Silicon has long been the optimal material for electronics, but it is only relatively recently that it has been considered as a material option for photonics. One of the key limitations for using silicon as a photonic material has been the relatively low speed of silicon optical modulators compared to those fabricated from III-V semiconductor compounds and/or electro-optic materials such as lithium niobate. To date, the fastest silicon-waveguide-based optical modulator that has been demonstrated experimentally has a modulation frequency of only approximately 20 MHz (refs 10, 11), although it has been predicted theoretically that a approximately 1-GHz modulation frequency might be achievable in some device structures. Here we describe an approach based on a metal-oxide-semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation: we demonstrate an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz. As this technology is compatible with conventional complementary MOS (CMOS) processing, monolithic integration of the silicon modulator with advanced electronics on a single silicon substrate becomes possible.

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The possibility of light generation and/or amplification in silicon has attracted a great deal of attention for silicon-based optoelectronic applications owing to the potential for forming inexpensive, monolithic integrated optical components. Because of its indirect bandgap, bulk silicon shows very inefficient band-to-band radiative electron-hole recombination. Light emission in silicon has thus focused on the use of silicon engineered materials such as nanocrystals, Si/SiO2 superlattices, erbium-doped silicon-rich oxides, surface-textured bulk silicon and Si/SiGe quantum cascade structures. Stimulated Raman scattering (SRS) has recently been demonstrated as a mechanism to generate optical gain in planar silicon waveguide structures. In fact, net optical gain in the range 2-11 dB due to SRS has been reported in centimetre-sized silicon waveguides using pulsed pumping. Recently, a lasing experiment involving silicon as the gain medium by way of SRS was reported, where the ring laser cavity was formed by an 8-m-long optical fibre. Here we report the experimental demonstration of Raman lasing in a compact, all-silicon, waveguide cavity on a single silicon chip. This demonstration represents an important step towards producing practical continuous-wave optical amplifiers and lasers that could be integrated with other optoelectronic components onto CMOS-compatible silicon chips.

We present a high-speed and highly scalable silicon optical modulator based on the free carrier plasma dispersion effect. The fast refractive index modulation of the device is due to electric-field-induced carrier depletion in a Silicon-on-Insulator waveguide containing a reverse biased pn junction. To achieve high-speed performance, a travelling-wave design is used to allow co-propagation of electrical and optical signals along the waveguide. We demonstrate high-frequency modulator optical response with 3 dB bandwidth of ~20 GHz and data transmission up to 30 Gb/s. Such high-speed data transmission capability will enable silicon modulators to be one of the key building blocks for integrated silicon photonic chips for next generation communication networks as well as future high performance computing applications.

We demonstrate a silicon modulator with an intrinsic bandwidth of 10 GHz and data transmission from 6 Gbps to 10 Gbps. Such unprecedented bandwidth performance in silicon is achieved through improvements in material quality, device design, and driver circuitry.

We observe for the first time net optical gain in a low loss silicon waveguide in silicon-on-insulator (SOI) based on stimulated Raman scattering with a pulsed pump laser at 1.545 microm. We show that pulsed pumping with a pulse width narrower than the carrier recombination lifetime in SOI significantly reduces the free carrier generation rate due to two-photon absorption (TPA) in silicon. For a 4.8 cm long waveguide with an effective core area of ~1.57 microm2, we obtained a net gain of 2 dB with a pump pulse width of ~17 ns and a peak pump power of ~470 mW inside the waveguide.

We observe for the first time net continuous wave optical gain in a low loss silicon-on-insulator waveguide based on stimulated Raman scattering. We show that nonlinear optical loss due to two-photon absorption induced free carrier absorption can be significantly reduced by introducing a reverse biased p-i-n diode in the waveguide. For a 4.8 cm long waveguide with an effective core area of ~1.6 microm2, we obtain a net CW Raman gain of > 3dB with a pump power of ~700mW inside the waveguide.

Efficient wavelength conversion via four-wave-mixing in silicon-on-isolator p-i-n waveguides has been realized. By reverse biasing the p-i-n diode structure formed along the silicon rib waveguide, the nonlinear absorption due to two photon absorption induced free carrier absorption is significantly reduced, and a wavelength conversion efficiency of -8.5 dB has been achieved in an 8 cm long waveguide at a pump intensity of 40 MW/cm2. A high-speed pseudo-random bit sequence data at 10 Gb/s rate is converted to a new wavelength channel in the C-band with clear open eye diagram and no waveform distortion. Conversion efficiency as functions of pump power, wavelength detuning, and bias voltages, have been investigated. For shorter waveguides of 1.6 cm long, a conversion bandwidth of > 30 nm was achieved.