Theoretical And Experimental Investigation Of Dual-frequency Laser Based On Faraday Effect And Zeeman Effect

Laser heterodyne interferometer has advantages of high measuring precision and anti-environment disturbance ability. It has been broadly applied in mechanical industry. The dual-frequency laser as a light source takes a key element in the interferometer. A new dual-frequency laser of mid-frequency difference, i.e. magnetic rotation-Zeeman dual-frequency laser, has been proposed in this paper. The principle of the laser is as follows: the spectrum of Ne atom is split in the longitudinal magnetic field. The left-handed circularly polarized and right-hand circularly polarized are brought with different frequency. Magneto-optical material is placed in the magnetism screened room which is in the laser resonant cavity. According to the Faraday Effect, when the light which is in the resonant cavity pass the magneto-optical material, the refraction difference between left-handed circularly polarized light and right-handed circularly polarized light leads to the different length of resonant cavity. According to the laser resonant cavity theory, the different length of resonant cavity leads to different frequency. Then the laser will output beams with △v different frequency. The optical property of magnetophotonic crystals is studied in order to enhance the integration rate of the laser system. The main contents are:(1) Applied laser resonant cavity theory and the electromagnetic wave theory of Faraday Effect, the relational formula of frequency difference of the laser, magnetic induction intensity and length of resonant cavity is obtained. From the formula, the result that the frequency difference directs with the cavity length and inverse with the magnetic induction intensity is acquired.(2) Optical property of the Zeeman part is investigated experimentally. When the magnetic induction intensity is bigger than 3mT, the frequency difference of the laser will become stabilization and it is directly proportional to the magnetic induction intensity and inversely proportional to the peak-peak value of the beat frequency. The number of the longitudinal mode is increasing with the enhancement of the magnetic induction intensity.(3) The Verdet constants and magneto-optical figure of merit of magneto-optical materials (BGO, Tb20 glass and Tb25 glass) at 632.8nm are measured by employing the double frequency method. And the results demonstrate that the magneto-optical property of Tb20 is better than BGO. Design the structure of magnetism screened room by using MagNet. Based on the structure, the room is produced, and the leak of magnetic induction intensity is below 1%. The magnetism screened room basically reaches the design requirements.(4) Several kinds of structure of one-dimensional magnetophotonic crystals are analyzed using equation of state. By choosing proper structure, the Faraday rotation can be increased by several thousand times, and the transmissibility is also increased in the center wavelength.