Plasma-induced quantum well intermixing for monolithic photonic integration

Plasma-induced quantum well intermixing (QWI) has been developed for tuning the bandgap of III-V compound semiconductor materials using an inductively coupled plasma system at the postgrowth level. In this paper, we present the capability of the technique for a high-density photonic integration process, which offers three aspects of investigation: 1) universality to a wide range of III-V compound material systems covering the wavelength range from 700 to 1600 nm; 2) spatial resolution of the process; and 3) single-step multiple bandgap creation. To verify the monolithic integration capability, a simple photonic integrated chip has been fabricated using Ar plasma-induced QWI in the form of a two-section extended cavity laser diode, where an active laser is integrated with an intermixed low-loss waveguide.     

Design of high-Q microcavities for proposed two-dimensional electrically pumped photonic crystal lasers

Electrically pumped photonic crystal lasers are of practical importance for future integrated photonic circuit systems. This paper proposes a methodology for achieving high quality (Q) factor photonic crystal defect cavities that allow current injection into their active regions. It is shown that by combining certain high Q-factor photonic crystal cavity designs with the technique of wet oxidation of (Al,Ga)As layers, Q factors of up to /spl sim/10/sup 4/ can be obtained within the scope of existing semiconductor planar process technology. The proposed device structures can be optimized through use of finite-difference time-domain methods to obtain optimal separation of the high refractive index substrate from the active core; furthermore, the effects of the top ohmic contact layer, the top and bottom cladding layers of the structure, and the current injection opening can be taken into account to achieve an optimal Q factor in electrically pumped lasers.     

Intimate monolithic integration of chip-scale photonic circuits

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 /spl times/300 /spl mu/m footprint and incorporate InGaAs photodetector mesas and InGaAsP/InP quantum-well modulator waveguides separated by 50 /spl mu/m 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.     

Label recognition using collinear acoustooptic devices in WDM photonic router

Collinear acoustooptic (AO) switches are investigated for use in label recognition system in photonic routing systems. The optical label discussed in this paper uses optical codes which are encoded in the time domain. Short optical pulse trains representing the codes are processed with integrated AO devices. Proposed device configurations for label recognition are described with the basic operation mechanism. A numerical example for the code recognition is also presented. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(3): 48–55, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20453     

Intelligence and security informatics for homeland security: information, communication, and transportation

Intelligence and security informatics (ISI) is an emerging field of study aimed at developing advanced information technologies, systems, algorithms, and databases for national- and homeland-security-related applications, through an integrated technological, organizational, and policy-based approach. This paper summarizes the broad application and policy context for this emerging field. Three detailed case studies are presented to illustrate several key ISI research areas, including cross-jurisdiction information sharing; terrorism information collection, analysis, and visualization; and "smart-border" and bioterrorism applications. A specific emphasis of this paper is to note various homeland-security-related applications that have direct relevance to transportation researchers and to advocate security informatics studies that tightly integrate transportation research and information technologies.     

A quantum-well-intermixing process for wavelength-agile photonic integrated circuits

Wavelength-agile photonic integrated circuits are fabricated using a one-step ion implantation quantum-well intermixing process. In this paper, we discuss, the issues in processing optimized widely tunable multisection lasers using this technique and present the results achieved using this process. This quantum-well intermixing process is general in its application and can be used to monolithically integrate a wide variety of optoelectronic components with widely tunable lasers.     

Optical modeling of waveguide photonic nanostructures using theradiation spectrum method (RSM) with evanescent modes

In this work, we study the effects of the evanescent modes in the simulation and modeling of optical integrated circuits based on photonic bandgap structures. We show that the contribution of these modes in the energy transfer in structures like the MOEM structures, can not be neglected. The radiation spectrum method, recently developed by the authors for the guided wave devices, is thus extended to account for the evanescent mode propagation. Applying this technique on an air-gap in a suspended waveguide a model of this gap is developed in terms of its parameters. This model is then integrated in an all optical simulator to predict the performance of photonic structures. Such technique enables to design and to optimize the photonic integrated circuits taking the evanescent modes effects into account     

Photonic Crystal and Plasmonic Silicon-Based Light Sources

Efficient silicon (Si)-compatible emitters can realize inexpensive light sources for a variety of applications. In this paper, we study both photonic crystal (PC) and plasmonic nanocavities that enhance the emission of Si-compatible materials. In particular, we examine the coupling of silicon nanocrystals (Si-NCs) to silicon nitride PC cavities and Si-NCs in silicon dioxide to plasmonic gratings, both for enhancement of emission in the visible wavelengths. In addition, we also observe the enhancement of the 1530 nm emission from erbium-doped silicon nitride films coupled to Si PC cavities. Finally, we analyze the loss mechanisms associated with the hybrid silicon nitride/silicon system, and propose advancements in the designs of PC and plasmonic cavities for the emitters described in this paper.      

