Frequency stabiliztion of Helium-Neon lasers for length metrology

In this book, a simple and inexpensive method to stabilize the frequency of Helium-Neon lasers is described. The method is based on two orthogonally polarized modes emitted from the laser. The book demonstrates frequency stability measurement results of the stabilized laser against a reference laser. The laser reached a relative stability of 1 x 10-9, which is enough for length metrological applications.