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Topic Name: The world's first mode-locked silicon evanescent laser

Category: Photonics

Research persons: John Bowers

Location: Electrical & Computer Engineering,University of California,Santa Barbara, CA 93106-9560, United States

Details

Researchers at UC Santa Barbara have announced they have built the world's first mode-locked silicon evanescent laser, a significant step toward combining lasers and other key optical components with the existing electronic capabilities in silicon. The research provides a way to integrate optical and electronic functions on a single chip and enables new types of integrated circuits. It introduces a more practical technology with lower cost, lower power consumption and more compact devices. The research will be reported in the September 3 issue of Optics Express and is published online today.

Mode-locked evanescent lasers can deliver stable short pulses of laser light that are useful for many potential optical applications, including high-speed data transmission, multiple wavelength generation, remote sensing (LIDAR) and highly accurate optical clocks.

Computer technology now depends mainly on silicon electronics for data transmission. By causing silicon to emit light and exhibit other potentially useful optical properties, integration of photonic devices on silicon becomes possible. The problem in the past? It is extremely difficult, nearly impossible, to create a laser in silicon.

Less than one year ago, a research team at UCSB and Intel, led by John Bowers, a professor of electrical and computer engineering, created laser light from electrical current on silicon by placing a layer of InP above the silicon. In this new study, Bowers, Brian Koch, a doctoral student, and others have used this platform to demonstrate electrically-pumped lasers emitting 40 billion pulses of light per second. This is the first ever achievement of such a rate in silicon and one that matches the rates produced by other mediums in standard use today. These short pulses are composed of many evenly spaced colors of laser light, which could be separated and each used to transmit different high-speed information, replacing the need for hundreds of lasers with just one.

Creating optical components in silicon will lead to optoelectronic devices that can increase the amount and speed of data transmission in computer chips while using existing silicon technology. Employing existing silicon technology would represent a potentially less expensive and more feasible way to mass-produce future-generation devices that would use both electrons and photons to process information, rather than just electrons as has been the case in the past.

About Researcher:

John Bowers
Professor
Electrical & Computer Engineering
Contact Information
Phone: (805) 893-8447
E-Mail: bowers@ece.ucsb.edu
Office: Engineering I, Room 4163
Address
Electrical & Computer Engineering
University of California
Santa Barbara, CA 93106-9560
Bowers has worked with Indium Phosphide-based materials and lasers for more than 25 years. Currently his research is focused on developing novel optoelectronic devices with data rates as high as 160Gb/s and techniques to bond dissimilar materials together to create new devices with improved performance.

Funded:

This research builds upon the development of the first hybrid silicon laser, announced by UCSB and Intel a year ago, enabling new applications for silicon-based optics. The research was supported by funds from the Microsystems Technology Office of DARPA.

Previous Research with Intel-

Intel, UC Santa Barbara Develop World's First Hybrid Silicon Laser

The researchers were able to combine the light-emitting properties of Indium Phosphide with the light-routing capabilities of silicon into a single hybrid chip. When voltage is applied, light generated in the Indium Phosphide enters the silicon waveguide to create a continuous laser beam that can be used to drive other silicon photonic devices. A laser based on silicon could drive wider use of photonics in computers because the cost can be greatly reduced by using high-volume silicon manufacturing techniques.

“This could bring low-cost, terabit-level optical ‘data pipes’ inside future computers and help make possible a new era of high-performance computing applications," said Mario Paniccia, director of Intel’s Photonics Technology Lab. "While still far from becoming a commercial product, we believe dozens, maybe even hundreds of hybrid silicon lasers could be integrated with other silicon photonic components onto a single silicon chip.”

"Our research program with Intel highlights how industry and academia can work together to advance the state of science and technology," said John Bowers, a professor of electrical and computer engineering at UC Santa Barbara. “By combining UCSB’s expertise with Indium Phosphide and Intel’s silicon photonics expertise, we have demonstrated a novel laser structure based on a bonding method that can be used at the wafer-, partial-wafer or die-level, and could be a solution for large-scale optical integration onto a silicon platform. This marks the beginning of highly integrated silicon photonic chips that can be mass produced at low cost.”

Technical Details

While widely used to mass produce affordable digital electronics today, silicon can also be used to route, detect, modulate and even amplify light, but not to effectively generate light. In contrast, Indium Phosphide-based lasers are commonly used today in telecommunications equipment. But the need to individually assemble and align them has made them too expensive to build in the high volumes and at the low costs needed by the PC industry.

The hybrid silicon laser involves a novel design employing Indium Phosphide-based material for light generation and amplification while using the silicon waveguide to contain and control the laser. The key to manufacturing the device is the use of a low-temperature, oxygen plasma -- an electrically charged oxygen gas -- to create a thin oxide layer (roughly 25 atoms thick) on the surfaces of both materials.

When heated and pressed together the oxide layer functions as a “glass-glue” fusing the two materials into a single chip. When voltage is applied, light generated in the Indium Phosphide-based material passes through the oxide “glass-glue” layer and into the silicon chip’s waveguide, where it is contained and controlled, creating a hybrid silicon laser. The design of the waveguide is critical to determining the performance and specific wavelength of the hybrid silicon laser.

Today’s announcement builds on Intel’s other accomplishments in its long-term research program to “siliconize” photonics using standard silicon manufacturing processes. In 2004, Intel researchers were the first to demonstrate a silicon-based optical modulator with a bandwidth in excess of 1GHz, nearly 50 times faster than previous demonstrations of modulation in silicon. In 2005, Intel researchers were the first to demonstrate that silicon could be used to amplify light using an external light source to produce a continuous wave laser-on-a-chip based on the “Raman effect.”