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We report a surface-normal optically controlled waveguide switch made of a p-i-n diode that utilizes optically induced voltage screening to turn on and diffusive conduction to turn off. We examine theoretically diffusive conduction in these switches and show that this mechanism offers the possibility of creating optical switches operating at several tens of GHz. As a proof-of-concept demonstration, we present experimental results of wavelength-converting, optical switching at frequencies up to 2.5 GHz in a multiple-quantum-well, GaAs-based waveguide device using milliwatt-level switching powers. Optimized arrays of these devices can be used for high-speed, multichannel wavelength conversion and optical regeneration in wavelength-division-multiplexed systems. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Germanium (Ge) and silicon-germanium (Si-Ge) have the potential to integrate optics with Si IC technology. The quantum-confined Stark effect, a strong electroabsorption mechanism often observed in III-V quantum wells (QWs), has been demonstrated in Si-Ge/Ge QWs, allowing optoelectronic modulators in such group IV materials. Here, based on photocurrent electroabsorption experiments on different samples and fitting of the resulting allowed and nominally forbidden transitions, we propose more accurate values for key parameters such as effective masses and band offsets that are required for device design. Tunneling resonance modeling including conduction band nonparabolicity was used to fit the results with good consistency between the experiments and the fitted transitions. [ABSTRACT FROM PUBLISHER]

A low-voltage, 90-nm CMOS optical interconnect transceiver operating at 1550-nm optical wavelength is presented. This is the first demonstration of a novel optoelectronic modulator architecture (the quasi-waveguide angled-facet electroabsorption modulator) in a system. It features a simple electronic packaging via flip-chip bonding to silicon. Devices have a broad optical bandwidth, are arrayed two dimensionally, and feature surface normal, spatially separated, and misalignment-tolerant optical ports. The modulators are driven with a novel pulsed-cascode driver capable of supplying an output-voltage swing of 2 V (twice the nominal 1-V CMOS supply) without overstressing thin-oxide core CMOS devices. At the receiver side, a sensitivity of -15.2 dBm is obtained with an integrating/double-sampling front end. The transceiver includes clock generation and recovery circuitry that enables a data serialization factor of five. At a maximum data rate of 1.8 Gb/s, the optical transmitter, receiver, and clocking circuitry consume 12.6, 4.5, and 6.5 mW, respectively, for a total link electrical power dissipation of 23.6 mW. To the best of our knowledge, this is the first demonstration of an interconnect transceiver operating at 1550 nm with a III-V output device directly integrated to the CMOS. [ABSTRACT FROM PUBLISHER]

We monolithically integrated polycrystalline GaAs metal-semiconductor-metal (MSM) photoconductive switches with a completely fabricated Si-CMOS amplifier and obtained a properly functional optical receiver, without altering the Si circuit performance. To our knowledge, this is the first time a fully monolithic on-chip integration has been achieved. [ABSTRACT FROM PUBLISHER]

In this paper, we introduce a robust monolithic integration technique for fabricating photonic integrated circuits comprising optoelectronic devices (e.g., surface-illuminated photodetectors, waveguide quantum-well modulators, etc.) that are made of completely separate epitaxial structures and possibly reside at different locations across the wafer as necessary. Our technique is based on the combination of multiple crystal growth steps, judicious placement of epitaxial etch-stop layers, a carefully designed etch sequence, and self-planarization and passivation steps to compactly integrate optoelectronic devices. This multigrowth integration technique is broadly applicable to most III-V materials and can be exploited to fabricate sophisticated, highly integrated, multifunctional photonic integrated circuits on a single substrate. As a successful demonstration of this technique, we describe integrated photonic switches that consume only a 300 ×300 μm footprint and incorporate InGaAs photodetector mesas and InGaAsP/InP quantum-well modulator waveguides separated by 50 μm on an InP substrate. These switches perform electrically-reconfigurable optically-controlled wavelength conversion at multi-Gb/s data rates over the entire center telecommunication wavelength band. [ABSTRACT FROM PUBLISHER]

We present a surface-normal modulator architecture for optical interconnects that offers misalignment tolerance as well as high contrast ratio over a wide wavelength range for a small drive voltage. A contrast ratio greater than 3 dB was achieved for only 0.8-V drive across a 16-nm wavelength range from 1498 to 1514 nm. The misalignment tolerance between this device, and the input optical beam was measured to be 30 μm. [ABSTRACT FROM PUBLISHER]

