| 摘要 |
PURPOSE:To obtain a laser with a stable intensity level by a method wherein a part of a laser output is extracted and a magnetic field applied to a Faraday element is feedback controlled corresponding to the intensity of the incident laser beam. CONSTITUTION:An input laser beam is linearly polarized with a polariscope P1 to be carried to a Faraday rotation device FR. A polarizing plane rotates according to an applying magnetic field intensity MF, and an output laser beam pases through a polariscope P2 and is reflected at a mirror RS, and Iout=kIincos<2>(theta-phi) is outputted, where theta=a tilt angle of axes of both polariscopes, phi=Faraday's rotating angle, and k=a constant. After extracing a part of the output, a photovoltage v is obtained by using a photoelectric material PM, and then is compared with a reference vo to get the deviation. The deviation is amplified at an amplifier A to drive a circuit PA. Current of an electromagnet is fedback controlled so taht a differential deviation DELTAvo becomes zero to keep a magnetic force MF constant. With this structure, a remarkably stable intensity level of laser can be obtained, and the angle theta can be arbitrarily set, so that a linearly polarized laser beam with high stability of polarization can be produced by setting a polarization plane at an arbitrary value. |
