ABSTRACT

We studied non-resonant two photon absorption (NRTPA) 5S_1/2→5D_5/2 of hot Rb atom using a laser emitting at 778nm. The decay channel 5D_5/2→6P_3/2→5S_1/2 is monitored to record the blue fluorescence. Two important aspects of blue fluorescence are explored: (i) photon number statistics under counter-propagating beam geometry, (ii) extraction of a workable discriminator signal by using modulation transfer for offset locking. The blue photon statistics histogram closely follows super–Poissonian distribution revealing the partially coherent or chaotic character under the limit of large photon counts. On the other hand modulation amplitude vs. peak height of 1-st derivative signal reveals that too small or too large modulation is detrimental for extracting discriminator signal. Under weak modulation, the offset stabilized laser attains square root of Allan variance σ(τ) ∼ 1.5 × 10⁻¹⁰ at integration time τ>10s. We propose generation of an offset stabilized chaotic blue light source by coupling (i) and (ii).

摘要

我们使用在778nm处发射的激光研究了热Rb原子的非共振两光子吸收（NRTPA）5S _1/2 →5D _5/2。衰减通道5D _5/2 →6P _3/2 →5S _1/2监测以记录​​蓝色荧光。探索了蓝色荧光的两个重要方面：（i）在反向传播的光束几何结构下的光子数统计，（ii）通过使用用于偏移锁定的调制传递来提取可行的鉴别器信号。蓝色光子统计直方图紧随超泊松分布，揭示了在大光子数的限制下部分相干或混沌的特征。另一方面，一阶导数信号的调制幅度与峰值高度的关系表明，太小或太大的调制对于提取鉴别器信号都是有害的。在弱调制下，偏移稳定激光器获得的艾伦方差的平方根σ（τ）〜1.5×10 ^-10在积分时间τ> 10s时。我们建议通过耦合（i）和（ii）生成偏移稳定的混沌蓝色光源。