Method and apparatus for determining the wave number of optical spectrum radiation

摘要

Method and apparatus for determining the wave number of optical spectrum radiation, particularly for use in controlling lasers. Two parts of a beam provided by a source to be monitored, particularly a laser, are directed to two double-wave interferometers. The differences of the optical path lengths delta of the interferometers are assigned a difference of lambda /4 which corresponds to a phase difference of pi /2. The two optical output signals emerging from the interferometers are converted into sinusoidal electrical waves in quadrature as a function of the wave number sigma = 1/ lambda of the laser and the period 1/ delta of the two sinusoidal electrical waves. The electrical waves are processed in suitable circuitry to obtain a modulo value 1/ delta of the wave number. These steps are repeated for different values of delta so as to progressively eliminate uncertainty in the value of the wave number.