All-Optical Processing Based on a Logic xor Gate and a Flip-Flop Memory for Packet-Switched Networks

The routing functionality by all-optically interconnecting semiconductor-based all-optical logic gates and flip-flops is demonstrated in the frame of an all-optical label swapping (AOLS) network. We experimentally show that the output of the all-optical 2-bit correlator is capable of toggling the states of the integrated flip-flop every 2.5 ns via an adaptation stage. High extinction ratios are obtained at the output of the flip-flop, which can be used to feed a high-speed wavelength converter to complete the routing functionality of the AOLS node. The potential integration of these semiconductor optical amplifier integrated Mach-Zehnder interferometer-based devices make the proposed approach a very interesting solution for future packet switched optical networks.     

Bistability and optical switching in a polarization-bistable laserdiode

Dependences of the polarization-bistable condition on the coefficients of linear and nonlinear gains of a laser diode are analyzed, including S-shaped and pitchfork types of bistability, in the optical output versus injection current characteristics. Moreover, the steady-state and dynamic characteristics of the optical output for optical input are investigated, taking account of a detuning of incident optical beam from the cavity resonant frequency of a polarization-bistable laser diode, TE-TM polarization switching is shown to be attained in the optical output of the polarization-bistable laser diode in a very fast switching time less than a nanosecond by the application of TE and TM optical input pulses     

Lasers and Photodetectors in Europe

This paper reviews the European activities on fiber optic semiconductor devices for optical communication. Progress in the development of lasers, LED's, and photodetectors and also first attempts of monolithic integration are reported. Emphasis is put on materials and devices for the wavelength range of 1200-1600 nm and for high-speed transmission. Results of recent work are highlighted. So, for example, extremely high reliability and high optical output power of LED's and Fabry-Perot lasers have been achieved. MOCVD growth techniques are increasingly applied for device fabrication; for lasers, highly reproducible characteristics have been demonstrated. Development of dynamic singlemode lasers (DSM) is under progress with low threshold currents and good optical characteristics reported. First electrically tunable single-mode lasers and DSM lasers with parallel coupled cavities have been realized. Long wavelength p-i-n photodetectors have reached maturity. InGaAsP and CdHgTe avalanche photodiodes show excellent properties for high-speed long-haul transmission. First steps of monolithic integration of several optical and electrical functions have been made and specifically for p-i-n-FET combinations good results have been achieved. The plans of European PTT authorities to implement fiber optics in trunk lines and subscriber loops will further push the activities on optoelectronic device technology.     

Ultralow-threshold-current lasing in inversion channel lasers

A new regime of semiconductor laser operation was observed in quantum-well inversion channels of double heterostructure optoelectronic switches. The quantum-well active region operated with substantial excess negative charge imbalance due to the proximity of a high-density depleted donor charge sheet. Threshold current densities as low as 15 A/cm² in as-cleaved 400-μm-long devices were measured, and unusual high-frequency operation under low power operation was observed. These qualities may be of great significance for optical interconnections and optoelectronic integrated circuits     

Optoelectronic time-of-flight design and the demonstration of anall-optical, stored program, digital computer

The recent demonstration of an all-optical, stored-program, digital computer by our group focused on high-speed optoelectronic design. It was made possible by a new digital design method known as time-of-flight design. A rudimentary, but general-purpose, proof of principle computer was built, which is all-optical in the sense that all signals connecting logic gates and all memory are optical in nature. LiNbO₃ directional couplers, electrooptic switches, are used to perform logic operations. In addition to demonstrating stored program operation in an optoelectronic digital computer, the system demonstrated the feasibility of the new design method, which does nor use any flip-flops or other bistable devices for synchronization or memory. This potentially allows system clock rates of the same order as device bandwidth. This paper describes how the time-of-flight design method was motivated by the special properties of optoelectronic digital design. The basic principles of the method we employed will be discussed along with some of its potential advantages. The experimental work with digital optical circuits leading up to and including the stored program computer experiment will then be discussed. Finally, the future potential of time-of-flight design in high-bandwidth optoelectronic systems will be discussed     

An overview of optical device research in China

An overview of research activities in China on the following optical communications devices is presented: quantum-well semiconductor lasers; distributed feedback laser diodes; wideband, tunable, narrow-linewidth, external-cavity laser diodes, semiconductor and doped-fiber amplifiers; laser-diode-pumped solid state and single-crystal fiber lasers; doped fiber ring lasers, optical modulators; switches; bistable devices; experimental wavelength-division-multiplexed (WDM) systems; and time-division photonic switching systems. The most important of these technologies are highlighted with respect to demonstrated achievements in China. The potential uses of these technologies in future telecommunications systems are discussed     

