Major Advance Could Lead to New Innovations in Computing, Communications and Medical Applications
Intel announced a scientific breakthrough using standard silicon manufacturing processes to create the world's first continuous wave silicon laser.
As reported in today's issue of the journal Nature, Intel researchers have found a way to use the
so-called Raman effect and silicon's crystalline structure to amplify light as it passes through it.
When infused with light from an external source the experimental chip produces a continuous, high-quality
laser beam.
Technical Details
Building a Raman laser in silicon begins with etching a waveguide -- a conduit for light
on a chip. Silicon is transparent to infrared light so that when light is directed into a
waveguide it can be contained and channeled across a chip. Like the first laser developed
in 1960, Intel researchers used 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 researchers were able to achieve gain and lasing in a silicon chip just a few centimeters in size.
The Breakthrough
Initially, they discovered 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's breakthrough solution 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.
