Laser frequency offset-locking using electromagnetically induced transparency spectroscopy of <sup>85</sup>Rb in magnetic field

Laser frequency offset-locking using electromagnetically induced transparency spectroscopy of ⁸⁵Rb in magnetic field

Wang Han-Mu^{1, 2}, Cheng Hong^{1, 2}, Zhang Shan-Shan^{1, 2}, Xin Pei-Pei^{1, 2}, Xu Zi-Shan^{1, 2}, Liu Hong-Ping^{1, 2, †}

(color online) Monitored frequency deviation of the probe laser with and without locking. The red line corresponds to frequency offset-locking using the EIT signal under zero magnetic field while the blue one corresponds to frequency offset-locking using the EIT signal with transition 1 in the magnetic field of 8 G. Compared to the free-running denoted by the black line, the laser frequency deviation is strongly suppressed after locking on. The frequency deviation is less than 1 MHz in a given period of 500 s, resulting in a linewidth estimation of less than 0.5 MHz for each single laser.