Mehdi Asghari

Tapered silicon waveguides for low insertion loss highly-efficient high-speed electronic variable optical attenuators

In this paper we describe our recently developed NVT mode-matching epitaxial adiabatic tapered waveguide technology, and show that it leads to a dramatic reduction of insertion loss in an integrated silicon waveguide. We have introduced the NVT process into a four-channel silicon-on-insulator (SOI) EVOA which relies on current injection to alter the level of free-carrier absorption in the silicon waveguide and thus allows the precise electronic control of optical attenuation.

Silicon-on-Insulator-Based Planar Circuit for Passive Optical Network Applications

A novel design of a silicon-on-insulator (SOI) filter for passive optical network applications is described. The SOI filter comprises a monolithically integrated planar reflective grating and a multistage Mach-Zehnder interferometer. The fabricated device showed low insertion losses and high optical isolation. To the best of our knowledge, this letter describes the first demonstration of an SOI circuit comprising monolithically integrated planar reflective grating and cascaded Mach-Zehnder interferometer

Fabrication Insensitive Echelle Grating in Silicon-on-Insulator Platform

We demonstrate a compact, low crosstalk, low loss, and flat passband demultiplexer based on an echelle grating fabricated in the silicon-on-insulator (SOI) platform. The demonstrated 12 channel demultiplexer has an 8-nm channel spacing, 5.5-nm flat passband, 1.7-dB on-chip loss, and better than 25-dB optical crosstalk. By arranging the output waveguides very close to the zero degree angle of the echelle grating, the performance of the demonstrated device is made insensitive to the vertical angle of the grating facet. The fabricated devices have a very small footprint and have the potential to provide a low-cost demultiplexer solution for multichannel data transmission applications.

Low-Loss Polarization-Insensitive Silicon-on-Insulator-Based WDM Filter for Triplexer Applications

We have designed and fabricated a low-loss polarization-insensitive silicon-on-insulator-based photonic integrated circuit wavelength-division-multiplexing transceiver filter for triplexer applications. The filter is realized by two-stage Fourier-transform-based Mach-Zehnder interferometers to handle the uploading of 1.3-mum data stream and the demultiplexing of 1.49-mum/1.55-mum channels for downstream traffics, respectively. The fabricated filter has less than 0.2-dB ripple over 20-nm flat passband for downstream channels and more than 100-nm bandwidth for the upstream channel. The excess loss of the filter is less than 0.35 dB with less than 0.1-dB polarization-dependent loss.

Single-chip variable optical attenuator and multiplexer subsystem integration

We have presented a fully integrated 40 channel VOA-multiplexer subsystem, which delivers high performance with reduced fabrication and assembly complexity. This device demonstrates the potential of the SOI platform to enable low-cost subsystem integration for communication networks.

Silicon Photonics: A Low Cost Integration Platform for Datacom and Telecom Applications

Si photonics technology as a platform for the realization of cost effective products for telecom and datacom applications is reviewed and recent progress in the area is reported.

Silicon waveguide integrated optical switching with microsecond switching speed

Options for the design of a Mach-Zehnder switch based upon silicon waveguide technology are discussed. Results for a 2/spl times/2 thermo-optic device are presented showing a switching speed of /spl sim/10 /spl mu/s and an extinction ratio of 23.5 dB.

Recent progress in the design, simulation, and fabrication of small cross-section silicon-on-insulator VOAs

The principles of operation and general design criteria for PIN diode variable optical attenuators (VOAs) realized from silicon-on-insulator rib waveguide structures are described. We present as a benchmark the performance of devices based on the established VOA produced by Bookham Technology Plc, and demonstrate 25dB attenuation at less than 70mW with novel recessed dopant geometries. Optical and electrical simulation results for new, smaller cross-section VOA structures based on rib waveguides utilizing a 2mm high guiding layer are detailed and discussed. Experimental results demonstrating the successful fabrication of these structures and the significant improvements in performance attained are presented. In particular we show that the attenuation efficiency can be 30% higher than that of the larger structure, and that modulation bandwidths may approach 10MHz.

Novel fabrication tolerant flat-top demultiplexers based on etched diffraction gratings in SOI

Flat-top demultiplexers using etched diffraction gratings in the silicon-on-insulator (SOI) platform are reported and experimentally demonstrated. The novel design enables the loss and crosstalk of the devices to be insensitive to the vertical angle of the grating facets.

Progress in manufactured silicon photonics

While investment in sub-wavelength silicon photonics research has gained popularity, Kotura has forged significant customer traction with first generation silicon-photonics products by focusing on manufacturable designs and processes. This paper reviews recent gains in engineering developments where mature monolithic and hybrid methods are integrated to form high-performance manufacturable products with proven long-term reliability. Components and methods are described that lead to photonic modules and subsystems suitable for automated manufacturing techniques.