Li Zeyu, Yan Qiang, Qin Yu, Kong Weipeng, Li Guangbin, Zou Mingrui, Wang Du, You Zhisheng, Zhou Xun
Opt Express. 2019 Jan 21;27(2):702-713. doi: 10.1364/OE.27.000702.
We demonstrate terahertz (THz) lens-free in-line holography on a chip in order to achieve 40 μm spatial resolution corresponding to ~0.7λ with a numerical aperture of ~0.87. We believe that this is the first time that sub-wavelength resolution in THz holography and the 40 μm resolution were both far better than what was already reported. The setup is based on a self-developed high-power continuous wave THz laser at 5.24 THz (λ = 57.25 μm) and a high-resolution microbolometer detector array (640 × 512 pixels) with a pitch of 17 μm. This on-chip in-line holography, however, suffers from the twin-image artifacts which obfuscate the reconstruction. To address this problem, we propose an iterative optimization framework, where the conventional object constraint and the L sparsity constraint can be combined to efficiently reconstruct the complex amplitude distribution of the sample. Note that the proposed framework and the sparsity-based algorithm can be applied to holography in other wavebands without limitation of wavelength. We demonstrate the success of this sparsity-based on-chip holography by imaging biological samples (i.e., a dragonfly wing and a bauhinia leaf).
我们展示了芯片上的太赫兹（THz）无透镜同轴全息术，以实现40μm的空间分辨率，对应于约0.7λ，数值孔径约为0.87。我们认为，这是首次在太赫兹全息术中实现亚波长分辨率，且40μm的分辨率远优于已报道的结果。该装置基于自行研制的5.24THz（λ = 57.25μm）高功率连续波太赫兹激光器和间距为17μm的高分辨率微测辐射热计探测器阵列（640×512像素）。然而，这种芯片上的同轴全息术存在孪生图像伪影，会干扰重建。为了解决这个问题，我们提出了一个迭代优化框架，其中传统的物体约束和L稀疏约束可以结合起来，有效地重建样品的复振幅分布。请注意，所提出的框架和基于稀疏性的算法可以应用于其他波段的全息术，而不受波长限制。我们通过对生物样品（即蜻蜓翅膀和紫荆叶）成像，证明了这种基于稀疏性的芯片上全息术的成功。
