| 摘要 |
PURPOSE:To subject radiating beams to FM modulation by a method wherein an electric signal obtained through heterodyne detection of a laser beam path and laser beams is applied further to the piezoelectric element of a laser resonator through a discriminator after the heterodyne detection to stabilize oscillation and to modulate an oscillator for the second heterodyne detection. CONSTITUTION:A part of the beam of a CO2 laser L is led out, mixed with the beam from a laser O1 for local oscillation and subjected to heterodyne detection M1, and intermediate-wave voltage VF1 thus obtained is inputted in a discriminator D'. The output of a local oscillator O2 is subjected to frequency modulation M0, to mixture M2 and to heterodyne detection, and higher-frequency voltage VF2 thus obtained is subjected to the frequency-voltage conversion of the central frequency (f) thereof through a BPF. The output thus obtained is applied to the piezoelectric element P built in the laser through DC amplifiers A1 and A2 whose gains are G1 and G2 respectively, whereby the frequency is adjusted. Since one feedback loop is formed in this way, the fluctuation of the frequency of the laser L is fed back immediately to the element P to control the interval between mirrors M and M' and also to control the frequency. Moreover, by double superheterodyne detection, the linearity of the frequency characteristic of a discriminator D is maintained very excellently. |
