Graham D. Bruce, Laura O’Donnell, Mingzhou Chen, and Kishan Dholakia
Optics Letters 44(6), 1367-1370 (2019)
The measurement of the wavelength of light using speckle is a promising tool for the realization of compact and precise wavemeters and spectrometers. However, the resolution of these devices is limited by strong correlations between the speckle patterns produced by closely-spaced wavelengths. Here, we show how principal component analysis of speckle images provides a route to overcome this limit. Using this, we demonstrate a compact wavemeter which measures attometer-scale wavelength changes of a stabilized diode laser, eight orders of magnitude below the speckle correlation limit.