Pavel Cheben

Richard Soref

David Lockwood

Graham Reed

Silicon Photonics

Transistor scaling alone can no longer be relied upon to yield the exponential speed increases we have come to expect from the microprocessor industry. The principle reason for this is the <i>interconnect bottleneck</i>, where the electrical connections between and within microprocessors are becoming, and in some cases have already become, the limiting factor in overall microprocessor performance. Optical interconnects have the potential to address this shortcoming directly, by providing an inter- and intrachip communication infrastructure that has both greater bandwidth and lower latency than electrical interconnects, while remaining safely within size and power constraints. In this paper, we review the requirements that a successful optical interconnect must meet, as well as some of the recent work in our group in the area of slow-light photonic crystal devices for on-chip optical interconnects. We show that slow-light interferometric optical modulators in photonic crystal can have not only high bandwidth, but also extremely compact size. We also introduce the first example of a multichannel slow light platform, upon which a new class of ultracompact optical devices can be built.

Sean P. Anderson

Ashutosh R. Shroff

Philippe M. Fauchet

Slow Light with Photonic Crystals for On-Chip Optical Interconnects

First implementations of subwavelength gratings (SWGs) in silicon-on-insulator (SOI) waveguides are discussed and demonstrated by experiment and simulations. The subwavelength effect is exploited for making antireflective and highly reflective waveguide facets as well as efficient fiber-chip coupling structures. We demonstrate experimentally that by etching triangular SWGs into SOI waveguide facets, the facet power reflectivity can be reduced from 31&#x25; to &#x3C;2.5&#x25;. Similar structures using square gratings can also be used to achieve high facet reflectivity. Finite 
difference time-domain simulations show that &#x3E;94&#x25; facet reflectivity can be achieved with square SWGs for 5&#x2009;<svg style="vertical-align:-2.29482pt;width:9.6374998px;" id="M1" height="9.6750002" version="1.1" viewBox="0 0 9.6374998 9.6750002" width="9.6374998"  xmlns="http://www.w3.org/2000/svg">
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</svg>m thick SOI waveguides. Finally, SWG fiber-chip couplers for SOI photonic wire waveguides are introduced, including design, 
simulation, and first experimental results.

J. H. Schmid

P. Cheben

S. Janz

J. Lapointe

E. Post

A. Del&#226;ge

A. Densmore

B. Lamontagne

P. Waldron

D.-X. Xu

Subwavelength Grating Structures in Silicon-on-Insulator Waveguides

Integrated photonics via Si CMOS technology has been a strategic area since electronics and photonics convergence should be the next platform for information technology. The platform is recently referred to as “Si photonics” that attracts much interest of researchers in industries as well as academia in the world. The main goal of Si Photonics is currently to reduce material diversity of photonic devices to pursuing CMOS-compatibility. In contrast, the present paper proposes another route of Si Photonics, reducing diversity of photonic devices. The proposed device unifying functionality of photonics is a microresonator with a pin diode structure that enables the Purcell effect and Franz-Keldysh effect to emit and to modulate light from SiGe alloys.

Kazumi Wada

A New Approach of Electronics and Photonics Convergence on Si CMOS Platform: How to Reduce Device Diversity of Photonics for Integration

A brief overview of silicon photonics is given here in order to provide a context for invited and contributed papers in this special issue. Recent progress on silicon-based photonic components, photonic integrated circuits, and optoelectronic integrated circuits is surveyed.  Present and potential applications are identified along with the scientific and engineering challenges that must be met in order to actualize applications. Some on-going government-sponsored projects in silicon optoelectronics are also described.

The Achievements and Challenges of Silicon Photonics

Silicon the material per excellence for electronics is not used for sourcing light due to the lack of efficient light emitters and lasers. In this review, after having introduced the basics on lasing, I will discuss the physical reasons why silicon is not a laser material and the approaches to make it lasing. I will start with bulk silicon, then I will discuss silicon nanocrystals and <svg style="vertical-align:-0.0pt;width:28.4625px;" id="M1" height="13.775" version="1.1" viewBox="0 0 28.4625 13.775" width="28.4625" xmlns="http://www.w3.org/2000/svg"><g transform="matrix(1.25,0,0,-1.25,0,13.775)"><g transform="translate(72,-60.98)"><text transform="matrix(1,0,0,-1,-71.95,61.03)"><tspan style="font-size: 12.50px; " x="0" y="0">E</tspan><tspan style="font-size: 12.50px; " x="7.6393328" y="0">r</tspan></text><text transform="matrix(1,0,0,-1,-60.15,66.03)"><tspan style="font-size: 8.75px; " x="0" y="0">3</tspan><tspan style="font-size: 8.75px; " x="4.3759999" y="0">+</tspan></text></g></g></svg> coupled silicon nanocrystals where significant advances have been done in the past and can be expected in the near future. I will conclude with an optimistic note on silicon lasing.

