METHOD FOR STABILIZING FREQUENCY OF INTERNAL MIRROR TYPE HE-NE LASER HAVING 543-NM OSCILLATING WAVELENGTH

摘要

PURPOSE:To stabilize the frequency of the title laser within a wide range by impressing a specific static magnetic field upon the inside of the laser thin tube and, at the same time, feedback controlling the resonator length by utilizing the intensity difference or intensity ratio between adjacent longitudinal modes as an error signal after detecting the difference or ratio. CONSTITUTION:The 543-nm He-Ne laser light oscillated from a laser tube LA is separated into light components respectively having inherent polarizing directions C1 and C2 at a polarization beam splitter PBS and the components are respectively detected and amplified by means of PIN photodiodes PD1 and PD2 and amplifiers AM1 and AM2 as DCs. Outputs of the amplifiers AM1 and AM2 are inputted to a differential amplifier DA where an intensity difference between the light components is detected. The intensity difference is outputted from the amplifier DA as an error signal after amplification and the collector current of a transistor Tr2 is controlled from the amplified error signal. Then the electric power supplied to a heater HE is controlled by the controlled collector current and the resonator length of the laser tube LA is corrected. Therefore, the longitudinal mode can be stabilized to a fixed frequency position.