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PI Physik Instrumente - Revolution In Photonics Align LW LB 3/24

Silicon Emits Visible Light

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A surprising sparkle of green light from a silicon chip has opened up a field of possibilities for communications devices, including exponentially shrinking the hardware needed for high-quality Internet connections.

“When I saw the green light on the camera, I was extremely puzzled,” said Dr. Christian Grillet of the University of Sydney. “We were using infrared light, not green. And besides, silicon does not transmit light at that wavelength!”

Grillet’s colleague, Dr. Christelle Monat, was in the labs of CUDOS (Centre for Ultrahigh Bandwidth Devices for Optical Systems) in the school of physics at the time. “I didn’t believe the camera. I had to look with my own eyes. It was as strange as seeing a house-brick suddenly emit light,” Monat said.

GreenLight.jpgThe effect was real, however. Their infrared laser was being converted to green light – light of higher energy – in a process known as third- harmonic generation.

“One could imagine that a small green light indicator could help users of numerous Internet applications. This could be used to immediately inform companies such as Skype of a problem in the clarity of their connections, thereby allowing them to fix this in real time, all without the end user even noticing,” Monat said of the discovery’s potential.

The key to this unlikely event was a regular pattern of submicroscopic airholes in the researchers’ silicon chip, creating what is known as a photonic crystal. At the time of the discovery, Monat and Grillet were assisting doctoral student Bill Corcoran with experiments on slow light, itself a very novel and surprising phenomenon.

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“The experiments use specially designed photonic crystals from our colleagues at St. Andrews in Scotland. They allow us to slow the laser light used for telecommunications to one-fortieth of its usual speed,” Corcoran said. “As the light slows down, the energy from the laser is greatly concentrated. This energy can be used like traffic lights on the road to control the movement of large amounts of optical data through networks much more efficiently.”

The researchers said that converting infrared to green light adds another important tool to the impressive suite of capabilities of silicon, already the material of choice for the microelectronics industry.

“Being able to control light on a chip, along wires no wider than one-hundredth of the width of a human hair, represents the first step to realize all sorts of operations with significantly better performance than electronics alone,” Monat said. “And if we can do that in silicon, even more complex and exciting architectures become possible by integrating and marrying both the photonic and electronic worlds.”

The research team’s paper, “Green Light Emission in Silicon Through Slow-Light Enhanced Third-Harmonic Generation in Slow Light Photonic-Crystal Waveguides,” was published online in Nature Photonics on March 22.

For more information, visit: www.usyd.edu.au

Published: March 2009
Glossary
chip
1. A localized fracture at the end of a cleaved optical fiber or on a glass surface. 2. An integrated circuit.
infrared
Infrared (IR) refers to the region of the electromagnetic spectrum with wavelengths longer than those of visible light, but shorter than those of microwaves. The infrared spectrum spans wavelengths roughly between 700 nanometers (nm) and 1 millimeter (mm). It is divided into three main subcategories: Near-infrared (NIR): Wavelengths from approximately 700 nm to 1.4 micrometers (µm). Near-infrared light is often used in telecommunications, as well as in various imaging and sensing...
nano
An SI prefix meaning one billionth (10-9). Nano can also be used to indicate the study of atoms, molecules and other structures and particles on the nanometer scale. Nano-optics (also referred to as nanophotonics), for example, is the study of how light and light-matter interactions behave on the nanometer scale. See nanophotonics.
photonic crystals
Photonic crystals are artificial structures or materials designed to manipulate and control the flow of light in a manner analogous to how semiconductors control the flow of electrons. Photonic crystals are often engineered to have periodic variations in their refractive index, leading to bandgaps that prevent certain wavelengths of light from propagating through the material. These bandgaps are similar in principle to electronic bandgaps in semiconductors. Here are some key points about...
photonics
The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems. The range of applications of photonics extends from energy generation to detection to communications and...
waveguide
A waveguide is a physical structure or device that is designed to confine and guide electromagnetic waves, such as radio waves, microwaves, or light waves. It is commonly used in communication systems, radar systems, and other applications where the controlled transmission of electromagnetic waves is crucial. The basic function of a waveguide is to provide a path for the propagation of electromagnetic waves while minimizing the loss of energy. Waveguides come in various shapes and sizes, and...
chipCommunicationsCUDOSelectronicfiber opticsgreenGrilletinfraredInternetmicroelectronicsMonatnanoNews & Featuresphotonicphotonic crystalsphotonicsResearch & TechnologysiliconSkypeslow lightSt. Andrewsthird-harmonic generationUniversity of SydneyWaveguide

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