Consumer-webcam-based laser wavemeter has subpicometer accuracy and picowatt sensitivity

Melbourne, Australia and Huntingdon, PA--A compact laser wavemeter developed by Robert Scholten of the ARC Centre of Excellence for Coherent X-ray Science, School of Physics, University of Melbourne and James White of Juniata College is based on a diffraction grating and a consumer-grade webcam. The instrument has an absolute accuracy of 0.7 pm -- fine enough to resolve individual hyperfine transitions of the rubidium absorption spectrum -- and requires only 1 pW of laser power for measurement.

"The accessibility, simplicity, and cost make it feasible to provide such precision measurements for every single laser in a laboratory," says Scholten. The instrument is simple enough to be constructed in undergraduate physics labs – "and could easily be a high-school project," adds Scholten. "It would provide excellent training in optics and the wave nature of light, and once constructed, the device can be used to elucidate the quantum-mechanical structure of matter, for example by measuring the fine-structure splitting or even the hyperfine structure of atoms such as sodium."

The wavemeter is described in the AIP's journal Review of Scientific Instruments. As noted in the paper, the webcam-based wavemeter clearly resolves the spectrum of a multimode laser, which a conventional interferometric wavemeter doesn't do. As a result, the new instrument can be used to characterize external cavity diode lasers and to monitor lasers used in atom cooling and trapping experiments.

Source: http://www.eurekalert.org/pub_releases/2012-12/aiop-woa120312.php