Speckle-Based Relative Wavelength Measurements – A Cost-Effective Alternative

Highly accurate relative wavelength changes can be determined from speckle shifts using a simple setup that illuminates a rough surface and records the speckle pattern at a high angle. The standard deviation of the measured wavelength residuals compared to a commercial Fizeau-type wavemeter was reduced by introducing a multi-ROI evaluation scheme from 65 fm to 35 fm over a tuning range of 0.3 nm. The speckle-shift-based wavelength sensor could therefore replace conventional wavemeters in certain use cases.