L. Pavesi

Silicon-Based Light Sources for Silicon Integrated Circuits

Silicon nanocrystals (NCs) represent one of the most promising material systems for light emission applications in microphotonics. In recent years, several groups have reported on the observation of optical gain or stimulated emission in silicon NCs or in porous silicon (PSi). These results suggest that silicon-NC-based waveguide amplifiers or silicon lasers are achievable. However, in order to obtain clear and reproducible evidence of stimulated emission, it is necessary to understand the physical mechanisms at work in the light emission process. In this paper, we report on the detailed theoretical aspects of the energy levels and recombination rates in doped and undoped Si NCs, and we discuss the effects of energy transfer mechanisms. The theoretical calculations are extended toward computational simulations of ensembles of interacting nanocrystals. We will show that inhomogeneous broadening and energy transfer remain significant problems that must be overcome in order to improve the gain profile and to minimize nonradiative effects. Finally, we suggest means by which these objectives may be achieved.

V. A. Belyakov

V. A. Burdov

R. Lockwood

A. Meldrum

Silicon Nanocrystals: Fundamental Theory and Implications for Stimulated Emission

We review the use of the oxide cladding stress-induced photoelastic effect to modify the polarization dependent properties in silicon-on-insulator (SOI) waveguide components, and highlight characteristics particular to this high index contrast (HIC) systems. The birefringence in SOI waveguides has its origin in the electromagnetic boundary conditions at the waveguide boundaries, and can be further modified by the presence of stress in the waveguiding materials. With typical stress levels in <svg style="vertical-align:-3.13504pt;width:30.5375px;" id="M1" height="14.7125" version="1.1" viewBox="0 0 30.5375 14.7125" width="30.5375"  xmlns="http://www.w3.org/2000/svg">
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</svg> films, which are often used as the upper cladding, the waveguide effective index can be altered anisotropically up to the order of <svg style="vertical-align:-0.17555pt;width:29.3375px;" id="M2" height="14.2" version="1.1" viewBox="0 0 29.3375 14.2" width="29.3375"  xmlns="http://www.w3.org/2000/svg">
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</svg>m. This effect can be used effectively to counter the waveguide geometrical birefringence, allowing the waveguide cross-section profiles to be optimized for design criteria other than null geometrical birefringence. Design strategies are developed for using stress engineering to achieve a variety of functions. Polarization insensitive arrayed waveguide gratings (AWGs), polarization insensitive ring resonators, and polarization splitters and filters are demonstrated using these design principles.

W. N. Ye

Stress Induced Effects for Advanced Polarization Control in Silicon Photonics Components

It is well known that robust and reliable photonic crystal structures can be  manufactured with very high precision by electrochemical etching of silicon wafers, which results in two- and three-dimensional photonic crystals made of macroporous silicon. However, tuning of the photonic properties is necessary in order to apply these promising structures in integrated optical devices. For this purpose, different effects have been studied, such as the infiltration with addressable dielectric liquids (liquid crystals), the utilization of Kerr-like nonlinearities of the silicon, or free-charge carrier injection by means of linear (one-photon) and nonlinear (two-photon) absorptions. The present article  provides a review, critical discussion, and perspectives about state-of-the-art tuning capabilities.

Heinz-S. Kitzerow

Heinrich Matthias

Stefan L. Schweizer

Henry M. van Driel

Ralf B. Wehrspohn

Tuning of the Optical Properties in Photonic Crystals Made of Macroporous Silicon

We review our recent studies on all-optical switching and memory operations based on thermo-optic and carrier-plasma nonlinearities both induced by two-photon absorption in silicon photonic crystal nanocavities. Owing to high-<i>Q</i> and small volume of these photonic crystal cavities, we have demonstrated that the switching power can be largely reduced. In addition, we demonstrate that the switching time is also reduced in nanocavity devices because of their short diffusion time. These features are important for all-optical nonlinear processing in silicon photonics technologies, since silicon is not an efficient optical nonlinear material. We discuss the effect of the carrier diffusion process in our devices, and demonstrate improvement in terms of the response speed by employing ion-implantation process. Finally, we show that coupled bistable devices lead to all-optical logic, such as flip-flop operation. These results indicate that a nanocavity-based photonic crystal platform on a silicon chip may be a promising candidate for future on-chip all-optical information processing in a largely integrated fashion.

Masaya Notomi

Takasumi Tanabe

Akihiko Shinya

Eiichi Kuramochi

Hideaki Taniyama

On-Chip All-Optical Switching and Memory by Silicon Photonic Crystal Nanocavities

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