Nanoscanning method for high-density grating measurement

The high-density grating is routinely used in a wide variety of applications using optics. However usually it is hard to measure such gratings directly by using conventional methods such as stylus profilometer and scanning probe microscope (SPM) that might damage the grating due to its fragile surface. A novel nano-scanning method based on the Talbot effect for measurement of a high-density grating is described in this paper. This method takes the advantage of the Talbot self-imaging effect of a grating with the conventional scanning near-field optical microscopy (SNOM) technique for measurement of a high density grating in nanometer accuracy without causing any damage to the grating under test. The noteworthy advantages of this method are its simple structure, easy operation and fast measurement of the quality of the grating under test. Three different kinds of gratings are measured in our experiments and the result demonstrates that this method is effective for evaluation of a high-density grating approximatively.