METHOD FOR STABILIZING FREQUENCY OF INTERNAL MIRROR TYPE HE-NE LASER HAVING 534-NM OSCILLATING WAVELENGTH

摘要

PURPOSE:To stabilize the frequency of the title laser within a wide range by preventing inversion of polarization by impressing a specific static magnetic field upon the inside of the laser thin tube and, at the same time, by feedback-controlling the resonator length by utilizing the phase of the waveform of a recessed part produced at the center of the output waveform of the light component in an inherent polarizing direction having a high intensity as an error signal after detecting the phase at the time of three-longitudinal oscillating time when the light component is positioned in a specific state. CONSTITUTION:The resonator length of a laser tube LA is modulated by modulating the electric power supplied to a heater HE wound around the laser tube LA with signals from an audio frequency oscillator AFOSC. Then the differential signal of the recessed section waveform of the area A shown in the upper graph of the figure is obtained by phase-sensibly detecting the frequency component from the output light of the laser passing through a linearly polarizing plate LP1 place in the direction of the inherent polarizing direction C2 of the component by means of a lock-in amplifier LIA. The resonator length can be kept constant when the length is controlled by means of the heater HE by utilizing the linear slope section at the central part of the differentiating signal as an error signal. Therefore, the frequency of the laser can be stabilized.