Andre Delage

Bio: Andre Delage is an academic researcher from National Research Council. The author has contributed to research in topics: Waveguide (optics) & Diffraction grating. The author has an hindex of 22, co-authored 141 publications receiving 1922 citations.

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

Abstract: 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 031 per refractive index unit (RIU) change of the solution was measured, confirming theoretical predictions

Monolithic integrated wavelength demultiplexer based on a waveguide Rowland circle grating in InGaAsP/lnP

Abstract: We present detailed modeling and experimental results for an improved design of an InGaAsP-InP wavelength demultiplexer based on a monolithically integrated Rowland circle grating. The design incorporated ten wavelength channels at 1.55 /spl mu/m with a uniform spacing of 2 nm. The total on-chip loss was about 10 dB and the crosstalk between adjacent channels was as low as -25 dB. It was shown that low-loss etched turning mirrors can reduce the total on-chip loss by about 4 dB compared to traditional 90/spl deg/ curved multimode waveguides. By replacing standard flat grating facets with retro-reflecting V-shaped facets in the echelle grating, the loss was further reduced by 4 dB. Polarization independent operation within a passband of 0.5 nm was achieved by using multimode output waveguides. The potential sources producing the crosstalk have been analyzed and fabrication modifications for further improvement are suggested.

Planar waveguide echelle gratings in silica-on-silicon

Abstract: 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.

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

Abstract: 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.

Mid-Infrared Silicon-on-Insulator Fourier-Transform Spectrometer Chip

Abstract: Mid-infrared absorption spectroscopy is highly relevant for a wide range of sensing applications. In this letter, we demonstrate a Fourier-transform spectrometer chip based on the principle of spatial heterodyning implemented in the silicon-on-insulator waveguide platform, and operating near 3.75- $\mu \text{m}$ wavelength. The spectrometer comprises a waveguide splitting tree feeding to an array of 42 Mach–Zehnder interferometers with linearly increasing optical path length differences. A spectral retrieval algorithm based on calibration matrices is applied to the stationary output pattern of the array, compensating for any phase and amplitude errors arising from fabrication imperfections. A spectral resolution below 3 nm is experimentally demonstrated.

Silicon microring resonators

Abstract: An overview is presented of the current state-of-the-art in silicon nanophotonic ring resonators. Basic theory of ring resonators is discussed, and applied to the peculiarities of submicron silicon photonic wire waveguides: the small dimensions and tight bend radii, sensitivity to perturbations and the boundary conditions of the fabrication processes. Theory is compared to quantitative measurements. Finally, several of the more promising applications of silicon ring resonators are discussed: filters and optical delay lines, label-free biosensors, and active rings for efficient modulators and even light sources.

Device Requirements for Optical Interconnects to Silicon Chips

Abstract: We examine the current performance and future demands of interconnects to and on silicon chips. We compare electrical and optical interconnects and project the requirements for optoelectronic and optical devices if optics is to solve the major problems of interconnects for future high-performance silicon chips. Optics has potential benefits in interconnect density, energy, and timing. The necessity of low interconnect energy imposes low limits especially on the energy of the optical output devices, with a ~ 10 fJ/bit device energy target emerging. Some optical modulators and radical laser approaches may meet this requirement. Low (e.g., a few femtofarads or less) photodetector capacitance is important. Very compact wavelength splitters are essential for connecting the information to fibers. Dense waveguides are necessary on-chip or on boards for guided wave optical approaches, especially if very high clock rates or dense wavelength-division multiplexing (WDM) is to be avoided. Free-space optics potentially can handle the necessary bandwidths even without fast clocks or WDM. With such technology, however, optics may enable the continued scaling of interconnect capacity required by future chips.

All-optical control of light on a silicon chip

Abstract: Photonic circuits, in which beams of light redirect the flow of other beams of light, are a long-standing goal for developing highly integrated optical communication components1,2,3. Furthermore, it is highly desirable to use silicon—the dominant material in the microelectronic industry—as the platform for such circuits. Photonic structures that bend, split, couple and filter light have recently been demonstrated in silicon4,5, but the flow of light in these structures is predetermined and cannot be readily modulated during operation. All-optical switches and modulators have been demonstrated with III–V compound semiconductors6,7, but achieving the same in silicon is challenging owing to its relatively weak nonlinear optical properties. Indeed, all-optical switching in silicon has only been achieved by using extremely high powers8,9,10,11,12,13,14,15 in large or non-planar structures, where the modulated light is propagating out-of-plane. Such high powers, large dimensions and non-planar geometries are inappropriate for effective on-chip integration. Here we present the experimental demonstration of fast all-optical switching on silicon using highly light-confining structures to enhance the sensitivity of light to small changes in refractive index. The transmission of the structure can be modulated by up to 94% in less than 500 ps using light pulses with energies as low as 25 pJ. These results confirm the recent theoretical prediction16 of efficient optical switching in silicon using resonant structures.

Guiding, modulating, and emitting light on Silicon-challenges and opportunities

Abstract: Silicon photonics could enable a chip-scale platform for monolithic integration of optics and microelectronics for applications of optical interconnects in which high data streams are required in a small footprint. This paper discusses mechanisms in silicon photonics for waveguiding, modulating, light amplification, and emission. These mechanisms, together with recent advances of fabrication techniques, have enabled the demonstration of ultracompact passive and active silicon photonic components with very low loss.

A surface-emitting laser incorporating a high-index-contrast subwavelength grating

Abstract: Semiconductor diode lasers can be used in a variety of applications including telecommunications, displays, solid-state lighting, sensing and printing. Among them, vertical-cavity surface-emitting lasers1,2,3 (VCSELs) are particularly promising. Because they emit light normal to the constituent wafer surface, it is possible to extract light more efficiently and to fabricate two-dimensional device arrays. A VCSEL contains two distributed Bragg reflector (DBR) mirrors for optical feedback, separated by a very short active gain region. Typically, the reflectivity of the DBRs must exceed 99.5% in order for the VCSEL to lase. However, the realization of practical VCSELs that can be used over a broad spectrum of wavelengths has been hindered by the poor optical and thermal properties of candidate DBR materials4,5,6. In this Letter, we present surface-emitting lasers that incorporate a single-layer high-index-contrast subwavelength grating7,8 (HCG). The HCG provides both efficient optical feedback and control of the wavelength and polarization of the emitted light. Such integration reduces the required VCSEL mirror epitaxial thickness by a factor of two and increases fabrication tolerance. This work will directly influence the future designs of VCSELs, photovoltaic cells and light-emitting diodes at blue–green, 1.3–1.55 µm and mid- to far-infrared wavelengths.