Large field-of-view holographic imager with ultra-high phase sensitivity using multi-angle illumination

Quantitative phase imaging and holography allow highly sensitive detection of phase changes, for example of surface non-uniformities or refractive index (RI) structures in the volume of a sample. For many applications, wide field-of-view (FoV) and high phase sensitivity are required. Lens-free interferometric microscopy can op-erate over a wide FoV and volume, but with the drawbacks of low axial resolution and poor optical sectioning, which comes with increased noise from out-of-focus planes. In this work, we propose and demonstrate a novel implementation of lens-free phase imaging with phase-shifting interferometry and multi-angle illumination that enhances axial resolution and image quality, enabling ultra-high phase sensitivity with optical path difference (OPD) background root-mean-square (RMS) noise of 0.2 nm, while operating over a wide FoV ( > 10 mm2). As a prototypical application, we demonstrate imaging of 10 nm thin transparent glass structures, and of 3D laser-written structures of RI modifications in glass over a large volume ( > 10 mm3), where the location of features along the z-axis can be determined with 3x higher accuracy compared to an on-axis illumination. The technology is particularly suitable for large-scale analysis and characterization of structures on the surface or embedded in transparent materials.

Automated summary

Quantitative phase imaging and holography can detect phase changes with high sensitivity, such as surface non-uniformities or refractive index structures in a sample. This work proposes and demonstrates a novel lens-free phase imaging technique, utilizing phase-shifting interferometry and multi-angle illumination, to enhance axial resolution and image quality, achieving ultra-high phase sensitivity.