| In this paper, we present a brief history of silicon photonics from the early research papers in the late 1980s and early 1990s, to the potentially revolutionary technology that exists today. Given that other papers in this special issue give detailed reviews of key aspects of the technology, this paper will concentrate on the key technological milestones that were crucial in demonstrating the capability of silicon photonics as both a successful technical platform, as well as indicating the potential for commercial success. The paper encompasses discussion of the key technology areas of passive devices, modulators, detectors, light sources, and system integration.In so doing, the paper will also serve as an introduction to the other papers within this special issue.

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Abstract:The design and characterization of silicon-on-insulator midinfrared spectrometers operating at 3.8μm is reported. The devices are fabricated on 200mm SOI wafers in a CMOS pilot line. Both arrayed waveguide grating structures and planar concave grating structures were designed and tested. Low insertion loss (1.5-2.5dB) and good crosstalk characteristics (15-20dB) are demonstrated, together with waveguide propagation losses in the range of 3 to 6dB/cm.

We present a simple and practical strategy that allows to design high-efficiency grating couplers. The technique is based on the simultaneous apodization of two structural parameters: the grating period and the fill-factor, along with the optimization of the grating coupler etching depth. Considering a 260 nm Si-thick Silicon-on-insulator platform, we numerically demonstrated a coupling efficiency of −0.8 dB (83%), well matching the experimental value of −0.9 dB (81%). Thanks to the optimized design, these results represent the best performance ever reported in the literature for SOI structures without the use of any back-reflector.

Due to its excellent electronic and photonic properties, silicon is a good candidate for mid-infrared optoelectronic devices and systems that can be used in a host of applications. In this paper we review some of the results reported recently, and we also present several new results on midinfrared photonic devices including Mach-Zehnder interferometers, multimode interference splitters and multiplexers based on silicon-oninsulator, polysilicon, suspended silicon, and slot waveguide platforms.

We propose the use of subwavelength structures in a waveguide grating to achieve polarization-independent coupling of light between an optical fiber and a silicon-on-insulator (SOI) optical waveguide. The subwavelength structure allows the mode effective indices of the TE and TM modes in the grating section to be precisely engineered. We calculate that coupling efficiency of over 64% is possible using the proposed design for polarization-independent coupling between single-mode optical fibers and SOI nanophotonic waveguides.

We propose and experimentally demonstrate a novel subwavelength grating coupler on silicon-on-insulator, for coupling to optical fibers with a wide optical bandwidth. Theoretical analysis and design optimization of the coupler are described. About 73 nm 1 dB bandwidth was experimentally demonstrated with -5.6  dB coupling efficiency. Better than -3.4  dB efficiency with 86 nm 1 dB bandwidth is predicted for these structures with optimized buried oxide thickness.

A fter an impressive initial spurt of progress in device engineering during the early 2000s when the optical communications industry saw unprecedented levels of investment, silicon photonics continues to develop at an amazing pace. Many novel applications and devices are emerging. Silicon photonics has the potential to become a major platform for optoelectronic integrated circuits (OEICs) and to be used in high-speed optical interconnects for chip-level data communications because of the extremely large bandwidth and high speed off ered by optical communications. Many challenges have been addressed through the introduction of innovative ideas, paving the way for the practical deployment of silicon-based optoelectronic devices and integrated photonic circuits in computing and telecommunication systems [1]. Th e commercialization of silicon photonics, originally driven by applications in telecommunications, is now also driven by the needs of the computing industry for highspeed, energy-effi cient optical cable technology, such as the Light Peak Technology under development by Intel (USA). Th e California-based company Luxtera (USA) has also commercialized a series of siliconphotonic transceiver systems.Silicon off ers many advantages over alternative material systems (e.g. InP, GaAs, LiNbO 3 ) for OEIC applications. One major reason for the wide interest that silicon photonics is attracting is the cost advantage that silicon photonics can potentially off er through its compatibility with the complementary metal-oxide-semiconductor (CMOS) fabrication processes used in the microelectronics industry. Th e huge investments that have been made in CMOS microelectronics fabrication technologies has resulted in processes that off er much higher yield than is possible using alternative materials for photonics, thus making feasible large-scale integration and the production of silicon-photonic devices that are monolithically integrated with not only optical components but also electronic circuits in the same platform at ultrahigh density. Another reason for the attractiveness of silicon photonics is the high refractive index contrast between the silicon core (refractive index, 3.48) and silicon dioxide cladding (refractive index, 1.45) in silicon-on-insulator (SOI) devices, which ensures the submicrometer confi nement of light and allows tight bending in optical waveguides. Th e high-density integration of photonic circuits on SOI platforms is thus feasible. Th e low cost of high-quality SOI wafers is another advantage of silicon photonics. All kinds of low-cost devices enabled by silicon photonics are therefore predicted, and these may also enjoy the other benefi ts of monolithic integration: smaller size, increased power effi ciency and improved reliability. Figure 1 shows an example of a high-density integrated photonics devices fabricated on a 6-inch SOI wafer using CMOS-compatible technology.In this article, we review some of the exciting progress that has been made in silicon photonics with the aim of providing a broa...