| 摘要 |
PROBLEM TO BE SOLVED: To obtain a maximum output strength by a single wavelength by performing the fine control of the resonator length of an HeNe laser having a resonator length capable of making the number of longitudinal mode spectra four, so as to make the number of the longitudinal mode spectra three. SOLUTION: By passing through a polarizer 2, light emitted from a laser having an internal resonator is strength-modulated by the beat frequency between longitudinal modes. This modulated light is detected by a detector 3 and is amplified by an amplifier 10. And it is mixed by a mixer 12 with the output of an oscillator 11 of a frequency near to the beat frequency between longitudinal modes or its double frequency. The output (difference frequency) of the mixer 12 is rectification-detected, and the envelope of a signal is taken out. The frequency of the envelope is connected into a voltage by a frequency- voltage converter 13, and the resonator length of the laser is controlled by a power amplifier 15 and a heater 16 so as to make the frequency of the envelope constant. |
