Optical frequency shifter for heterodyne measurement

摘要

In an optical frequency shifter for producing an output light beam 35' which has orthogonal p- and s- components having optical frequencies different from each other, a laser oscillator 11' generates a laser beam 12' including the p- and the s-components which have the same optical frequency and which are separated by a polarizing beam splitter 41 as first and second partial beams 42,43 respectively. The first and the second partial beams are acoustooptically shifted 17' in frequency relative to each other to produce first and second intermediate beams, with the p- and s-components kept unchanged. The first and second intermediate beams are combined by an additional beam splitter 52 into the output light beam. Specifically, only either one of the first and second intermediate beams may be subjected to the acoustooptic frequency shift, with the frequency of the other intermediate beam kept unchanged (as shown). Alternatively, both the first and second intermediate beams may be subjected to acoustooptic frequency shift. The arrangement forms a source of object and reference waves in a heterodyne system for measuring e.g. length. IMAGE