| 摘要 |
PURPOSE:To reduce the noise level of a second-harmonic laser beam in a low-fre quency region by a method wherein the high-frequency component of a laser beam which has been passed through a resonator block is detected, it is fed back to an excitation light source and the noise of the second-harmonic laser beam generated by the resonator block is reduced. CONSTITUTION:A noise signal obtained from the high-frequency component of one part of a second-harmonic laser beam generated by a resonator block 11 is negatively fed back by a negative-feedback loop system 35, it is added to an LD constant-current drive circuit 31 in a constant-current drive system 34 at a timing at which a temperature control system 27 is operated, and a laser diode 12 is driven. Since an excitation laser beam generated by the laser diode 12 for excitation use and a second-harmonic laser beam generated by the resonator block 11 are correlated electrically and optically, the generation of the second-harmonic laser beam can be controlled by controlling the driving current of the laser diode 12. Consequently, the noise level on the low-frequency side of the second-harmonic laser beam can be reduced. |