Optoelectronic logic operations by cleaved-coupled-cavity semiconductor lasers

We propose and demonstrate the operation of a new opto-electronic scheme of performing the set of logic operations including AND, OR, EXCLUSIVE OR, and INVERTER. The present scheme is not based on optical bistability, but rather utilizes the unique characteristics of the newly developed cleaved-coupled-cavity (C³) semiconductor laser. The C³laser always operates in a single longitudinal mode and the lasing wavelength can be tuned by varying the current levels (pulsed or dc) injected into the two optically coupled stripe-geometry laser diodes. Unlike the case of optical bistable devices (based on FP semiconductor diodes), which operate on optical inputs and produce optical outputs, the present device operates on electrical inputs and produces optical outputs. In addition to performing the logic operations, this can also serve as an electrical-optical interface. Further, the present scheme is also capable of producing multiple different logic outputs simultaneously for the same two inputs. Results from time-resolved spectral measurements using InGaAsP buried crescent lasers (lambda = 1.3 mum) showed that the switching time was in the subnanosecond region. This indicates that extremely high bit rate information processing in the Gbit/s range can be achieved by using the present C³semiconductor lasers as the logic gates. The present C³lasers are very compact (sim300 times sim200 mum) and rigid, and the scheme can be applied to semiconductor lasers with other types of stripe geometries and wavelengths.     

自动交换光网络中光电子器件的进展

光网络正在向高速大容量、良好的扩展性和智能化的方向发展。自动交换光网络的出现是光传送网技术的重要突破,光电子器件功能的增强与性能的提高将对其实现与发展起决定性作用。本文介绍了自动交换光网络中一些光电子器件的重要特性和发展趋势。     

Recent developments in monolithic integration of InGaAsP/InP optoelectronic devices

Monolithically integrated optoelectronic circuits combine optical devices such as light sources (injection lasers and light emitting diodes) and optical detectors with solid-state semiconductor devices such as field effect transistors, bipolar transistors, and others on a single semiconductor crystal. Here we review some of the integrated circuits that have been realized and discuss the laser structures suited for integration with emphasis on the InGaAsP/InP material system. Some results of high frequency modulation and performance of integrated devices are discussed.     

Less than 10 ps optoelectronic switching by semiconductor injection lasers

The generation of electrical pulses was carried out with optoelectronic switches which were controlled by semiconductor injection lasers. Electrical pulses with rise times less than 10 ps were formed.<>     

Output characteristics of Nd:GdVO4 crystals laser with dual c-axis orthogonal gains end-pumped by two fiber- coupled diode lasers

The output characteristics of neodymium-doped gadolinium vanadate (Nd:GdVO4) crystals laser with dual c-axis orthogonal gains end-pumped by two fiber-coupled diode lasers are investigated. With two 1 W semiconductor diode lasers pumping, the output power of TEM00 laser is 920 mW, and the optical conversion efficiency is close to 46%. By changing the relative orientations of both Nd:GdVO4 crystals, the polarization characteristics of laser are varied. In particular, by keeping the c-axes of two Nd:GdVO4 crystals orthogonal to each other and adjusting two diode pump lasers to operate at the same power level, the completely unpolarized light is obtained.     

Advances in self-assembled semiconductor quantum dot lasers

In the past 20 years the semiconductor laser has become a key device in optical electronics because of its pure output spectrum and high quantum efficiency. As the capabilities of laser diodes have grown, so has the range of applications contemplated for them. A great success in semiconductor lasers has been brought by the ability to artificially structure new materials on an atomic scale by using advanced crystal growth methods such as MBE and MOVPE. The laser performance successes gained using quantum wells in optoelectronic devices can be extended by adopting quantum wire and quantum dot structures. There have been several reports of successful lasing action in semiconductor dot structures within the past few years. In this article I will briefly review the recent progress in the development of quantum dot lasers.     

Optoelectronic integration of a GaAs/AlGaAs bistable field effecttransistor (BISFET) and LED

The bistable field effect transistor (BISFET) is a novel inversion-channel switching device exhibiting abrupt current transitions and hysteresis in its output characteristics. The semiconductor structure of the BISFET is compatible with a range of electronic and optoelectronic devices. In this work, integration of a BISFET with an LED is reported. Both devices have been implemented on a single semiconductor substrate using a single fabrication sequence. The BISFET is used to current drive the LED. Abrupt transitions and hysteresis are seen in the optical output from the circuit in the range of gate voltage from 1.75 V to 1.9 V     

