematic investigation of misalignment effects at junctions between feeder waveguide and photonic crystal channel waveguide

Feature Issue on Nanoscale Integrated Photonics for Optical Networks The coupling between two different guiding elements, a ridge waveguide and a photonic crystal channel waveguide (obtained by a single line defect in the crystal), is investigated both computationally and experimentally. The study concentrates on the effects that different widths for the ridge waveguide, as well as positions with respect to the channel waveguide, have on the coupling efficiency--thus allowing the assessment of the sensitivity to drift effects that can occur in fabrication--and the optimal design parameters. Characterization of devices fabricated in GaAs/AlGaAs epitaxial waveguide material shows good overall agreement with the simulated trends for all the configurations of the junction considered. On the other hand, the trends from experiments also demonstrate reduced dependency of transmission on mismatch, by comparison with simulations. Finally, the configuration, which allows optimum coupling and transmission (98%), is found to be verified by both simulation and characterization.

Efficient transmission of 60/spl deg/ photonic-crystal bend by waveguide width tuning

Summary form only given. Photonic crystal (PhC) channel waveguides formed as single or multiple line defects have been investigated and, in the case of a lattice of air holes perforating a dielectric slab, even the single line defect PhC channel waveguides are multimoded. One method to tackle the problem in the case of waveguides with dielectric lateral confinement is to use low-Q cavity resonant effects as they have been shown to improve the performance of the junction(s). Our approach is targeted towards tuning the waveguide width at the region of the bend, because in this case, the modes of interest can be pushed closer to the mid-gap frequency. A two-dimensional finite-difference-time-domain (FDTD) tool is used in order to analyse the dependence of the transmission of the bend on the offset shift.

Photonic crystal and photonic wire device structures

Photonic devices that exploit photonic crystal (PhC) principles in a planar environment continue to provide a fertile field of research. 2D PhC based channel waveguides can provide both strong confinement and controlled dispersion behaviour. In conjunction with, for instance, various electro-optic, thermo-optic and other effects, a range of device functionality is accessible in very compact PhC channel-guide devices that offer the potential for high-density integration. Low enough propagation losses are now being obtained with photonic crystal channel-guide structures that their use in real applications has become plausible. Photonic wires (PhWs) can also provide strong confinement and low propagation losses. Bragg-gratings imposed on photonic wires can provide dispersion and frequency selection in device structures that are intrinsically simpler than 2D PhC channel guides--and can compete with them under realistic conditions.

Semiconductor-based active and passive nanophotonics

Nano-structured semiconductors will play a vital role in future photonics, providing efficient localised photon generation and various other functions for communications, sensing, imaging and display applications. We shall provide several illustrative examples of possibilities.

Photonic crystal and photonic wire technology, materials and devices

Light channeling and other structures that exploit strong optical confinement are an essential requirement for the realisation of high-density photonic integrated circuits. Strong confinement and controlled feedback are also important for efficient and compact sources for light with various levels of coherence and directionality. The presentation will survey work on various planar photonic crystal and wire device structures realised both in material systems providing strong vertical confinement (e.g. S-o-I) and in systems with weak vertical confinement such as typical epitaxial III-V semiconductor heterostructures. Work towards the combination of a number of elements into a single photonic IC will be highlighted, as will structures which combine photonic crystal and photonic wire features. Planar microcavities for frequency selection will be featured, in particular. We shall also resurvey briefly the technology aspects of fabrication, including electron-beam lithography (EBL), reactive ion etching (RIE), focused ion-beam etching (FIBS) and excimer laser lithography. Finally we shall consider techniques for the growth of self-organised photonic crystals with greater perfection and better controlled orientation.

Wide bandwidth transmission through a deformed-lattice photonic crystalchanne! waveguide Y-splitter.

We report an experimental realisation of a photonic crystal W1 channel waveguide Y-splitter. The device has been optimised through local laitice deformation in .fie junction region, pro. t.. iding efficient transmission over a broad spectrum.