Intel researchers move silicon photonics into the mid-infrared

February 25, 2008, Santa Clara, CA--The feasibility of extending the wavelength of operation of silicon lasers from the near- to the mid-infrared has been given a boost, in a paper published online this week in Nature Photonics. Intel has demonstrated the world's first cascaded Raman silicon laser, extending the operating wavelength out to 1848 nm, with even longer wavelengths possible.

Demonstration of a cascaded silicon Raman laser establishes a pathway to extending the laser wavelength into the mid-IR region for gas sensing and other important spectroscopy applications that are possible today only with complicated, bulky, expensive, or cryogenically cooled lasers.

Cheap and powerful semiconductor lasers that operate in the mid-infrared (2 microns to 5 microns) region are highly sought for applications such as medical diagnostics and environmental monitoring, but do not exist at present.
Haisheng Rong and colleagues at Intel have demonstrated that silicon-chip-based lasers that exploit cascaded Raman lasing may provide the answer. Although silicon Raman lasers have been made before, their wavelength of operation has always been limited to around 1.6 microns.

The Intel team has successfully demonstrated that, by exploiting the Raman effect not once but twice within a silicon waveguide, it is possible to create a silicon-chip laser that emits milliwatt-scale powers at a wavelength of 1.848 microns. This is the longest wavelength reported so far for silicon Raman lasers and is tantalizingly close to the mid-infrared window. The research offers hope that by optimizing the design it should be possible to make lasers that operate at even longer wavelengths. It could also lead to silicon-based lasers that offer compactness and lower cost compared to current lasers used in a wide range of spectroscopy, sensing and medical applications.