Long-term drift laser frequency stabilization using purely optical reference

We describe an apparatus for the stabilization of laser frequencies that prevents long-term frequency drifts. A Fabry - Perot interferometer is thermostated by referencing it to a stabilized He - Ne laser (master), and its length is scanned over more than one free spectral range allowing the analysis of one or more lines generated by other (slave) lasers. A digital acquisition system makes the detection of the position of all the laser peaks possible, thus producing both feedback for the thermostat and the error signal used for stabilizing the slave lasers. This technique also allows for easy, referenced scanning of the slave laser frequencies over range of several hundred MHz, with a precision of the order of a few MHz. This kind of stabilization system is particularly useful when no atomic or molecular reference lines are available, as in the case of rare or short lived radioactive species.