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In the last few years, strained silicon has been proposed as a potential electro-optic material, paving the way to the realization of ultrafast modulators which are compatible with the CMOS fabrication technology. The linear Pockels effect has been used for measuring the magnitude of the induced \chi ^(2) components, with values reaching hundreds of \textpm/V. Recently, it has been shown that these values could have been overestimated due to the contribution of free carriers to the electro-optic modulation. In this work, this hypothesis is validated by a series of experimental observations, which are performed on strained silicon racetrack resonators. These are fabricated with different waveguide widths and orientations. We use a low frequency (KHz) homodyne detection technique to monitor the electro-optic response of the devices. The results indicate that the modulation strength is not dependent on the waveguide geometry or direction. A lot of anomalies are encountered in the device response, which are not compatible with a modulation mechanism of \chi ^(2) origin. To this purporse, a theory based on the nonlinear injection of free carriers inside the waveguide is presented. This is able to account for all the observed anomalies. [ABSTRACT FROM PUBLISHER]

Coupling of light to and from a microdisk resonator is a crucial step for the integration of this photonic structure in a photonic integrated circuit. However, the most common lateral coupling scheme, based on a point contact with a coplanar bus waveguide, suffers from strong wavelength dependence. This is a limiting factor for exciting efficiently the resonant modes in a broad spectral region. In the present paper, we propose a solution based on a different configuration, known as vertical coupling configuration, where a bus waveguide is buried below the micro disk. We demonstrate theoretically and experimentally that the long interaction region provided by this geometry allows to extend the optimal coupling spectral range from IR to visible. This feature constitutes a remarkable advantage over the usual laterally coupled devices for many different applications, such as frequency conversion, allowing bandwidth limitations to be significantly diminished. [ABSTRACT FROM PUBLISHER]

In this paper, we report on the design, fabrication, and characterization of a photonic circuit for biosensing applications. Silicon oxynitride with a bulk refractive index of 1.66 is the core-layer material. The photonic circuit is optimized for a wavelength of ∼850 nm, which allows on-chip integration of the light source via cost effective vertical-cavity surface-emitting lasers and of the detector by using standard silicon photodetectors. Design as well as fabrication processes are explained in details. The best characteristics for the single optical components in the photonic circuit are: for single-mode channel waveguides with dimensions of 350 nm × 950 nm; propagation losses of 0.8 dB/cm; bending losses of 0.1 dB/90°-bend (radius of curvature 100 μm); 49/51 splitting ratio for 3-dB power splitters (directional couplers); quality factors up to 1.3 × 105 for microring resonators. Volumetric sensing yields a bulk sensitivity of 80 nm/RIU and a limit of detection of 3 × 10−6 RIU. Therefore, SiON-based photonic circuits represent a reliable material platform for biosensing in the short-wave near infrared region. [ABSTRACT FROM PUBLISHER]

We report on the realization of a silicon-based microresonator/waveguide coupled system, fully integrated on a silicon chip. The device uses a vertical coupling scheme of the resonator and a buried strip waveguide. We demonstrate that its high optical quality follows from the accurate planarization of the waveguide topography, which is achieved by multiple depositions-and-reflows of a borophosphosilicate glass over strip waveguides. More importantly, we demonstrate wafer-scale mass fabrication of freestanding planar resonators suspended in air and coupled to integrated bus waveguides, as well as controlled selective excitation of different mode families of the resonator. This opens the door for the realization of stable all-integrated complex resonator systems for optomechanical and metrological applications, with the potential to substitute today's intensive use of complicated fiber-taper coupling schemes. [ABSTRACT FROM PUBLISHER]

Lists the reviewers who contributed to IEEE Photonics Technology Letters in 2011. [ABSTRACT FROM PUBLISHER]