All-silicon laser shines out

Scientists at Intel claim to have made the first all-silicon laser. This could lead to the development of silicon chips that can be used in both electronic and photonic applications.

Existing photonic devices are made from expensive compound semiconductor materials such as gallium arsenide or indium phosphide.

Silicon dominates the microelectronics industry but it is not used in photonic applications because it does not emit light efficiently.

Last year, researchers at the University of California discovered a way to exploit the Raman effect and achieve laser action in silicon, although their device needed an 8 m-long optical fibre to work.

The Raman effect, which uses vibrations in a material to create optical gain, is routinely used in the telecommunications industry to amplify optical signals.

Now, Haisheng Rong and colleagues at Intel laboratories in Santa Clara, California and Jerusalem in Israel have made a compact all-silicon Raman laser on a single silicon chip.

Rong and co-workers started by making an S-shaped silicon waveguide with standard photolithography and etching techniques. The waveguide had an effective core area of about 1.6 square microns and was around 4.8 cm long.

Next, they fabricated the Raman laser optical cavity by coating one of the waveguide facets with a highly reflecting material.

The team then pumped the cavity with pulses from a laser operating at a wavelength of 1536 nm. The optical cavity began to lase at a wavelength of 1669.6 nm when the pump power reached 0.4 µW.

At present, the device can only operate for about 100 nanoseconds before a process called two-photon absorption stops the laser action.