Principles and realization of a novel instrument for high performance displacement measurement-nanometer laser ruler

This paper introduces a novel instrument for displacement measurement-a nanometer laser ruler, in which some special concepts of laser physics are utilized, such as orthogonal polarization of laser modes, mode competition, power tuning and the law that changes of λ/2 in cavity length means the variation of one longitudinal mode spacing in frequency. Besides having a simple structure, the ruler has high resolution (79 nm), large measuring range (12 mm), and excellent linearity (5×10−5). The laser is the ruler itself. It can be applied to various fields. The way to implement the ruler is also introduced. In the end, some errors of the ruler are discussed.