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FADOF and Technique of frequency stabilization
The current position:Research < FADOF and Technique of frequency stabilization
1.Atomic Faraday anomalous dispersion optical filter

      Atomic Faraday Anomalous Dispersion Optical Filter (Faraday Anomalous Dispersion Optical Filter, FADOF) by the longitudinal magnetic field in the atomic vapor bubble and placed on both ends of the polarization direction of polarizing prism orthogonal to each other. Linear polarized light can be seen as a left-hand circularly polarized light and right-handed circularly polarized light of linear superposition, the magnetic field, the atomic energy level will retreat degenerate, Zeeman split. Because of left-handed and right-handed polarized light in a magnetic field under the influence of refractive index is different, leading to them in and atomic interaction, transmission speed is different, so, two circularly polarized components, relative phase shift will occur leading to final superposition and linear polarization surface have certain rotation. Atomic vapor Faraday effect by the resonance is that near the resonance absorption line of the signal light polarization direction of rotation, only rotated 90 ° and the odd times of the signal light by partial detector, and rotate the polarization direction of the light does not take place outside the band, was held up by the partial detector.

       At present, the research group has successfully implemented 87 Rb atoms of 780 nm, 1529 nm FADOF [1, 2], Cs atom 455 nm FADOF [3], the Sr atom FADOF 461 nm, 423 nm Ca atoms FADOF, covered from purple light to the  communication wavelengths.

2.FADOF laser frequency stabilization.

        Faraday atomic optical filter function is extracted from the strong background of broadband light faint narrow-band laser signal, namely through the FADOF as frequency selective element, narrow-band laser signal feedback to the semiconductor laser, the semiconductor laser output frequency stability in the atomic resonance transition spectral line. Normally, the narrower the line width of atomic optical filter, the more conducive to the laser frequency stability.

       The longer the external cavity, the smaller the line width. So we consider increasing the cavity length to narrow linewidth, if otherwise increase the cavity length, namely increases loss, also can give light path increase difficulty collimation. So we consider using optical fiber as external cavity to increase the cavity length, narrow linewidth, both increased the cavity length, and not to give the light path collimating increase the difficulty. So that the laser output frequency thermal noise on the surrounding environment, such as mechanical vibration noise is not sensitive. The longer the cavity length, the smaller the longitudinal mode interval, line width will be smaller, atoms within the transmission bandwidth filters will have more models, the competition between them, will have more quality pattern to stand out, and the frequency of the laser will be more accurate, more stable.


                                   


Reference:

[1]Qinqing Sun,Wei Zhuang,Zhiwen Liu,and Jingbiao Chen,Electrodeless-discharge-vapor-lamp-based faraday anomalous-dispersion optical filter, Optics letters, (2011) Vol.36 No.23:4611-4613

[2]Qinqing Sun, Yelong Hong, Wei Zhuang, Zhiwen Liu, and Jingbiao Chen,Demonstration of an excited-state Faraday anomalous dispersion optical filter at 1529 nm by use of an electrodeless discharge rubidium vapor lamp,   Appl. Phys. Lett. 2012, vol.101, 211102,DOI: 10.1063/1.4767140.

[3]WANG Dong-Ying(王东颖), WANG Yan-Fei(王彦飞), TAO Zhi-Ming(陶智明), ZHANG Sheng-Nan(张盛楠) HONG Ye-Long(洪叶龙), ZHUANG Wei(庄伟), CHEN Jing-Biao(陈景标), Cs 455nm Nonlinear Spectroscopy with Ultra-narrow Linewidth,   Chin. Phys. Lett. Vol. 30, No. 6 (2013) 060601.
[4]Xinyu Miao, Longfei Yin, Wei Zhuang, Bin Luo, Anhong Dang, Jingbiao Chen, and Hong Guo,Demonstration of an external-cavity diode laser system immune to current and temperature fluctuations,Rev. Sci. Instrum., 82(8), 086106 (20110818).
[5]Tao Z, Hong Y, Luo B, et al.Diode laser operating on an atomic transition limited by an isotope ⁸⁷Rb Faraday filter at 780 nm.[J]. Optics Letters, 2015, 40(18):4348-51.