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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 1 . 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 2 , 3 , 4 , 5 , 6 and/or electro-optic materials such as lithium niobate 7 , 8 , 9 . To date, the fastest silicon-waveguide-based optical modulator that has been demonstrated experimentally has a modulation frequency of only ∼20 MHz (refs 10 , 11 ), although it has been predicted theoretically that a ∼1-GHz modulation frequency might be achievable in some device structures 12 , 13 . 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.

Accurate three-dimensional (3D) imaging is essential for machines to map and interact with the physical world 1 , 2 . Although numerous 3D imaging technologies exist, each addressing niche applications with varying degrees of success, none has achieved the breadth of applicability and impact that digital image sensors have in the two-dimensional imaging world 3 – 10 . A large-scale two-dimensional array of coherent detector pixels operating as a light detection and ranging system could serve as a universal 3D imaging platform. Such a system would offer high depth accuracy and immunity to interference from sunlight, as well as the ability to measure the velocity of moving objects directly 11 . Owing to difficulties in providing electrical and photonic connections to every pixel, previous systems have been restricted to fewer than 20 pixels 12 – 15 . Here we demonstrate the operation of a large-scale coherent detector array, consisting of 512 pixels, in a 3D imaging system. Leveraging recent advances in the monolithic integration of photonic and electronic circuits, a dense array of optical heterodyne detectors is combined with an integrated electronic readout architecture, enabling straightforward scaling to arbitrarily large arrays. Two-axis solid-state beam steering eliminates any trade-off between field of view and range. Operating at the quantum noise limit 16 , 17 , our system achieves an accuracy of 3.1 millimetres at a distance of 75 metres when using only 4 milliwatts of light, an order of magnitude more accurate than existing solid-state systems at such ranges. Future reductions of pixel size using state-of-the-art components could yield resolutions in excess of 20 megapixels for arrays the size of a consumer camera sensor. This result paves the way for the development and proliferation of low-cost, compact and high-performance 3D imaging cameras that could be used in applications from robotics and autonomous navigation to augmented reality and healthcare. A compact, high-performance silicon photonics-based light detection and ranging system for three-dimensional imaging is developed that should be amenable to low-cost mass manufacturing

Bright future for ‘optical’ silicon With the growing use of optoelectronics in information technology, manipulating light is almost as important as manipulating electrons. Unfortunately silicon, workhorse of modern microelectronics, is next to useless in optical applications. There has been a massive effort to overcome silicon's inadequacies, and ways of coaxing silicon to handle light are under development but a key component — the laser — has been problematic. Last year a silicon laser was produced, but it involved metres of optical fibre. Now workers in Intel's research labs have come up with an all-silicon laser on a single chip. The device is compact and readily integrated with other silicon components. The possibility of light generation and/or amplification in silicon has attracted a great deal of attention 1 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 2 , 3 , 4 , 5 , Si/SiO 2 superlattices 6 , erbium-doped silicon-rich oxides 7 , 8 , 9 , 10 , surface-textured bulk silicon 11 and Si/SiGe quantum cascade structures 12 . Stimulated Raman scattering (SRS) has recently been demonstrated as a mechanism to generate optical gain in planar silicon waveguide structures 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 . 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 18 , 19 , 20 , 21 . 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 22 . 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.

Accurate 3D imaging is essential for machines to map and interact with the physical world. While numerous 3D imaging technologies exist, each addressing niche applications with varying degrees of success, none have achieved the breadth of applicability and impact that digital image sensors have achieved in the 2D imaging world. A large-scale two-dimensional array of coherent detector pixels operating as a light detection and ranging (LiDAR) system could serve as a universal 3D imaging platform. Such a system would offer high depth accuracy and immunity to interference from sunlight, as well as the ability to directly measure the velocity of moving objects. However, due to difficulties in providing electrical and photonic connections to every pixel, previous systems have been restricted to fewer than 20 pixels. Here, we demonstrate the first large-scale coherent detector array consisting of 512 (\\(32 16\\)) pixels, and its operation in a 3D imaging system. Leveraging recent advances in the monolithic integration of photonic and electronic circuits, a dense array of optical heterodyne detectors is combined with an integrated electronic readout architecture, enabling straightforward scaling to arbitrarily large arrays. Meanwhile, two-axis solid-state beam steering eliminates any tradeoff between field of view and range. Operating at the quantum noise limit, our system achieves an accuracy of \\(3.1~mm\\) at a distance of 75 metres using only \\(4~mW\\) of light, an order of magnitude more accurate than existing solid-state systems at such ranges. Future reductions of pixel size using state-of-the-art components could yield resolutions in excess of 20 megapixels for arrays the size of a consumer camera sensor. This result paves the way for the development and proliferation of low cost, compact, and high performance 3D imaging cameras.

Narrow linewidth operation of several lasers and optical amplifiers is demonstrated. Investigation of linewidth broadening in long pulse alexandrite lasers and a solution to correct the effect is described. A narrow linewidth, tunable, continuous wave device operating in the green spectral range was built using double clad single mode fiber technology, it provides 1.74 W at the fundamental wavelength, and 110 mW at the second harmonic wavelength. Its suitability for spectroscopy applications is proven by performing absorption spectroscopy on 127I2 and 129 I2. Finally, a new method to generate narrow linewidth high energy pulses in a very rugged setup is demonstrated. A multistage fiber amplifier that amplifies pulses to peak powers in excess of 100 W was built. These were then amplified to more than 1 MW peak power in a flashlamp pumped Nd:YAG rod.