Active control of grating interferometers for extended-range low-noise operation.

An active control method is proposed and demonstrated to improve grating-based laser interferometry to achieve low-noise (subpicometer resolution) and multiwavelength unambiguous range of operation simultaneously. The method modifies a recurrent calibration-based path stabilization algorithm to extract high-resolution and low-resolution data in parallel. This extended range recurrent calibration method is experimentally verified by implementing it on the micromachined scanning grating interferometer (microSGI).