We propose a controllable high-efficiency electrostatic surface trap for cold polar molecules on a chip by using two insulator-embedded charged rings and a grounded conductor plate. We calculate Stark energy structure pattern of ND3 molecules in an external electric field using the method of matrix diagonalization. We analyze how the voltages that are applied to the ring electrodes affect the depth of the efficient well and the controllability of the distance between the trap center and the surface of the chip. To obtain a better understanding, we simulate the dynamical loading and trapping processes of ND3 molecules in a ｜J, KM = ｜1,-1 state by using classical Monte–Carlo method. Our study shows that the loading efficiency of our trap can reach ～ 88%. Finally, we study the adiabatic cooling of cold molecules in our surface trap by linearly lowering the potential-well depth（i.e., lowering the trapping voltage）, and find that the temperature of the trapped ND3 molecules can be adiabatically cooled from 34.5 m K to ～ 5.8 m K when the trapping voltage is reduced from-35 k V to-3 k V.
Recently, there have been great interest and advancement in the field of laser cooling and magneto-optical trapping of molecules. The rich internal structure of molecules naturally lends themselves to extensive and exciting applications. In this paper, the radical 138Ba19F, as a promising candidate for laser cooling and magneto-optical trapping, is discussed in detail.The highly diagonal Franck-Condon factors between theX2∑＋1/2and A2∏1/2states are first confirmed with three different methods. Afterwards, with the effective Hamiltonian approach and irreducible tensor theory, the hypertine structure of theX2∑＋1/2state is calculated accurately. A scheme for laser cooling is given clearly. Besides, the Zeeman effects of the upper （ A2∏1/2）andlower（X2∑＋1/2）levels are also studied, and their respective g factors are obtained under a weak magnetic field. Its large g factor of the upper stateA2∏1/2is advantageous for magneto-optical trapping. Finally, by studying Stark effect of BaFin theX2∑＋1/2, we investigate the dependence of the internal effective electric field on the applied electric field. It is suggested that such a laser-cooled BaF is also a promising candidate for precision measurement of electron electric dipole moment.
A simple model is developed to study the laser cooling of solids.The condition of laser cooling of a solid is developed.By using some parameters of the Yb 3＋ ion,which is most widely used in laser cooling,we then calculate the cooling power and the cooling efficiency.In order to make a more precise analysis, the effect of fluorescent reabsorption,which is unavoidable in the cooling process,is discussed using the random walk model.Taking Tm 3＋ ion as an example,we derive the average number of absorption events and determine the change in quantum efficiency due to reabsorption.Finally,we obtain the red-shift of the fluorescent wavelength and the requirement of sample dimension.
An electrostatic trap for polar molecules is proposed. Loading and trapping of polar molecules can be realized by applying different voltages to the two electrodes of the trap. For ND3 molecular beams centered at -10 m/s, a high loading efficiency of -67% can be obtained, as confirmed by our Monte Carlo simulations. The volume of our trap is as large as ,-3.6 cm3, suitable for study of the adiabatic cooling of trapped molecules. Our simulations indicate that trapped ND3 molecules can be cooled from -23.3 mK to 1.47 mK by reducing the trapping voltages on the electrodes from 50.0 kV to 1.00 kV.
报道了波长为1015 nm的大功率单频半导体光放大器的设计与研制,实验研究了不同注入光功率和不同温度下,放大器输出光功率与注入电流的依赖关系。结果表明:当波长为1015 nm、功率约为30 m W的种子光注入到半导体激光放大系统中,并把该放大器的注入电流增加到5 A时,其输出的激光功率高达1600 m W,相应的放大倍数可达17.3 d B,且放大器输出功率随温度的降低而增大。此外,还观测了半导体光放大器输出功率的稳定性,发现该放大器可长时间保持稳定工作。因此,该1015 nm激光放大系统可用于掺杂稀土离子晶体的激光冷却,四倍频后还可用于汞原子光钟的实验研究。
