Application of double metal/dielectric gratings in optical displacement detection

A high-resolution displacement detection based on in-plane and out-of-plane moving gratings is discussed in this paper. To improve the detective resolution and stability, a model of a double metal/dielectric optical grating is established to investigate the tolerance of grating parameters. The zero-order optical diffraction efficiency of the grating is calculated by rigorous coupled-wavelength analysis, which depends on the grating parameters. The dependency relation curves are a cosine and pulse curve, respectively, for in-plane movement with the highest slope superior to 0.29%/nm and the highest resolution can reach to 0.01 nm, and for out-of-plane movement with the highest slope superior to 1.63%/nm and the optimum resolution can reach to 0.002 nm. These results indicate that the in-plane effect is feasible for a long-range and high-resolution displacement detection, and the out-of-plane effect is suitable for small-range and high-resolution displacement detection. Both kinds of effects provide a designed solution for the development of a high-resolution displacement sensor.