Progress in InGaAs-GaAs selective-area MOCVD toward photonicintegrated circuits

The progress toward integrated photonic devices by selective-area metalorganic chemical vapor deposition (MOCVD) is reviewed. Processing steps involved with fabricating buried heterostructures (BHs) by a three-step technique are outlined, and a computational model is presented that predicts the enhancement behavior of selective-area MOCVD. Results are reviewed for several discrete and integrated photonic devices. These include low-threshold BH lasers, laser diodes integrated with either intracavity or external cavity modulators, dual-channel emitters integrated with both modulators and passive y-junction waveguides, and broad-band light-emitting diodes (LEDs)     

Modelling PBG devices to DWDM filters design

The fibre optic transmission systems require a bandwidth of about 25 THz in telecommunications networks, for which it is necessary to resort to dense wavelength division multiplexing (DWDM) systems. These systems need optical filters to broadcast selectively or not in a given wavelength band. A new very promising technology for these applications is the photonic crystals with forbidden bandgap (photonic bandgap (PBG)). In this paper, we propose a model of PBG devices to design DWDM filters on PBG materials. Copyright © 2004 John Wiley & Sons, Ltd.     

Advances in silicon-on-insulator optoelectronics

Recent developments in silicon based optoelectronics relevant to fiber optical communication are reviewed. Silicon-on-insulator photonic integrated circuits represent a powerful platform that is truly compatible with standard CMOS processing. Progress in epitaxial growth of silicon alloys has created the potential for silicon based devices with tailored optical response in the near infrared. The deep submicrometer CMOS process can produce gigabits-per-second low-noise lightwave electronics. These trends combined with economical incentives will ensure that silicon-based optoelectronics will be a player in future fiber optical networks and systems     

Optoelectronic-VLSI: photonics integrated with VLSI circuits

Optoelectronic-VLSI (OE-VLSI) technology represents the intimate integration of photonic devices with silicon VLSI electronics. We review the motivations and status of emerging OE-VLSI technologies and examine the performance of OE-VLSI technology versus conventional wire-bonded OE packaging. The results suggest that OE-VLSI integration offers substantial power and speed improvements even when relatively small numbers of photonic devices are driven with commodity complementary metal-oxide-semiconductor logic technologies     

Power electronics and future marine electrical systems

Tomorrow's marine electrical systems will be profoundly different from today's systems. Power electronics is making major impacts on virtually every marine system including propulsion, power distribution, auxiliaries, sonar, and radar. Newly emerging materials, components, and system concepts (such as wide band-gap materials, silicon-carbide-based power semiconductor devices, power electronics building blocks (PEBBs), and integrated power systems) are, and will continue, enabling future marine systems as different from today's systems as steam ships were to sailing ships. However, these enabling technologies and concepts are not well known and have been difficult to understand. This paper will introduce these new concepts and technologies, identify potential impacts, and explore new design methods to simplify marine electrical system development.     

电力电子和未来的航海电气系统(上)

明天的航海电气系统将同今天的系统有极大的不同。电力电子给予船舶上包括推进、电力分配、备用电源、声纳和雷达等在内的各种系统的进展以重要的影响。刚刚出现的新材料、新器件和新的系统概念(诸如宽带半导体材料、碳化硅基的电力半导体器件、电力电子模组(PEBB),以及集成功率系统)正在使、并将持续地使未来的航海系统有别于今天的系统,如同内燃船舶有别于蒸汽船舶。但是,这些正在实现的技术和有关概念还未被大家所周知,而且还有难于理解的地方。本文就将介绍这些新概念和新技术,指出潜在的影响力,并揭示新的设计方法,以推动航海电气系统的发展。     

Monolithic integration via a universal damage enhanced quantum-wellintermixing technique

