Saturday, September 02, 2006

Gap structures and wave functions of classical waves in large-sized two-dimensional quasiperiodic structures

Y. Lai,1 Z. Q. Zhang,1 C. H. Chan,2 and L. Tsang2

1Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
2Department of Electronic Engineering, City University of Hong Kong, Kowloon, Hong Kong

(Received 8 May 2006; published 30 August 2006)

By using the sparse-matrix canonical-grid method, we performed large-scale multiple-scattering calculations to study the gap structures and wave functions of classical waves in two-dimensional quasiperiodic structures. We observed many interesting phenomena arising from the quasiperiodic long-range order. In particular, a self-similar wave function with resonant structures was observed at a band edge. Our findings indicate that two-dimensional quasiperiodic systems exhibit a universal behavior that applies to both electrons (or phonons) in discrete lattices and classical waves in continuous media.

URL: http://link.aps.org/abstract/PRB/v74/e054305

doi:10.1103/PhysRevB.74.054305

PACS: 71.23.Ft, 43.40.+s, 42.70.Qs, 61.44.Br


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Excitation wavelength dependence of terahertz emission from semiconductor surface

Masato Suzuki and Masayoshi Tonouchi
Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871, Japan
Ken-ichi Fujii
Department of Physics, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan
Hideyuki Ohtake and Tomoya Hirosumi
Aisin Seiki Co., Ltd., Kojiritsuki, Hitotsugi-cho, Kariya 448-0003, Japan

(Received 30 January 2006; accepted 1 July 2006; published online 30 August 2006)

The authors have measured terahertz radiation from InSb, InAs, and InGaAs excited by femtosecond optical pulses at wavelengths of 1560, 1050, and 780 nm. The amplitude of the terahertz field strongly depends on the pump wavelengths. Among the materials, the InSb emitter shows the largest terahertz emission amplitude at high power 1560 nm excitation, whereas 780 nm excitation provides the weakest. With increasing photon energy, the increase in emission amplitude from InAs is less as compared to that from InGaAs. The decrease from InSb and InAs originates in low mobilities of L or X valley carriers generated by intervalley scatterings. ©2006 American Institute of Physics


doi:10.1063/1.2338430

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'Lumalive' textile presents variable LED display

A novel display-embedded textile from Philips Research can turn clothes into walking dynamic advertisements.

Philips Research, Eindhoven, Netherlands, is expecting to impress visitors at this year's IFA show (Internationale Funkausstellung, 1-6 September, Berlin, Germany) with the world's first demonstration of promotional jackets and furniture featuring the company's Lumalive technology.

Lumalive textiles allow the creation of fabrics that can carry dynamic advertisements, graphics and constantly changing color surfaces. Philips stand at the IFA show in Hall 22 will be a showcase for Lumalive textile products that will be worn by Philips' staff and embedded into booth furniture of the "Future Zone".

Although the technology has been developed only recently -early prototypes were exhibited at IFA 2005- Philips Research has made progress in fully integrating Lumalive fabrics into garments. The first-generation jackets are ready for commercialization by companies partnering with Philips Research, particularly those in the promotional industry looking for a new, high-impact medium.

Lumalive fabrics feature flexible arrays of colored LEDs integrated into the fabric - without compromising the softness or flexibility of the cloth. The light emitting textiles can carry dynamic messages, graphics or multicolored surfaces. Fabrics such as drapes, cushions or sofa coverings become active when they illuminate in order to enhance the observer's mood and positively influence his/her behavior.

The jackets are said to be comfortable to wear, and the Lumalive fabrics only become obvious when they light up to display various vivid colored patterns, logos, short text messages or even full color animations.

The electronics, batteries and LED arrays are fully integrated and invisible to the observer and wearer. The jackets feature panels of up to 200x200 mm2, although the active sections can be scaled up to cover much larger areas such as a sofa.

"Taking the Lumalive fabrics from prototypes to integrated products has been a major challenge," said Bas Zeper, managing director of Photonic Textiles, Philips Research. "The light emitting textiles have to be flexible, durable and operated by reasonably compact batteries. Fitting all that into a comfortable, lightweight garment is a considerable engineering success."

"Last year Philips Research showed our research prototypes; this year the jackets and furniture represent versions that are ready to go into commercial production, and include integrated power sources and control electronics," added Zeper.

The products include features that make them practical for daily use. For example, when integrating the Lumalive fabrics into the garment, Philips Research has made the parts that can't be easily washed - such as the batteries and control electronics-simple to disconnect and reconnect after the garment has been cleaned. Even the light-emitting layer can be easily removed and refitted to the jacket.

Philips Research is inviting potential partners to discuss the commercialization potential of the material at IFA 2006 where the company's booth is acting as a showcase for the technology and a focal point for discussions.

About the author

Matthew Peach is a contributing editor to optics.org and Optics & Laser Europe


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Luxtera claims first single chip dual XFP transceiver

Will permit economically-feasible fiber-to-chip connectivity. Technology is "the future" of optical interfaces, developer claims.

Luxtera, based in Carlsbad, Ca, US, a developer of CMOS photonic technology has announced a single-chip integrated photonics-electronics device implemented in a standard CMOS process.

