Manipulating nanowires for single-mode lasers

A single-nanowire laser has been developed that, unlike earlier ones, which operated mostly in multiple modes, operates in a controllable single mode.

Researchers from Zhejiang and Peking universities used a nanowire between 50 and 75 μm in length and 200 nm in diameter to develop the breakthrough laser, which emits a wavelength of about 738 nm.

To produce a nanowire that functions as a single-mode laser, the scientists excited a looped nanowire with a pulsed laser. The looped nanowire doubles as a loop mirror, reducing the lasing threshold and increasing the wire’s reflectivity. Together, the low threshold and high reflectivity create a high-quality lasing cavity in the nanowire.

By adjusting the loop size with fiber probes, the team tuned the laser’s wavelength. When the loop size was reduced, the optical path of the smaller lasing cavity caused the wavelength to change.

This single-mode laser could be used as a nanoscale coherent light source for optical communications, sensing and signal processing applications.

A study of their findings was published online Feb. 15, 2011, in Nano Letters (doi: 10.1021/nl1040308).