A novel technique for quantum-well intermixing is demonstrated, which has proven a reliable means for obtaining postgrowth shifts in the band edge of a wide range of III-V material systems. The technique relies upon the generation of point defects via plasma induced damage during the deposition of sputtered SiO₂, and provides a simple and reliable process for the fabrication of both wavelength tuned lasers and monolithically integrated devices. Wavelength tuned broad area oxide stripe lasers are demonstrated in InGaAs-InAlGaAs, InGaAs-InGaAsP, and GaInP-AlGaInP quantum well systems, and it is shown that low absorption losses are obtained after intermixing. Oxide stripe lasers with integrated slab waveguides have also enabled the production of a narrow single lobed far field (3°) pattern in both InGaAs-InAlGaAs, and GaInP-AlGaInP devices. Extended cavity ridge waveguide lasers operating at 1.5 μm are demonstrated with low loss (α=4.1 cm^-1) waveguides, and it is shown that this loss is limited only by free carrier absorption in waveguide cladding layers. In addition, the operation of intermixed multimode interference couplers is demonstrated, where four GaAs-AlGaAs laser amplifiers are monolithically integrated to produce high output powers of 180 mW in a single fundamental mode. The results illustrate that the technique can routinely be used to fabricate low-loss optical interconnects and offers a very promising route toward photonic integration     

Raman-based silicon photonics

This paper reviews recent progress in a new branch of silicon photonics that exploits Raman scattering as a practical and elegant approach for realizing active photonic devices in pure silicon. The large Raman gain in the material, enhanced by the tight optical confinement in Si/SiO2 heterostructures, has enabled the demonstration of the first optical amplifiers and lasers in silicon. Wavelength conversion, between the technologically important wavelength bands of 1300 and 1500 nm, has also been demonstrated through Raman four wave mixing. Since carrier generation through two photon absorption is omnipresent in semiconductors, carrier lifetime is the single most important parameter affecting the performance of silicon Raman devices. A desired reduction in lifetime is attained by reducing the lateral dimensions of the optical waveguide, and by actively removing the carriers with a reverse biased diode. An integrated diode also offers the ability to electrically modulate the optical gain, a unique property not available in fiber Raman devices. Germanium-silicon alloys and superlattices offer the possibility of engineering the otherwise rigid spectrum of Raman in silicon.     

A high-speed 32-channel CMOS VCSEL driver with built-in self-testand clock generation circuitry

This paper describes the design, electrical, and optical test results for a high-speed 32-channel CMOS vertical-cavity surface emitting laser (VCSEL) driver integrated circuits with built-in self-test and clock generation circuitry. The circuit design and silicon parts are available to the research community through the Consortium for Optical and Optoelectronic Technologies in Computing (CO-OP) and the Optoelectronics Industry Association (OIDA). This device is specifically targeted at users building VCSEL-based smart photonic system demonstrators. A ten-channel version of this driver chip is also available with the same functionality and performance     

Analysis of Hybrid Dielectric Plasmonic Waveguides

Future ultracompact photonic integrated circuits (PICs) will rely on high-index-contrast dielectric materials, which permit a strong confinement of the optical field in the diffraction limit as well as low propagation losses. This is the case of PICs implemented on a silicon-on-insulator (SOI) platform. To achieve confinement beyond the diffraction limit, plasmonic waveguides (based on metal–dielectric interfaces) have been recently proposed. This new kind of waveguide provides a strong enhancement of the field in the metal–dielectric interface, which is of paramount importance for nonlinear functionalities or sensing. Plasmonic waveguides can also be built on SOI wafers. Thus, it can be reasonably thought that high index contrast as well as plasmonic waveguides can coexist in future ultradense PICs. In this paper, a theoretical and numerical study on the performance of several dielectric and plasmonic waveguides is presented. Thanks to their plasmon-coupled supported modes, ultracompact devices as hybrid ring resonators can be devised and integrated with silicon photonic circuits.      

3-D photonic circuit technology

Vertically coupled, wafer-bonded III-V semiconductor waveguide devices provide a means to obtain more powerful, compact photonic integrated circuits and allow for the combination of different materials onto a single chip. Various switching, filtering, multiplexing, and beam splitting devices in the InP-InGaAsP and GaAs-AlGaAs systems for signals in the 1550-nm range have been realized. An investigation of optimal optical add-drop multiplexer waveguide layout shapes has been performed through integration of the coupled-mode Riccati equation, providing potential sidelobe levels of less than -32 dB and filter bandwidths over 20% narrower than those of previous devices. Effects of nonideal processing conditions on filter performance are analyzed as well.