论文标题
精确数字全息原子样品平面的光谱定位
Spectroscopic localization of atomic sample plane for precise digital holography
论文作者
论文摘要
在数字全息图中，连贯的散射光场可以体积重建。通过将磁场重新聚焦于样品平面，可以同时推断出3D的样品的吸收和相移谱。这种全息优势对于冷原子样品的光谱成像非常有用。但是，与（例如生物样品或固体颗粒）不同，激光冷却下的准热原子气体通常是无特征的，而没有尖锐的边界，使一类标准的数值重新关注方法无效。在这里，我们扩展了基于小相异常的重新聚焦协议，以使小相对象以游离原子样本。有了对探针条件变化的冷原子的相干光谱相位角关系的先验知识，可以可靠地识别出原子样品的``相位外''响应'''''''''响应'''''''反应''响应，可以可靠地识别出在数字背部跨样品平面上的符号，以用作重新定位标准。在实验上，我们确定了从微观偶极子陷阱释放的激光冷却$^{39} $ k气体的样品平面，其$Δz\ of 1〜 {\ rmμm} $μm} $ \ ll2λ_p/{\ rm na} $λ_p= 770〜 $ nm探针波长。
In digital holography, the coherent scattered light fields can be reconstructed volumetrically. By refocusing the fields to the sample planes, absorption and phase-shift profiles of sparsely distributed samples can be simultaneously inferred in 3D. This holographic advantage is highly useful for spectroscopic imaging of cold atomic samples. However, unlike (e.g., biological samples or solid particles), the quasi-thermal atomic gases under laser-cooling are typically featureless without sharp boundaries, invalidating a class of standard numerical refocusing methods. Here, we extend the refocusing protocol based on the Gouy phase anomaly for small phase objects to free atomic samples. With a prior knowledge on a coherent spectral phase angle relation for cold atoms that is robust against probe condition variations, an ``out-of-phase'' response of the atomic sample can be reliably identified, which flips the sign during the numeric back-propagation across the sample plane to serve as the refocus criterion. Experimentally, we determine the sample plane of a laser-cooled $^{39}$K gas released from a microscopic dipole trap, with a $δz\approx 1~{\rm μm}$$\ll 2λ_p/{\rm NA}^2$ axial resolution, with a NA=0.3 holographic microscope at $λ_p=770~$nm probe wavelength.