日本半导体光电子器件研究与开发的新进展

根据对日本九所研究所和大学的实地考察,综述了这些研究机构在光电子器件方面的研究和开发进展,这些光电器件主要包括多波长光源和滤长可选择光源、电吸收调制器与分布反馈激光器的集成、泵浦用大功率激光器、大功率ＧａＮ激光器和平面光波回路等。同时,介绍了日本半导体光电产业的发展现状和趋势。     

All-optical network subsystems using integrated SOA-based optical gates and flip-flops for label-swapped networks

In this letter, we demonstrate that all-optical network subsystems, offering intelligence in the optical layer, can be constructed by functional integration of integrated all-optical logic gates and flip-flops. In this context, we show 10-Gb/s all-optical 2-bit label address recognition by interconnecting two optical gates that perform xor operation on incoming optical labels. We also demonstrate 40-Gb/s all-optical wavelength-switching through an optically controlled wavelength converter, consisting of an integrated flip-flop prototype device driven by an integrated optical gate. The system-level advantages of these all-optical subsystems combined with their realization with compact integrated devices, suggest that they are strong candidates for future packet/label switched optical networks.     

Optically-cascaded, multistage switching operation of a multifunctional binary optical/optoelectronic switch

Optically cascadable and multifunctional binary optical switches consisting of AlGaAs-GaAs vertical cavity surface-emitting lasers (VCSELs), heterojunction bipolar transistors (HBTs), and p-i-n photodetectors (PINs) have been realized. Each switching element consists of a pair of PIN/HBT/VCSEL switches that can perform optical switching and routing at a data rate of 100 Mb/s, and optoelectronic signal conversion at a data rate of 100 Mb/s, while achieving a peak dc optical gain of 18 and an ac optical gain of 4. Optically-cascaded, multistage switching operation has been demonstrated using two linear arrays of HBT/PIN/VCSEL switches, with an overall cascaded dc optical gain of 50 and an ac gain of 8.     

Quantum wire lasers

Recent progress in the development of the concept and technology of semiconductor quantum wire (QWR) lasers is reviewed. In these quasi-one-dimensional structures, optical gain is provided by charge carriers that are quantum mechanically confined in two dimensions within wire-like active regions. These devices are expected to exhibit improved laser performance, including extremely low threshold currents (in the μA range), higher modulation bandwidth, narrower spectral linewidth, and reduced temperature sensitivity. QWR lasers would thus be particularly useful in applications involving densely packed laser arrays and monolithic integration of lasers with low-power electronics, including computer optical interconnects, optical computing, and integrated optoelectronic circuits. Approaches for fabricating these novel structures are reviewed, and recent successful demonstrations of lasing in semiconductor QWRs are described. Prospects for further progress in this area are also discussed     

Introduction to the special issue on strained-layer optoelectronicmaterials and devices

Strained layer quantum-well heterostructure semiconductor lasers and other optoelectronic devices are having an impact on nearly all applications of optoelectronics and especially fiber optic telecommunications. In this special issue on strained-layer optoelectronic materials and devices, the most recent advances in this fast-moving area of research are represented by 11 invited papers and 18 contributed papers. The research reported here covers an impressive range from detailed calculations and experimental data on the valence band structure and optical gain of strained layer heterostructures to the laser operating characteristics of devices made from these structures     

Metal Halide Perovskite Arrays: From Construction to Optoelectronic Applications

Inorganic semiconductor arrays revolutionize many areas of electronics, optoelectronics with the properties of multifunctionality and large-scale integration. Metal halide perovskites are emerging as candidates for next-generation optoelectronic devices due to their excellent optoelectronic properties, ease of processing, and compatibility with flexible substrates. To date, a series of patterning technologies have been applied to perovskites to realize array configurations and nano/microstructured surfaces to further improve device performances. Herein, various construction methods for perovskite crystal or thin film arrays are summarized. The optoelectronic applications of the perovskite arrays are also discussed, in particular, for photodetectors, light-emitting diodes, lasers, and nanogratings.     

Organic-on-organic semiconductor heterojunctions: building blockfor the next generation of optoelectronic devices

A novel class of optoelectronic devices utilizing thin films of stable crystalline organic semiconductors layered onto inorganic semiconductor substrates is described. The electrical properties of these devices are determined by the energy barrier at the heterojunction contact between the organic and inorganic materials, and in many ways are similar to those of ideal diffused-junction inorganic semiconductor devices. The organic materials can be layered onto semiconductor substrates without inducing large strains in either material, hence allowing a wide range of material combinations with a similarly broad range of optoelectronic functions to be realized. As examples, high-bandwidth photodetectors and field-effect transistors made using organic/inorganic semiconductor heterojunctions are discussed. Modification of the optical and electronic properties of the organic films by irradiation with energetic electron and ion beams is considered