P. Pottier

Quasi-one-dimensional photonic crystal as a compact building-block for refractometric optical sensors

We report the fabrication and the characterization of the refractometric and thermo-optical properties of a quasi-one-dimensional waveguide photonic crystal-a strong, 76-/spl mu/m-long Bragg grating. The transmission spectra (around 660 nm) of the structure have been measured as a function of both the cladding refractive index and the temperature. The transmission stopband was found to shift by 0.8-nm wavelength for either a cladding refractive index change of 0.05 or a temperature change of 120 K. The steep stopband edges provide a sensitive detection method for this band shift, by monitoring the transmitted output power.

Efficient coupling into slow-light photonic crystal channel guides using photonic crystal tapers.

Photonic crystal tapers have been designed for coupling of light from ridge waveguides into low group velocity photonic crystal channel guides. The coupling efficiency is increased from 3 % (case of butt-coupling) to 97 % for frequencies in the band-edge region, corresponding to a group index close to 100, as predicted using 2D finite-difference time-domain simulations.

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%.

Power and polarization beam-splitters, mirrors, and integrated interferometers based on air-hole photonic crystals and lateral large index-contrast waveguides.

Air hole 2D photonic crystals (PhC) and air slots have been used in association with semiconductor ridge waveguides to produce highly compact beam-splitters (less than 10 microm x10 microm) for power or polarization separators and mirrors. An efficiency of 99 % (in both 2D and 3D formulations) has been obtained for the power beam-splitter using finite-difference time-domain (FDTD) simulations - and around 95 % has been measured experimentally for structures realized in silicon-on-insulator (SOI) waveguides. In the polarization splitter, an extinction ratio as large as 11 dB was also reached experimentally. Examples of combinations of these elements in the form of interferometers are also presented.

Engineering the filter response of photonic crystal microcavity filters

Compact photonic crystal (PhC) filters will play a vital role in wavelength division multiplexing applications and they could be the stepping stones towards the realisation of dense and multifunctional photonic integrated circuits. Bragg grating concepts are applied to PhC filters to control their response by introducing suitable phase shifts and choosing appropriate locations and magnitudes. Moreover, the variation of the PhC hole size at the input and output regions could offer an extra degree of freedom in tailoring the filter characteristics. The ability to engineer and control the filter response of photonic crystal filters is investigated in this paper.

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.

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.

Effect of lithography stitching errors on Silicon-on-Insulator photonic wires

Electron beam lithography (EBL) is a widely used tool in the patterning of photonic integrated circuits, either by direct writing or by UV lithography with e-beam defined masks. It provides the benefit of pattern flexibility, high accuracy and the required nanometre-scale resolution.