In what is being reported as a scientific breakthrough and a world first, scientists at Intel Corp., Santa Clara CA, have used standard silicon manufacturing processes to create continuous-wave silicon lasers.

Intel says the technology could help bring low-cost, high-quality lasers and optical devices to mainstream use in computing, communications and medical applications.

As recently reported in the prestigious journal Nature, the giant chip maker's researchers have found a way to use the Raman effect and silicon's crystalline structure to amplify light as it passes through. When combined with light from an external source, the experimental device produces a continuous, high-quality laser beam.

While still far from becoming a commercial product, Intel says the ability to build a laser from standard silicon could lead to inexpensive optical devices that move data inside and between computers at the speed of light, ushering in a flood of new applications for high-speed computing.

"Fundamentally, we have demonstrated for the first time that standard silicon can be used to build devices that amplify light," Dr. Mario Paniccia, Intel director, Photonics Technology Lab, says. "The use of high-quality photonic devices has been limited because they are expensive to manufacture, assemble and package. This research is a major step toward bringing the benefits of low-cost, high-bandwidth silicon based optical devices to the mass market."

Building a Raman laser in silicon begins with etching a waveguide as a conduit for light on a chip. Silicon is transparent to infrared, so that when light is directed into a waveguide it can be contained and channeled across a chip.

Like with the first laser developed in 1960, Intel researchers use an external light source to pump light into their chip. As light is pumped in, the natural atomic vibrations in silicon amplify the light as it passes through the chip. This amplification, the Raman effect, is more than 10,000 times stronger in silicon than in glass fibers.

Raman lasers and amplifiers are used today in the telecom industry and rely on miles of fiber to amplify light. By using silicon, Intel says its researchers were able to achieve gain and lasing in a silicon chip just a few centimeters in size.

By coating the sides of the chip with a reflective thin-film material, similar to coatings used on high-quality sunglasses, the team is able to contain and amplify the light as it bounces back in forth inside the chip. As they increase the pump energy, a critical threshold point is reached where, instantaneously, a very precise beam of coherent laser light exits the chip.

Initially, the workers discovered that increasing the light pump power beyond a certain point no longer increased amplification and eventually even decreased it. The reason was a physical process called two-photon absorption, which occurs when two photons from the pump beam hit an atom at the same time and knock an electron away. These excess electrons build up over time and collect in the waveguide until they absorb so much light that amplification stops.

Intel says its breakthrough solution to this problem was to integrate a semiconductor structure, technically called a PIN (P-type - intrinsic - N-type) device into the waveguide. When a voltage is applied to the PIN, it acts like a vacuum and removes most of the excess electrons from the light's path. The PIN device combined with the Raman effect produces a continuous laser beam.

The silicon photonics research team has achieved a number of breakthroughs, starting in 2004 with the first silicon-based optical modulator to encode data at 1GHz, an increase of over 50 times the previous research record of about 20MHz.