We report three orders of magnitude optical cooling of the fundamental torsional mode of a 5 mm long, 550 nm diameter optical nanofiber. The rotation of the nanofiber couples to the polarization of guided laser fields. We use a weak laser probe to monitor the rotation and use feedback to modulate the polarization of an auxiliary drive laser providing torque. Our results present a tool for the optomechanical control of large-scale torsional resonators, with metrological applications and potential implications for studying macroscopic objects in quantum states.

为实现对危化品气体泄漏的实时、远距离、非接触性监测，提高监测效率和精度，研制了一种多组分气体激光遥测系统。基于波长调制光谱技术，利用STM32芯片结合自主设计的驱动电路对激光器进行控制，采用不同的调制频率分别提取甲烷、氨气、乙炔的二次谐波信号，实现混合气体的同步、实时、远距离遥测。采用光强调制幅度归一化的波长调制光谱技术使遥测结果免受回波激光对信号强度的影响。实验测量表明本系统对甲烷、氨气、乙炔的探测下限分别可以达到87 ppm·m、212 ppm·m、12 ppm·m，测量误差小于10%。测量不同距离下的遥测信号，遥测距离至少可达40 m。本系统为激光痕量气体检测研究与应用提供了一种多气体、实时、同步、高灵敏度、远距离、性能稳定的遥测解决方案，能够广泛应用于矿山灾害气体监测预警，危化品场站和运输管网等场合的气体泄漏监测预警。

We demonstrate the optomechanical cooling of a tapered optical nanofiber by coupling the polarization of light to the mechanical angular momentum of the system. The coupling is enabled by birefringence in the fiber and does not make use of an optical resonator. We find evidence for cooling in the distribution of thermally driven amplitude fluctuations and the noise spectrum of the torsional modes. Our proof-of-principle demonstration shows cavity-less cooling of the torsional degree of freedom of a macroscopically extended nanofiber.

We report the experimental realization of dark state atoms trapping in a nanofiber optical lattice. By applying the magic-wavelength trapping potentials of cesium atoms, the AC Stark shifts are strongly suppressed. The dark magneto-optical trap efficiently transfers the cold atoms from bright (6S_1/2, F = 4) into dark state (6S_1/2, F = 3) for hyperfine energy levels of cesium atoms. The observed transfer efficiency is as high as 98% via saturation measurement. The trapping lifetime of dark state atoms trapped by a nanofiber optical lattice is also investigated, which is the key element for realizing optical storage. This work contributes to the manipulation of atomic electric dipole spin waves and quantum information storage for fiber networks.

We report the observation of ultralow-power absorption saturation in a tapered optical fiber (TOF) mounted in a hot cesium (Cs) vapor in a vacuum chamber. The small optical mode area of TOF produces a great influence on optical properties, allowing optical interactions with nanowatt-level power. The comparison of transmission characteristics for the TOF system and free-space vapor is investigated at different input power and atomic density. The unique performance of the Cs-TOF system makes it a promising candidate in resonant nonlinear optical applications with ultralow power.

We present a simple, robust, space-adjustable dark magneto-optical trap (MOT) for the efficient production of heteronuclear molecules. Double-mixed beams made up of repumping beams and depumping beams propagate in nearly opposite directions in the dark MOT. This optical arrangement can easily adjust the spatial positions of two clouds by changing the power ratio of the two repumping beams, and ensure a good overlap, which is very necessary for the production of heteronuclear molecules. The imaging of cold atoms by camera and the collision-induced loss rate obtained by recording the loading curve of the cold atoms show that we obtain a perfect overlap of atom clouds. The number of RbCs molecules with the double-mixed beams is improved by 70%, which is higher than the one with the single-mixed beam.