铯原子激发态双色偏振光谱

Investigation of the two-color polarization spectroscopy between the excited states based on cesium atoms

基于铯原子阶梯型6S1/2-6P3/2-8S1/2 (852.3 nm+794.6 nm)能级系统,一束波长为852.3 nm的圆偏振光作为抽运光,将室温下气室中的铯原子由基态6S1/2激发到中间激发态6P3/2并极化,另一束波长为794.6 nm的线偏振光作为探测光,其频率在6P3/2—8S1/2态之间扫描,经过原子气室后差分探测便可获得铯原子激发态6P3/2—8S1/2能级跃迁之间的双色偏振光谱.实验上系统地测量、分析了抽运光频率失谐、偏振,以及抽运光与探测光同反向实验构型对双色偏振光谱的影响,并将其用于794.6 nm半导体激光器的稳频,锁频之后,225 s内的残余频率起伏约为0.5 MHz.

Two-color polarization spectroscopy(TCPS)of cesium 6 S1/2-6 P3/2-8 S1/2(852.3 nm+794.6 nm)ladder-type system in a room-temperature vapor cell are investigated.The frequency of 852.3 nm laser used as a pump beam is locked on one of the hyperfine transitions between the ground state 6 S1/2 and excited state 6 P3/2 by the saturated absorption spectroscopy technique,which can populate some atoms on the 6 P3/2 excited state and induce anisotropy in the atomic medium.The frequency of 794.6 nm laser serving as a probe beam is scanned across the whole 6 P3/2→8 S1/2 transition to ascertain this anisotropy,and thus the TCPS is obtained.In experiment,we measure and analyse the influence of frequency detuning of 852.3 nm pump laser on TCPS,and especially reveal that some of hyperfine energy levels of intermediate excited state 6 P3/2,which has no direct interaction with the 852.3 nm pump laser,are also populated by a small fraction of atoms with a specific speed in the direction of pump laser beam due to Doppler effect,so they also have contribution to the TCPS when the794.6 nm probe laser is scanned to the resonance transition line between the 6 P3/2 and 8 S1/2 states after the Doppler frequency shift has been considered.In addition,we prove that the atomic coherence like electromagnetically induced transparency effect obviously results in a narrower line width of TCPS in the case of counter-propagating experimental configuration than that in the case of pump beam co-propagating with the probe beam in the Cs vapor cell.Finally,we apply the TCPS with dispersive shaped feature to frequency stabilization with no modulation,and the frequency fluctuations of 794.6 nm laser are^0.5 MHz and^9.2 MHz for the frequency-locking and free running in^225 s,respectively.The above research work is expected to play a role in precisely measuring the atomic energy level structure and its related hyperfine structure constant(magnetic dipole and electric quadrupole coupling constants),and also in stabilizing the laser frequency to the excited state transition especially for the optical fiber communication,two-color laser cooling/trapping neutral atoms,optical filter,etc.