Wavelength-tunable silicon microring modulator.
TL;DR: This device aims to solve the narrow bandwidth problem of silicon microcavity modulators and increase the data bandwidth in optical interconnect systems.
Abstract: We present a wavelength-tunable, compact, high speed and low power silicon microring modulator. With a ring radius of 5 microm, we demonstrate a modulator with a high speed of 12.5 Gbps and a driving voltage of 3 V to achieve approximately 6 dB extinction ratio in high speed measurement. More importantly, tunability of the resonant wavelength is accomplished by means of a microheater on top of the ring, with an efficiency of 2.4 mW/nm (2.4 mW is needed to tune the resonant wavelength by 1 nm). This device aims to solve the narrow bandwidth problem of silicon microcavity modulators and increase the data bandwidth in optical interconnect systems.
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TL;DR: Up-to-date 2D material-based optical modulation in three categories is reviewed: free-space, fiber-based, and on-chip configurations and the outlook for future opportunities of these 2D materials for optical modulation is given.
Abstract: Owing to their atomic layer thickness, strong light–material interaction, high nonlinearity, broadband optical response, fast relaxation, controllable optoelectronic properties, and high compatibility with other photonic structures, 2D materials, including graphene, transition metal dichalcogenides and black phosphorus, have been attracting increasing attention for photonic applications. By tuning the carrier density via electrical or optical means that modifies their physical properties (e.g., Fermi level or nonlinear absorption), optical response of the 2D materials can be instantly changed, making them versatile nanostructures for optical modulation. Here, up-to-date 2D material-based optical modulation in three categories is reviewed: free-space, fiber-based, and on-chip configurations. By analysing cons and pros of different modulation approaches from material and mechanism aspects, the challenges faced by using these materials for device applications are presented. In addition, thermal effects (e.g., laser induced damage) in 2D materials, which are critical to practical applications, are also discussed. Finally, the outlook for future opportunities of these 2D materials for optical modulation is given.
361 citations
TL;DR: The use of free-standing silicon racetrack resonators with undercut structures significantly enhances the tuning efficiency, with one order of magnitude improvement of that for previously demonstrated thermo-optic devices without undercuts.
Abstract: We present thermally tunable silicon racetrack resonators with an ultralow tuning power of 2.4 mW per free spectral range. The use of free-standing silicon racetrack resonators with undercut structures significantly enhances the tuning efficiency, with one order of magnitude improvement of that for previously demonstrated thermo-optic devices without undercuts. The 10%-90% switching time is demonstrated to be ~170 µs. Such low-power tunable micro-resonators are particularly useful as multiplexing devices and wavelength-tunable silicon microcavity modulators.
341 citations
TL;DR: A high-speed ring modulator that fits many of the ideal qualities for optical interconnect in future exascale supercomputers and fits in a compact 400 μm2 footprint is reported.
Abstract: We report a high-speed ring modulator that fits many of the ideal qualities for optical interconnect in future exascale supercomputers. The device was fabricated in a 130nm SOI CMOS process, with 7.5μm ring radius. Its high-speed section, employing PN junction that works at carrier-depletion mode, enables 25Gb/s modulation and an extinction ratio >5dB with only 1V peak-to-peak driving. Its thermal tuning section allows the device to work in broad wavelength range, with a tuning efficiency of 0.19nm/mW. Based on microwave characterization and circuit modeling, the modulation energy is estimated ~7fJ/bit. The whole device fits in a compact 400μm2 footprint.
232 citations
TL;DR: A reconfigurable optical directed logic architecture that offers several significant improvements over the original directed logic presented by Hardy and Shamir is presented.
Abstract: We present a reconfigurable optical directed logic architecture that offers several significant improvements over the original directed logic presented by Hardy and Shamir. Specific embodiments of on-chip, waveguided, large-scale-integrated, cellular optical directed logic fabrics are proposed and analyzed. Five important logic functions are presented as examples to show that the same switch fabric can be reconfigured to perform different logic functions.
181 citations
TL;DR: In this article, the authors present an in-depth discussion of practical microring modulators in silicon, covering their performance metrics, design tradeoffs, optimization, p-n junction geometries, complex ring configurations, and tuning solutions.
Abstract: Silicon photonics is the most promising pathway to achieve >10 Tb/s off-chip I/O bandwidth required by next-generation high-performance computing and switching systems. Ring resonator modulators offer the advantages of small footprint, low power, high efficiency, low loss, high speed, and CMOS compatibility for silicon photonic links. This paper presents an in-depth discussion of practical microring modulators in silicon, covering their performance metrics, design tradeoffs, optimization, p-n junction geometries, complex ring configurations, and tuning solutions. Various demonstrated Si ring modulators are reviewed and potential future developments are briefly discussed.
164 citations
Cites background or methods from "Wavelength-tunable silicon microrin..."
...Asymmetric p-n junctions were used in some devices to improve performance [38]–[41], although the benefit is not signif-...
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...in [41]–[44] had integrated thermal tuning....
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...The thermal tuning solution is the one being pursued by many groups [34], [41], [42], [51] borrowing from earlier demonstrations made with silicon nitride ring filters and switches [93]....
