Marie-Josée Picard

Eliminating the birefringence in silicon-on-insulator ridge waveguides by use of cladding stress

We propose and demonstrate the use of the cladding stress-induced photoelastic effect to eliminate modal birefringence in silicon-on-insulator (SOI) ridge waveguides. Birefringence-free operation was achieved for waveguides with otherwise large birefringence by use of properly chosen thickness and stress of the upper cladding layer. With the stress levels typically found in cladding materials such as SiO2, the birefringence modification range can be as large as 10(-3). In arrayed waveguide grating demultiplexers that were fabricated in a SOI platform, we demonstrated the reduction of the birefringence from 1.2 x 10(-3) (without the upper cladding) to 4.5 x 10(-5) when a 0.8-microm oxide upper cladding with a stress of -320 MPa (compressive) was used. Because the index changes induced by the stress are orders of magnitude smaller than the waveguide core-cladding index contrast, the associated mode mismatch loss is negligible.

Microphotonic Elements for Integration on the Silicon-on-Insulator Waveguide Platform

This paper presents an overview of our recent work on several fundamental optical elements and their integration on the silicon-on-insulator (SOI) waveguide platform. Theory, design and experimental results are presented for monolithically integrated asymmetric graded-index waveguide couplers, as well as output couplers based on total internal reflection mirrors. Design strategies for dispersive elements on SOI, for example, ring resonators and arrayed waveguide gratings, are discussed with special emphasis on methods to eliminate the polarization sensitivity. Finally, the properties and applications of evanescent fields in SOI waveguides are reviewed

Broadband polarization independent nanophotonic coupler for silicon waveguides with ultra-high efficiency.

Coupling of light to and from integrated optical circuits has been recognized as a major practical challenge since the early years of photonics. The coupling is particularly difficult for high index contrast waveguides such as silicon-on-insulator, since the cross-sectional area of silicon wire waveguides is more than two orders of magnitude smaller than that of a standard single-mode fiber. Here, we experimentally demonstrate unprecedented control over the light coupling between the optical fiber and silicon chip by constructing the nanophotonic coupler with ultra-high coupling efficiency simultaneously for both transverse electric and transverse magnetic polarizations. We specifically demonstrate a subwavelength refractive index engineered nanostructure to mitigate loss and wavelength resonances by suppressing diffraction effects, enabling a coupling efficiency over 92% (0.32 dB) and polarization independent operation for a broad spectral range exceeding 100 nm.

A 100-channel near-infrared SOI waveguide microspectrometer: design and fabrication challenges

We present recent advances in the development of a waveguide microspectrometer chip with high spectral resolution in the near-infrared part of the spectrum. The microspectrometer is designed for a high index contrast silicon-on-insulator (SOI) platform, where high number of spectral channels can be obtained with high spectral resolution in a compact device. We present a 100-channel SOI microspectrometer with designed spectral resolution of ~0.08 nm at 1.5 μm wavelength and about 8x8 mm2 in size. A number of critical design issues are discussed, including design of deep-etched tapers near the Rowland circle required for high-resolution performance as well as coupling between closely spaced waveguides. Device fabrication process is discussed in detail, including two-step e-beam patterning and two-level ICP etches, the focus being on achieving deep and smooth vertical etches in silicon with controllable sub-micron waveguide widths and gaps. The potentially available spectral range of the microspectrometer is limited by the transparency of silicon, extending from the band edge of Si at 1.107 μm to the onset of lattice phonon absorption band near 5 μm. Such compact high-resolution multi-channel integrated microspectrometers are promising for a variety of applications, including spectroscopy, telecommunications, optical interconnects, environmental and bio-sensing.

Laser synthesizer of the ALMA telescope: Design and performance

The Laser Synthesizer of the Atacama Large Millimiter Array telescope in Chile has been designed and built by TeraXion. We present the design and performance achieved with this instrument.

Control and compensation of birefringence in SOI waveguides

In this paper, the theoretical and experimental studies of SOI waveguide birefringence as controlled by cladding stress properties were reported. The experimental birefringence was obtained from array waveguide grating (AWG) demultiplexer /spl Delta//spl lambda/ measurements. A finite element simulator (FEMLAB), to analyse the stress and the corresponding birefringence in SOI ridge waveguides, was used.

Generalized full-vector multi-mode matching analysis of whispering gallery microcavities

We outline a full-vectorial three-dimensional multi-mode matching technique in a cylindrical coordinate system that addresses the mutual coupling among multiple modes co-propagating in a perturbed whispering gallery mode microcavity. In addition to its superior accuracy in respect to our previously implemented single-mode matching technique, this current technique is suitable for modelling waveguide-to-cavity coupling where the influence of multi-mode coupling is non-negligible. Using this methodology, a robust scheme for hybrid integration of a microcavity onto a silicon-on-insulator platform is proposed.

Ring resonator in a Sagnac loop

A study of a ring resonator in a Sagnac loop is presented. The results of a theoretical analysis based on Jones calculus are confirmed by experiments. Comparison of a ring resonator in a Sagnac loop with a ring only is performed, and the advantages of our scheme are pointed out. The scheme can be used to increase the measurement sensitivity to small birefringence and associated polarization mode dispersion and to decrease the threshold for Sagnac-loop-based nonlinear switching and laser mode locking.

Bragg grating notch filters in silicon-on-insulator waveguides

Bragg gratings containing a central π phase shift or used in a Fabry-Perot configuration are found to provide ultra-narrow spectral features. Transmission notches having a full width at half maximum as small as 530 MHz (4.3 pm) are reported.

Stress-induced birefringence in silicon-on-insulator (SOI) waveguides

We show that stress engineering can be used to adjust the SOI waveguide birefringence to the stringent polarization tolerances expected of commercial devices, using only standard silicon processes. With decreasing device dimensions and high index contrast the waveguide birefringence becomes increasingly sensitive to device geometry. As a result, it is almost impossible to eliminate waveguide birefringence by adjusting waveguide profile alone. This paper presents, for the first time, a systematic study of the stress-induced birefringence of SOI waveguides. Through full-vectorial finite-element simulations, we investigate the variation of stress-induced birefringence with waveguide core and cladding geometries. It is found that the stress-induced birefringence is determined by the waveguide cross-section, the upper cladding layer thickness, and film stress levels. We develop a waveguide model that predicts the total waveguide birefringence and guides the post-fabrication processing steps. An experimental demonstration of a polarization insensitive SOI arrayed waveguide grating (AWG) demultiplexer is presented. The polarization dependent wavelength shifts measured experimentally agree well with the simulations.