AC Laser Interferometer

• The two frequencies Zeeman laser generates light of two different frequencies with opposite circular polarizations. The beams are splitted by the beam splitter B1. In this, one part travels towards B2 and from B2 to external cube corners, where the displacement is measured.

• Beams splitter B2 optically separates the frequencies f1 which is sent to a fixed reflector and then rejoins f1 at the beam splitter B2 to produce alternate light and dark interference. Now, the external cube corners moves which it will produce a change in f1 (i.e., ∆f1) in the returning beam frequency . So , the light beams move towards photo detectors p2 having frequencies f2 (i.e.,f1 to ∆ti ) and p2 will be changed into electric signal.

• The photo detector p1 receives signals from beam splitter B1 and changes the references beam f1 and f2 into electric signal . The two amplifiers A1 and A2 separate frequency difference signals f2 – f1 and f2 – (f1 + ∆f ) . The pulse converter extracts ∆f and displays in the form of pulses in analog or digital form in the output.

AC Laser Interferometer