The technology integrates high-performance optics and mainstream electronics on a single die, bringing fiber connectivity directly to a chip.

"Fabrication in a standard, high volume 0.13 micron SOI-CMOS process makes fiber optics feasible and economical for everyday applications," the company states. Additional digital logic can be integrated into the same chip with optical devices, reducing both device size and power consumption.

The technology incorporates two lasers and photodetectors mounted directly on a monolithic CMOS die that also includes all logic equivalent to two complete XFP modules including TransImpedance Amplifiers (TIA), Mach-Zehnder modulators, as well as transmit and receive Clock and Data Recovery (CDR) circuits. This complete single chip solution is one-quarter the size of existing XFP module solutions.

Luxtera is currently sampling prototype devices for preliminary testing by strategic development partners. The company will launch a commercial transceiver product line based on the technology early in 2007.

Initial product offerings will comprise multi-port transceivers for communications, storage, and computing applications.

The first commercial application is expected to be high speed, high bandwidth enterprise data communications. Driven by the high bandwidth capabilities of new multi-core, high performance processors, the need for low cost, low latency and low power 10G, and faster interconnects is here, the company adds.

"The potential impact on the industry of combining photonic and electronic elements on a single CMOS die is substantial," said Lawrence Gasman, president of CIR. "Many applications, including those in the cost sensitive consumer markets, will benefit from the improvements in cost, power consumption and size."

"CMOS Photonics technology will enable the widespread adoption of 10G interconnects, which today are very expensive to deploy, by driving the cost of 10G optical ports to well below $100."

As a result of Luxtera's technology, the cost of optical interfaces are reaching those of copper with the added benefits of lower power, lower latency, smaller footprint, longer reach and less expensive cabling. For complete link solutions, the technology provides 7X power reduction, 40X reach, 100X lower latency with scalability to 1000X the bandwidth of 10GBASE-T.

"This technology is the future of optical interfaces," said Marek Tlalka, vice president of marketing at Luxtera. "Traditional discrete optical solutions are bulky and costly. Emerging 10G copper interfaces are also bulky, power hungry and extremely limited in their reach. Our advanced developments eliminate these constraints to commercialization and, for the first time, render fiber optic performance at costs associated with copper interfaces a reality."

About the author

Matthew Peach is a contributing editor to optics.org and Optics & laser Europe.


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High output RGB sources promise laser TV 'by 2007'

Novalux says its new 750 mW red "Necsel" laser and 3 W green and blue models are paving the way for laser projection TV.

Novalux, Sunnyvale, Ca, has demonstrated its first Necsel laser arrays that emit more than 750 mW of red light. The company has also achieved a 3 W power output from its prototype blue and green arrays - double the power of previous devices.

The company says that these developments put Novalux on track to produce RGB (red, green, blue) Necsel lasers for integration into laser-based projection TVs.

"Demonstrating 750-mW red Necsel arrays, along with meeting our 3 W target for green and blue, are significant milestones in our evolution," said Greg Niven, Novalux's VP marketing. "Our customers want all-Necsel RGB devices for incorporation into laser-based home cinema systems."

"Ultimately, this means 3 W per colour. Now that we've met the target with green and blue, red isn't far behind and will soon be at the same level. We're on track to support the TV companies' desire to be selling high-definition laser TVs featuring Necsel laser color by Christmas 2007."

Novalux say that Necsel RGB sources benefit TV manufacturers over other types of laser because they provide desirable output wavelengths and can cut overall system cost. Specifically, red Necsel arrays produce light at 620 nm - a wavelength that matches existing TV-screen phosphors.

Competing red edge-emitter laser technology can only go as low as 635 nm and has poor lifetime. In a Necsel system the same type of laser emits each of the three colors so they share the same device parameters. This uniformity results in simpler, more cost-efficient laser integration from drive electronics to imaging optics.

Novalux's prototype Necsel devices emit 3 W at 465 nm and 532 nm and 750nbsp;mW at 620 nm - all from a new package smaller than a matchbox. Necsel lasers' output is bright, speckle-free, and color-saturated, giving in clear, vibrant images that reach a larger color space than competing lighting technologies.

Novalux first introduced concept Necsel-based RPTVs during the 2006 Consumer Electronics Show (CES). These early units demonstrated the expanded color range and striking image contrast.

The company's latest prototypes, shown during Society for Information Display (SID) 2006, demonstrated even higher brightness, color-balanced, speckle-free, high-definition images on 52 inch screens. Ultimately, Novalux aims to enable home theater systems that marry over 200% of NTSC color coverage, high-brightness, high-resolution images, a thin, wide viewing angle architecture, and unsurpassed light source lifetime.

About Novalux

Founded in 1998, Novalux has developed proprietary Necsel (Novalux Extended Cavity Surface Emitting Laser) technology. This combines mass volume manufacturability with excellent optical performance. Necsel device attributes include bright, reliable, consistent, speckle-free light output from a compact, low-cost package, making them ideal for current- and next-generation display applications.

About the author

Matthew Peach is a contributing editor to optics.org and Optics & Laser Europe


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