掺铒光纤光梳在镱原子光钟中的应用

发布时间：2019-05-23 15:39

【摘要】：冷镱原子光钟是近年来国际原子频标研究领域的热点,镱原子需要经过399nm磁光阱一级激光冷却和556nm磁光阱二级激光冷却并装载至光晶格来探测其钟跃迁谱线。为了获得高信噪比的冷镱原子钟跃迁谱,需要采用归一化探测的方法,即使用649nm770nm抽运光将寿命较长的3p0态原子抽运回到基态。抽运光是钟跃迁信号探测的重要组成部分,为了获得稳定高效的抽运效率,649nm770nm激光频率的稳定就显得非常重要。光学频率梳提供高分辨率,高精度,高精度的频率标准。特别是光纤光梳,具有体积小、集成度高、易于维护、自锁模、运行成本低等一系列优势。可以将649nm770nm连续激光器同时锁定在光梳上以达到稳频效果。本文探索了激光的锁模原理以及不同的锁模技术,利用非线性偏振旋转(NPR)锁模技术成功搭建了工作在不同色散区域的1550nm掺铒光纤激光器。通过对腔内偏振态的控制,利用双折射滤波效应我们获得了工作在零色散附近的多波长激光,在3dB带宽内有50个波长间隔为0.8nm的多波长序列。在呼吸脉冲锁模状态下,获得稳定的自锁模超短脉冲激光,并且通过电子电路反馈系统将64.399MHz的重复频率稳定在晶振漂移的范围。我们利用啁啾脉冲放大技术并结合双向泵浦的方式,将3.4mW的种子脉冲光放大至210mW左右,其脉冲宽度也从展宽后的1.94ps压缩至200fs以下,将放大后的脉冲光谱展宽。基于广义非线性薛定谔方程,我们利用分布式傅里叶积分的方法研究了不同类型的HNLF对于超连续谱展宽的影响,为后续光梳零频的获得和锁定提供了实验依据,并且为最终将649nm和770nm抽运光频率同时锁定在掺铒光纤光梳上打下了基础。
[Abstract]:Cold ytterbium atomic optical clock is a hot spot in the field of international atomic frequency standard research in recent years. Ytterbium atom needs to be cooled by 399nm magneto-optical trap first-class laser and 556nm magneto-optical trap secondary laser cooling and loaded into optical lattice to detect its clock transition spectrum line. In order to obtain the clock transition spectrum of cold ytterbium atom with high signal-to-noise ratio (SNR), it is necessary to use the normalization detection method, even if the long-lived 3p0 state atom is pumped back to the ground state by 649nm770nm pumping light. Pumping light is an important part of clock transition signal detection. In order to obtain stable and efficient pumping efficiency, the stability of 649nm770nm laser frequency is very important. Optical frequency comb provides high resolution and high precision frequency standard. Especially, optical fiber comb has a series of advantages, such as small volume, high integration, easy maintenance, self-mode locking, low operation cost and so on. The 649nm770nm continuous laser can be locked on the optical comb at the same time to achieve the effect of frequency stabilization. In this paper, the mode-locking principle of laser and different mode-locking techniques are explored. 1550nm erbium-doped fiber lasers working in different dispersion regions are successfully built by using nonlinear polarization rotating (NPR) mode-locking technology. By controlling the polarization state in the cavity, we obtain a multi-wavelength laser working near zero dispersion by using the birefringent filtering effect. There are 50 multi-wavelength sequences with 0.8nm wavelength interval in the 3dB bandwidth. Under the condition of respiratory pulse mode-locking, a stable self-mode-locked ultra-short pulse laser is obtained, and the repetition frequency of 64.399MHz is stabilized in the range of crystal oscillator drift by electronic circuit feedback system. By using chirped pulse amplification technique and bidirectional pumping method, the seed pulse light of 3.4mW is amplified to about 210mW, and the pulse width is compressed from the widened 1.94ps to below 200fs, and the amplified pulse spectrum is widened. Based on the generalized nonlinear Schrodinger equation, we use the distributed Fourier integral method to study the effects of different types of HNLF on the broadening of supercontinuum spectrum, which provides an experimental basis for the subsequent acquisition and locking of zero frequency of light comb. It also lays a foundation for locking the 649nm and 770nm pumping light frequencies on the erbium-doped fiber comb at the same time.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN248

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