A novel electrically controlled tunable metal-semiconductor-metal (MSM) photodetector is introduced and experimentally demonstrated with 2.5-ns wavelength-switching access time on a GaAs chip for switching between two wavelengths. This detector has a demonstrated 20.1-dB ON/OFF contrast ratio between the selected and the rejected wavelength and can resolve 179-GHz spaced wavelength-division multiplexing channels. In addition, device wavelength switching is achieved with a differential input voltage swing of ±1.65 V. This low bias voltage makes it compatible with complementary metal-oxide semiconductor (CMOS) control electronics for rapid switching. [ABSTRACT FROM PUBLISHER]

Traditional optical-electronic-optical (o-e-o) conversion in today's optical networks requires cascading separately packaged electronic and optoelectronic chips and propagating high-speed electrical signals through and between these discrete modules. This increases the packaging and component costs, size, power consumption, and heat dissipation. As a remedy, we introduce a novel, chip-scale photonic switching architecture that operates by confining high-speed electrical signals in a compact optoelectronic chip and provides multiple network functions on such a single chip. This new technology features low optical and electrical power consumption, small installation space, high-speed operation, two-dimensional scalability, and remote electrical configurability. We present both theoretical and experimental discussion of our monolithically integrated photonic switches that incorporate quantum-well waveguide modulators directly driven by on-chip surface-illuminated photodetectors. These switches can be conveniently arrayed two-dimensionally on a single chip to realize a number of network functions. Of those, we have experimentally demonstrated arbitrary wavelength conversion across 45 nm and dual-wavelength broadcasting over 20 nm, both spanning the telecommunication center band (1530-1565 nm) at switching speeds up to 2.5 Gb/s. Our theoretical calculations predict the capability of achieving optical switching at rates in excess of 10 Gb/s using milliwatt-level optical and electrical switching powers. [ABSTRACT FROM PUBLISHER]

This paper proposes the use of shorter wavelengths and monolithic integration for chip-to-chip and on-chip optical communication. The promise of monolithic detectors for high-speed interconnection is demonstrated through experimental measurements and matching simulations. Responsivities >0.06 A/W and transit-time-limited response can be expected in the blue from planar p-i-n silicon-on-insulator (SOI) detectors. [ABSTRACT FROM PUBLISHER]

This paper demonstrates the use of a single multilayer thin-film stack for generating custom-engineered spatial dispersion, i.e., spatial shift as a function of wavelength. Based on group-velocity effects similar to the superprism effect observed in photonic crystals, this thin-film grating (TFG) device allows for multiplexing or demultiplexing multiple wavelength-division-multiplexed (WDM) channels using a single nonperiodic thin-film stack. We designed a four-channel TFG for coarse WDM applications with 20-nm channel spacing and flat-top passbands. This paper shows that flat-top passbands correspond to a steplike spatial beam shifting with wavelength. The influence of a finite beamwidth on the passband shape is discussed using Fourier decomposition of the beam into plane-wave components. The paper concludes with experimental results for a three-channel TFG demonstrating steplike beam shifting. [ABSTRACT FROM PUBLISHER]

By linking the unique capabilities of photonic devices with the signal processing power of electronics, photonically sampled analog-to-digital (A/D) conversion systems have demonstrated the potential for superior performance over all-electrical A/D conversion systems. We adopt a photonic A/D conversion scheme using low-temperature (LT)-grown GaAs metal-semiconductor-metal (MSM) photoconductive switches integrated with Si-CMOS A/D converters. The large bandwidth of the LT GaAs switches and the low timing jitter and short width of mode-locked laser pulses are combined to accurately sample input frequencies up to several tens of gigahertz. CMOS A/D converters perform back-end digitization, and time-interleaving is used to increase the total sampling rate of the system. In this paper, we outline the development of this system, from optimization of the LT GaAs material, speed and responsivity measurements of the switches, bandwidth and linearity characterization of the first-stage optoelectronic sample-and-hold, to integration of the switches with CMOS chips. As a final proof-of-principle demonstration, a two-channel system was fabricated with LT GaAs MSM switches flip-chip bonded to CMOS A/D converters. When operated at an aggregate sampling rate of 160 megasamples/s, the prototype system exhibits ∼3.5 effective number of bits (ENOB) of resolution for input signals up to 40 GHz. [ABSTRACT FROM PUBLISHER]