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References
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TL;DR: In this article, a numerical Kramers-Kronig analysis is used to predict the refractive index perturbations produced in crystalline silicon by applied electric fields or by charge carriers.
Abstract: A numerical Kramers-Kronig analysis is used to predict the refractive-index perturbations produced in crystalline silicon by applied electric fields or by charge carriers. Results are obtained over the 1.0-2.0 \mu m optical wavelength range. The analysis makes use of experimental electroabsorption spectra and impurity-doping spectra taken from the literature. For electrorefraction at the indirect gap, we find \Delta n = 1.3 \times 10^{5} at \lambda = 1.07 \mu m when E = 10^{5} V/cm, while the Kerr effect gives \Delta n = 10^{-6} at that field strength. The charge-carrier effects are larger, and a depletion or injection of 1018carriers/cm3produces an index change of \pm1.5 \times 10^{-3} at \lambda = 1.3 \mu m.
2,502 citations
TL;DR: Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures, and here a high-speed electro-optical modulator in compact silicon structures is experimentally demonstrated.
Abstract: Metal interconnections are expected to become the limiting factor for the performance of electronic systems as transistors continue to shrink in size. Replacing them by optical interconnections, at different levels ranging from rack-to-rack down to chip-to-chip and intra-chip interconnections, could provide the low power dissipation, low latencies and high bandwidths that are needed. The implementation of optical interconnections relies on the development of micro-optical devices that are integrated with the microelectronics on chips. Recent demonstrations of silicon low-loss waveguides, light emitters, amplifiers and lasers approach this goal, but a small silicon electro-optic modulator with a size small enough for chip-scale integration has not yet been demonstrated. Here we experimentally demonstrate a high-speed electro-optical modulator in compact silicon structures. The modulator is based on a resonant light-confining structure that enhances the sensitivity of light to small changes in refractive index of the silicon and also enables high-speed operation. The modulator is 12 micrometres in diameter, three orders of magnitude smaller than previously demonstrated. Electro-optic modulators are one of the most critical components in optoelectronic integration, and decreasing their size may enable novel chip architectures.
2,336 citations
TL;DR: In this paper, the state-of-the-art CMOS silicon-on-insulator (SOI) foundries are now being utilized in a crucial test of 1.55mum monolithic optoelectronic (OE) integration, a test sponsored by the Defense Advanced Research Projects Agency (DARPA).
Abstract: The pace of the development of silicon photonics has quickened since 2004 due to investment by industry and government. Commercial state-of-the-art CMOS silicon-on-insulator (SOI) foundries are now being utilized in a crucial test of 1.55-mum monolithic optoelectronic (OE) integration, a test sponsored by the Defense Advanced Research Projects Agency (DARPA). The preliminary results indicate that the silicon photonics are truly CMOS compatible. RD however, lasing has not yet been attained. The new paradigm for the Si-based photonic and optoelectric integrated circuits is that these chip-scale networks, when suitably designed, will operate at a wavelength anywhere within the broad spectral range of 1.2-100 mum, with cryocooling needed in some cases
1,789 citations
TL;DR: An approach based on a metal–oxide–semiconductor (MOS) capacitor structure embedded in a silicon waveguide that can produce high-speed optical phase modulation is described and an all-silicon optical modulator with a modulation bandwidth exceeding 1 GHz is demonstrated.
Abstract: 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 photonics1. 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 compounds2,3,4,5,6 and/or electro-optic materials such as lithium niobate7,8,9. 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 structures12,13. 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.
1,612 citations
Journal Article•
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TL;DR: The silicon chip has been the mainstay of the electronics industry for the last 40 years and has revolutionized the way the world operates as mentioned in this paper, however, any optical solution must be based on low-cost technologies if it is to be applied to the mass market.
Abstract: The silicon chip has been the mainstay of the electronics industry for the last 40 years and has revolutionized the way the world operates. Today, a silicon chip the size of a fingernail contains nearly 1 billion transistors and has the computing power that only a decade ago would take up an entire room of servers. As the relentless pursuit of Moore's law continues, and Internet-based communication continues to grow, the bandwidth demands needed to feed these devices will continue to increase and push the limits of copper-based signaling technologies. These signaling limitations will necessitate optical-based solutions. However, any optical solution must be based on low-cost technologies if it is to be applied to the mass market. Silicon photonics, mainly based on SOI technology, has recently attracted a great deal of attention. Recent advances and breakthroughs in silicon photonic device performance have shown that silicon can be considered a material onto which one can build optical devices. While significant efforts are needed to improve device performance and commercialize these technologies, progress is moving at a rapid rate. More research in the area of integration, both photonic and electronic, is needed. The future is looking bright. Silicon photonics could provide low-cost opto-electronic solutions for applications ranging from telecommunications down to chip-to-chip interconnects, as well as emerging areas such as optical sensing technology and biomedical applications. The ability to utilize existing CMOS infrastructure and manufacture these silicon photonic devices in the same facilities that today produce electronics could enable low-cost optical devices, and in the future, revolutionize optical communications
1,479 citations