A. Delage

A Silicon-on-Insulator Photonic Wire Based Evanescent Field Sensor

We demonstrate a new, highly sensitive evanescent field sensor using silicon-on-insulator (SOI) photonic wire waveguides. Theoretical analysis shows that thin SOI waveguides can provide higher sensitivity over devices based in all other common planar waveguide material systems for the probing of both thin adsorbed biomolecular layers and bulk homogeneous solutions. A Si photonic wire waveguide was incorporated into a Mach-Zehnder interferometer based sensor, configured to monitor the index change of a homogeneous solution. High effective index change of 0.31 per refractive index unit (RIU) change of the solution was measured, confirming theoretical predictions

Planar waveguide echelle gratings in silica-on-silicon

Silica planar waveguide echelle grating demultiplexers with 48 channels and 256 channels are described and demonstrated. Polarization effects due to stress birefringence and polarization-dependent grating efficiency have been eliminated using a modified polarization compensator and grating design. The devices have a polarization-dependent wavelength shift of less than 10 pm, and a polarization-dependent loss below 0.2 dB. The 48-channel device has a measured crosstalk of -35 dB, an insertion loss better than 4 dB, and a uniformity of 1 dB across the C-band.

Integrated polarization compensator for WDM waveguide demultiplexers

An integrated polarization compensator for wavelength-division-multiplexed waveguide demultiplexers is proposed and experimentally demonstrated. It is simple to fabricate, has many advantages over previously reported polarization compensation schemes, and is effective in both etched diffraction grating and arrayed waveguide grating based devices.

Fractal Conductance Fluctuations in a Soft-Wall Stadium and a Sinai Billiard

Conductance fluctuations have been studied in a soft-wall stadium and a Sinai billiard defined by electrostatic gates on a high mobility semiconductor heterojunction. These reproducible magnetoconductance fluctuations are found to be fractal, confirming recent theoretical predictions of quantum signatures in classically mixed (regular and chaotic) systems. The fractal character of the fluctuations provides direct evidence for a hierarchical phase space structure at the boundary between regular and chaotic motion.

A broad-band waveguide grating coupler with a subwavelength grating mirror

A new diffractive device for light coupling between a planar optical waveguide and free space is proposed. The device utilizes a second-order waveguide grating to diffract the fundamental waveguide mode into two free propagating beams and a subwavelength grating (SWG) mirror to combine the two free propagating beams into a single beam. The finite-difference time-domain (FDTD) simulations show that the SWG mirror improves the coupling efficiency of the waveguide fundamental mode into the single out-coupled beam from about 30% to 92%. A high efficiency (>90%) is predicted for a broad wavelength range of 1520-1580nm. The proposed device is compact (/spl sim/80 /spl mu/m in length) and it eliminates the need for blazing the waveguide grating.

Correlation of Scattering Loss, Sidewall Roughness and Waveguide Width in Silicon-on-Insulator (SOI) Ridge Waveguides

We use star couplers to measure the relative scattering losses of silicon-on-insulator (SOI) ridge waveguides of various widths over the range of 1.75 to 0.2 mum in a single measurement. The scattering loss data obtained for waveguides fabricated by different photolithography and e-beam base processes correlate well with the measured root-mean-square roughness of the waveguide sidewalls obtained using SEM image analysis, and are in qualitative agreement with the prediction of simple scattering loss theory.

Arrayed waveguide grating demultiplexers in silicon-on-insulator

This paper presents theoretical and experimental results detailing the design and performance of arrayed waveguide grating (AWG) demultiplexers fabricated in silicon-on- insulator (SOI). The SOI waveguide is inherently multimode because of the high refractive index difference between Si and SiO2, although appropriate tailoring of the rib width to height ratio can be used to make single mode rib waveguides. This single mode condition cannot be met in the input and output combiner sections, which can therefore support many higher order modes. Modeling results demonstrate that coupling from a single mode ridge waveguide to the fundamental slab mode is typically two orders of magnitude larger than the coupling to higher modes. Hence the effect of multimode combiners on performance should be minimal. We also present calculations of bending losses which indicate that with a Si thickness of 1.5 micrometers , single mode rib waveguides can be made with radii of curvature as low as 200 micrometers . Such waveguides can also be made with zero birefringence. AWG devices were fabricated with 8 channels centered around (lambda) equals 1550 nm, and chip sizes less than 5 X 5 mm. The performance of these devices is compared with our modeling results.

Novel architecture for design of planar lightwave interleavers

This paper reports a novel architecture for the design of dense wavelength-division multiplexing interleavers based on planar echelle gratings. Double astigmatic point design of the echelle grating is discussed. The important and inherent limitation of aberrations associated with the echelle grating has been eliminated by the introduction of aberration free elliptical facets. A mechanism for compensating the variations of the refractive index with wavelength is also described. The theoretical analysis was used to design and manufacture remarkably low footprint 50/100 and 100/200 GHz interleavers in silica-on-silicon with the waveguide refractive index contrast of 0.62%. The comparison between the theoretical and experimental results shows an excellent agreement. The fabricated devices based on the proposed approach showed low nonuniformity in insertion loss, high dynamic range, and precise channel periodicity over the entire C band.

Wavelength-Dependent Model of a Ring Resonator Sensor Excited by a Directional Coupler

The spectral characteristics of a ring resonator made of Si photonic wires are modeled using mode expansion of supermodes of the directional coupler. The influence of the coupling coefficient, loss factor and waveguide dispersion on the spectral features are analyzed in detail. The model is then compared with the experimental data of a ring resonator designed for sensing purposes. The model that includes a wavelength dependence on coupling length reproduces the large variations of the envelope of the experimental spectrum, when coupling coefficient cover its full range from 0 to 1. Fitting parameters explain the details of the experimental spectrum and contribute to the sensor optimization, as well as illustrating general guidelines for ring resonator design.

Gating demultiplexer integrated with MSM detector array in InGaAs/AlGaAs/GaAs for WDM

The authors demonstrate the integration of a grating demultiplexer with curved output waveguides and a MSM photodetector array in InGaAs/AlGaAs/GaAs operating in the 1- mu m wavelength region. The structure provides 38 channels with 1-nm channel spacing. The total loss, including scattering from the unmetallized grating, is about 17 dB. A channel crosstalk of -11 dB is obtained. The FWHM of the channel pass band is 0.5 nm.<<ETX>>