依托于学科优势的物理实验教学改革研究

通过改革和实践,提高了学生的学习主动性和创新能力,促进了教学科研的良性互动,实现了教学科研协同育人。     

铷原子饱和吸收光谱与偏振光谱对780nm半导体激光器稳频的比较

将激光频率锁定于合适的参考频率,可以有效地抑制激光器的频率起伏。本文采用铷原子D2线超精细跃迁线的饱和吸收光谱和偏振光谱分别获得鉴频曲线,通过电子伺服系统将频率校正信号负反馈到780 nm光栅外腔反馈半导体激光器外腔的压电陶瓷上的方法对激光器进行稳频。介绍了两种方法的基本原理和实验方案。与激光器自由运转300s时激光器典型的频率起伏约6.6 MHz相比,采用饱和吸收光谱和偏振光谱进行稳频,运转300 s时激光器典型的残余频率起伏分别约为1.5 MHz和0.6 MHz。分析表明,饱和吸收光谱稳频采用了相敏检波技术,需要对激光器进行频率调制,带来了额外的频率噪声,而偏振光谱稳频则是一种完全无频率调制的稳频方案。     

铷原子双共振激发态光抽运光谱及其在1.5μm半导体激光器稳频中的应用

本文介绍分别采用双共振光抽运(DROP)和光学双共振(OODR)光谱技术获得铷原子激发态5P_3/2-4D_3/2 (4D_5/2)之间的超精细跃迁光谱.与传统的OODR光谱相比,DROP光谱在信噪比、线宽等方面具有明显的优势.当1 529 nm光栅外腔半导体激光器的频率采用DROP光谱锁定于～87Rb原子的5P_3/2(F'=3) -4D_3/2(F"=3)超精细跃迁线时,300 s内典型的残余频率起伏为～0.65 MHz;明显优于采用OODR光谱锁频的结果(300 s内典型的残余频率起伏为～1.8 MHz).     

1560 nm连续光半导体激光器经PPLN倍频及经铷吸收光谱稳频

将激光器锁定到合适的参考频率上,可以有效地改变激光器的频率稳定性。1560 nm的分布反馈式半导体激光器,可以通过倍频锁定于铷原子吸收线上。实验中我们利用PPLN准位相匹配晶体进行倍频,当输入光为1.6 W时可以获得25 mW的倍频光,非线性转换系数为0.96%/W。我们还将激光器的频率锁定于Rb原子的吸收线上,30 s内剩余频率起伏约为±3.5 MHz。     

Autler-Townes doublet in the absorption spectra for the transition between excited states of cold cesium atoms

Autler-Townes splitting in absorption spectra of the excited states 6 2 P 3/2-8 2 S 1/2 of cold cesium atoms confined in a magneto-optical trap has been observed.Experimental data of the Autler-Townes splitting fit well to the dressed-atom theory,by which the fact of the cold atoms dressed by cooling/trapping laser beams is revealed.The results of the theoretical fitting with experiment not only told us the effective Rabi frequency cold atoms experienced,but also could be used for measuring the probability amplitudes of the dressed states.     

Off-resonant double-resonance optical-pumping spectra and their application in a multiphoton cesium magneto-optical trap

We present an investigation of double-resonance optical pumping(DROP) spectra under the condition of singlephoton frequency detuning based on a cesium 6S1/2–6P3/2–8S1/2ladder-type system with a room-temperature vapor cell.Two DROP peaks are found, and their origins are explored. One peak has a narrow linewidth due to the atomic coherence for a counterpropagating configuration; the other peak has a broad linewidth, owing to the spontaneous decay for a copropagating configuration. This kind of off-resonant DROP spectrum can be used to control and offset-lock a laser frequency to a transition between excited states. We apply this technique to a multiphoton cesium magneto-optical trap, which can efficiently trap atoms on both red and blue sides of the two-photon resonance.     

Extending a release-and-recapture scheme to single atom optical tweezer for effective temperature evaluation

By recording the fluorescence fraction of the cold atoms remaining in the magneto-optical trap (MOT) as a function of the release time,the release-and-recapture (R&R) method is utilized to evaluate the effective temperature of the cold atomic ensemble.We prepare a single atom in a large-magnetic-gradient MOT and then transfer the trapped single atom into a 1064-nm microscopic optical tweezer.The energy of the single atom trapped in the tweezer is further reduced by polarization gradient cooling (PGC) and the effective temperature is evaluated by extending the R&R technique to a single atom tweezer.The typical effective temperature of a single atom in the tweezer is improved from about 105 μK to about 17 μK by applying the optimum PGC phase.     

Single atoms transferring between a magneto-optical trap and a far-off-resonance optical dipole trap

Based on our work on single cesium atoms trapped in a large-magnetic-gradient vapour-cell magneto-optical trap (MOT),the signal-to-noise ratio (SNR) is remarkably improved.Also a far-off-resonance optical dipole trap (FORT) formed by a strongly-focused 1064 nm single frequency Nd:YVO 4 laser beam is introduced.One cesium atom is prepared in the MOT,and then it can transfer successfully between the MOT and the FORT which is overlapped with the MOT.Utilizing the effective transfer,the lifetime of single atoms trapped in the FORT is measured to be 6.9± 0.3 s.Thus we provide a system where the atomic qubit can be coherently manipulated.     

室温下铯原子气室中6P_(3/2)-8S_(1/2)激发态跃迁的速度选择光谱

以室温下的气室铯原子为介质,采用泵浦探测的方法获得激发态之间的光谱.在泵浦光与探测光相向、同向作用于铯原子得到的激发态超精细光谱有很大的差异.当考虑多普勒效应的影响,其分析结果与实验结果相一致.