间接泵浦激发态原子滤光器研究

Atomic filters are kind of optical spectrum filter taking use of atomic transition lines. By the very narrow linewidth of atomic spectrum, it can choose signal within very narrow bandwidth while filter out noises out of band, and thus increase the signal to noise ratio. Atomic filters has potentials in free space optical communication, optical imaging, lidar, and quantum key distribution in free space. The working wavelength of atomic filter depends on the transition lines of corresponding atoms. Atoms usually stays at ground state. Since wavelengths of transitions from ground state to excited state are so few that the applications of atomic filters are significantly limited. Thus the excited state atomic filters using transitions between excited states are proposed. Although the choices of wavelengths are greatly expanded, there are still limitations for excited state atomic filters. The atoms must be optically pumped to the target excited state and this pumping process must obey the selection rules of electric dipole transition, otherwise the low efficient two-photon pumping or cascade lasers are required and the system could be very complicated and unstable. In this project, we proposed an indirect pumping method for excited state atomic filter to solve the electric dipole transition rule problem. Based on this method, this limitation could be well solved and the applications of atomic filters can be extended to near infrared and even middle infrared domain.

原子滤光器是利用原子能级间跃迁的精细光谱实现超窄带宽滤光功能的器件，用以滤出极窄带宽内的信号并隔离带外噪声，从而提高信噪比。它在空间光通信、光学成像、激光雷达、空间量子密钥分发等领域具有良好的应用前景。原子滤光器的工作波长取决于原子能级间跃迁的特征波长。通常原子处于基态，从基态到激发态的跃迁波长选择很少，极大地限制了原子滤光器的应用范围。为了拓展其应用范围，需要发展激发态原子滤光器，利用激发态之间跃迁能够提供更多的波长选择。激发态原子滤光器需要将原子通过光泵浦抽运到激发态，抽运过程必须满足电偶极跃迁选择定则，不满足选择定则的下能级往往需要采用低效率的双光子泵浦方法或者采用两台激光器级联泵浦，系统复杂且不稳定，严重制约了激发态FADOF的发展。本项目提出了一种间接泵浦的激发态原子滤光器方案，能够有效解决上述瓶颈问题，从而推动原子滤光器往近红外乃至中红外波段的应用，具有重要的应用价值。

原子滤光器是利用原子能级间跃迁的精细光谱实现超窄带宽滤光功能的器件，用以滤出极窄带宽内的信号并隔离带外噪声，从而提高信噪比。它在空间光通信、光学成像、激光雷达、空间量子密钥分发等领域具有良好的应用前景。原子滤光器的工作波长取决于原子能级间跃迁的特征波长。通常原子处于基态，从基态到激发态的跃迁波长选择很少，极大地限制了原子滤光器的应用范围。为了拓展其应用范围，需要发展激发态原子滤光器，利用激发态之间跃迁能够提供更多的波长选择。.本项目针对激发态原子滤光器波长受限的问题，提出间接泵、空心阴极灯等一系列方案，并完成了多种激发态原子滤光器的实验及其比对，有效推动原子滤光器往近红外乃至中红外波段的应用。具体的：1）完成了激发态Faraday原子滤光器理论分析，对涉及泵浦过程的激发态原子滤光器的设计和分析具有科学意义；2）首次实现了激发态Voigt原子滤光器，对大视场角需求下的滤光成像系统具有实用价值；3）实现了利用空心阴极灯实现原子滤光器的新方法，对大幅拓展原子滤光器的可选择元素范围及波段具有重要意义；4）提出了基于阴极灯的激发态的原子滤光器新方案，激发态原子滤光器的发展提供了新的技术路线。本项目共发表SCI论文6篇，申请专利2项（已受理），完成了主要研究任务。