Periodic optical Faraday-effect chopper
Abstract
A Faraday effect optical chopper is described which controls radiation at the 1.06 micron wavelength in the periodic mode with repetition rates up to 100 Hz. The chopper includes a Faraday rotation, an air-core solenoid which produces a magnetic induction of 0.5-1 T for 45 deg. rotation of the polarization plane, and a 3.6 nF capacitor bank which discharges into the solenoid in pulses. The capacitor bank is energized from a 220/800 V - 50 Hz transformer through a diode-rectifier bridge. The rotation angle is proportional to the square root of the capacitor discharge energy and inversely proportional to the square root of the solenoid radius, but does not depend on the number of solenoid turns, with a constant coefficient equal to the magnetic permeability of the medium multiplied by the Verdet constant and with a variable coefficient which depends on the ratio of solenoid radius to solenoid length and the ratio of rotator rod length to solenoid length. The normalized rotation angle increases from zero to unity as the relative length of the rotator rod increases, reaching unity at a smaller relative rod length as the relative solenoid radius decreases. The relative radial nonuniformity of the rotation angle, referred to the rotation angle at the solenoid axis, also depends on those two ratios: increasing monotonically as the relative solonoid radius increases but increasing with a sharp peak and then decreasing to zero as the relative rotator rod length increases beyond the solenoid length.
- Publication:
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USSR Rept Eng Equipment JPRS UEQ
- Pub Date:
- March 1986
- Bibcode:
- 1986RpEE........58G
- Keywords:
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- Electro-Optics;
- Faraday Effect;
- Optical Switching;
- Solenoids;
- Capacitors;
- Polarization (Waves);
- Energy Production and Conversion