Laser Light Pulsed on Silicon

The first mode-locked silicon evanescent laser has been constructed, a significant step toward combining lasers and other key optical components with silicon electronics to create new types of integrated circuits.

The University of California, Santa Barbara (UCSB) research provides a practical way to integrate optical and electronic functions on a single chip for integrated circuits that are less expensive, lower power and more compact. It will be reported in the Sept. 3 issue of Optics Express and is available now online.

A research team at the University of California, Santa Barbara have developed the first mode-locked silicon evanescent laser, a step toward combining lasers and optical components in silicon to create new types of integrated circuits. (Image: Peter Allen, UCSB)

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? It is extremely difficult, nearly impossible, to create a laser in silicon.

The 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. (See: "Hybrid Silicon Laser Chip That Emits, Guides Light Developed"). In that work, John Bowers, a professor of electrical and computer engineering, and his team created laser light from electrical current on silicon by placing a layer of InP (indium phosphide) above the silicon.

In this new study, Bowers, doctoral student Brian Koch and others used the same 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. Using existing silicon technology would potentially be less expensive and a more feasible way to mass produce future-generation devices that would use both electrons and photons to process information, rather than the traditional way of just electrons

The work was supported by funds from the Microsystems Technology Office of DARPA.

The research paper can be viewed at: www.opticsexpress.org/abstract.cfm?id=140973