Storage of photon with orbital angular momentum based on an all-fiber system

我们在真空室中制备了具有最高透过率和约100 mW的高阶模(HOM)纳米光纤，这是在光纤表面附近捕获原子的重要一步。HOM纳米光纤被安装到真空系统中，通过光纤输出端口直接收集来自MOT中冷原子的荧光光子。通过在自由空间注入矢量光束，对该纳米光纤LP11群的各本征模进行了激发和分离。为了延长原子在光纤衰减场中的持续时间，我们利用偏振梯度冷却技术实现了原子在光纤中的有效温度降至数十UK。我们开发了LabVIEW程序来控制整个实验过程，通过测量导谐光束的原子吸收光谱，得到了不同模式下的相互作用强度。这为基于四波混频(FWM)的原子-纤维系统的轨道角动量(OAM)转移迈出了第一步。我们已经建立了用于四波混频过程中作为泵浦光束的激光系统。利用饱和吸收光谱或双光子吸收光谱将激光器的波长锁定在原子跃迁谱线上。在自由空间中已经获得了四波混频信号，但还没有在原子光纤系统中实现。

We have fabricated high-order modes(HOM) optical nanofibers with the highest possible transmission and taking ~ 100 mW in the vacuum chamber,which is a significant step towards atom trapping near fibre surface. HOM nanofibers have been installed into the vacuum system and fluorescence photons from cold atoms in the MOT were directly collected by the fibre output ports. Each eigenmodes of the LP11 group of this nanofiber have been excited and separated by injecting the vector beams in free space. In order to increase the duration time of atoms in the evanescent field of fibre, we have realized effective temperature of atoms in the MOT down to tens of uK by using polarization gradient cooling. We have developed LabVIEW programmes to control the whole experiment processing.The interaction strength for different modes have been obtained by measuring the atomic absorption spectra of the guided resonant beam. This make a first step towards the transfer of orbital angular momentum (OAM) in atom-fibre system based on four wave mixing(FWM). We have built the laser systems which will be used as pumping beams in four wave mixing process. The wavelength of lasers has been locked to atomic transition line by using saturated absorption spectroscopy or two photon absorption spectroscopy. The signal of FWM have been obtained in free space but we have not implemented in atom-fibre system.