Dahiya Sunil, Tyagi Akansha, Mandal Ankur, Pfeifer Thomas, Singh Kamal P
Department of Physical Sciences, Indian Institute of Science Education and Research Mohali, Sector 81, Mohali, 140306, India.
Max Planck Institute for Nuclear Physics, 69117, Heildelberg, Germany.
Sci Rep. 2022 May 23;12(1):8656. doi: 10.1038/s41598-022-12620-8.
White light interferometry is a well established technique with diverse precision applications, however, the conventional interferometers such as Michelson, Mach-Zehnder or Linnik are large in size, demand tedious alignment for obtaining white light fringes, require noise-isolation techniques to achieve sub-nanometric stability and importantly, exhibit unbalanced dispersion causing uncertainty in absolute zero delay reference. Here, we demonstrate an ultrathin white light interferometer enabling picometer resolution by exploiting the wavefront division of a broadband incoherent light beam after transmission through a pair of micrometer thin identical glass plates. Spatial overlap between the two diffracted split wavefronts readily produce high-contrast and stable white light fringes, with unambiguous reference to absolute zero path-delay position. The colored fringes evolve when one of the ultrathin plates is rotated to tune the interferometer with picometric resolution over tens of μm range. Our theoretical analysis validates formation of fringes and highlights self-calibration of the interferometer for picoscale measurements. We demonstrate measurement of coherence length of several broadband incoherent sources as small as a few micrometer with picoscale resolution. Furthermore, we propose a versatile double-pass configuration using the ultrathin interferometer enabling a sample cavity for additional applications in probing dynamical properties of matter.
白光干涉测量法是一种成熟的技术，有着各种精密应用，然而，诸如迈克尔逊、马赫-曾德尔或林尼克等传统干涉仪体积庞大，获取白光条纹需要繁琐的校准，需要噪声隔离技术来实现亚纳米级的稳定性，并且重要的是，存在色散不平衡问题，导致绝对零延迟参考存在不确定性。在此，我们展示了一种超薄白光干涉仪，通过利用宽带非相干光束透过一对微米级厚度的相同玻璃板后的波前分割，实现了皮米级分辨率。两个衍射分裂波前之间的空间重叠很容易产生高对比度和稳定的白光条纹，并且能明确参考绝对零光程延迟位置。当其中一块超薄板旋转以在数十微米范围内以皮米级分辨率调节干涉仪时，彩色条纹会发生变化。我们的理论分析验证了条纹的形成，并突出了干涉仪用于皮米级测量的自校准特性。我们展示了对几个宽带非相干光源的相干长度进行测量，这些光源的相干长度小至几微米，分辨率达到皮米级。此外，我们提出了一种使用超薄干涉仪的通用双程配置，该配置可实现一个样品腔，用于探测物质动态特性等更多应用。