We demonstrate operation of a wavelength division multiplexed chip-to-chip optical interconnect using surface-normal electroabsorption modulators, and a modelocked laser as a single broadband source. The link was successfully operated at 80 Mb/s. While this rate was limited by the repetition rate of the modelocked source, individual CMOS circuits and optoelectronic devices have been shown to work at data rates approaching 1 Gb/s. [ABSTRACT FROM PUBLISHER]

Many properties of an optically interconnected system can be improved through the use of a modelocked laser. The short pulse duration, high peak power, wide spectral bandwidth, and low timing jitter of such a laser lead to these benefits. Timing advantages include simplified synchronization across large chip areas, receiver latency reduction, and data resynchronization. Lower power dissipation may be achieved through improved receiver sensitivity. Additional applications of short optical pulses include time-division multiplexing, single-source wavelength-division multiplexing, and precise time-domain testing of circuits. Several of these concepts were investigated using a high-speed chip-to-chip optical interconnect demonstration link. The link employs a modelocked laser and surface-normal optoelectronic modulators that were flip-chip bonded to silicon CMOS circuits. This paper outlines experiments that were performed on or simulated for the link, and discusses the important benefits of ultrashort optical pulses for optical interconnection. [ABSTRACT FROM PUBLISHER]

We present a new method of latency reduction in optical interconnects: using very low duty cycle return-to-zero encoding (i.e., subpicosecond pulses). An analytical comparison of three different receiver architectures, including transimpedance, integrating, and totem-pole diode pair, is presented. For all three receivers, we demonstrate that using short pulses instead of nonreturn-to-zero (NRZ) shortens the circuit delay. We also experimentally demonstrate a ∼65% reduction in latency of a transimpedance receiver by using short optical pulses. Finally, we show that the latency of optical interconnects can be comparable to or even less than electrical interconnects for global on-chip communication. [ABSTRACT FROM PUBLISHER]

We present a new technique of injecting clocks optically onto CMOS chips without the use of a receiver amplifier. We discuss the benefits of such a direct approach and present proof-of-principle experiments of the technique. We analytically compare a receiver-less optical clock distribution and an electrical clock distribution in a fan-out-of-four clock tree to evaluate the timing and power benefits of the optical approach for present microprocessors. We also compare receiver-less direct injection of optical clocks to trans-impedance receiver based injection within the same distribution framework. [ABSTRACT FROM PUBLISHER]

We report a novel, miniature Fourier transform spectrometer with a linear architecture that works by sampling a standing wave. The spectrometer consists of an electrostatically actuated microelectromechanical mirror with on-resonance displacement of up to 65 μm, a thin-film photodetector, and an electrical back plane for actuating the mirror. The integrated device offers mirror stability and fixed relative alignment of the three components. The spectrometer has better than 32-nm resolution at 633 nm [ABSTRACT FROM PUBLISHER]

This paper gives a brief historical summary of the development of the field of optical interconnects to silicon integrated circuits. It starts from roots in early optical switching phenomena, proceeds through novel semiconductor and quantum well optical and optoelectronic physics and devices, first proposals for optical interconnects, and optical computing and photonic switching demonstrators, to hybrid integrations of optoelectronic and silicon circuits that may solve basic scaling and other problems for interconnections in future information processing and switching machines [ABSTRACT FROM PUBLISHER]

Quantum well semiconductor structures allow small, fast, efficient optoelectronic devices such as optical modulators and switches. These are capable of logic themselves and have good potential for integration with electronic integrated circuits for parallel high speed interconnections. Devices can be made both in waveguides and two-dimensional parallel arrays. Working arrays of optical logic and memory devices have been demonstrated, to sizes as large as 2 048 elements, all externally accessible in parallel with free-space optics. This article gives an overview of the physics underlying the operation of such devices, and describes the principles of several of the device types, including self-electrooptic effect devices (SEEDs). [ABSTRACT FROM AUTHOR]