High-Resolution Quantitative Phase Imaging of Plasmonic Metasurfaces with Sensitivity down to a Single Nanoantenna

Abstract

Optical metasurfaces have emerged as a new generation of building blocks for multi-functional optics. Design and realization of metasurface elements place ever-increasing demands on accurate assessment of phase alterations introduced by complex nanoantenna arrays, a process referred to as quantitative phase imaging. Despite considerable effort, the widefield (non-scanning) phase imaging that would approach resolution limits of optical microscopy and indicate the response of a single nanoantenna still remains a challenge. Here, we report on a new strategy in incoherent holographic imaging of metasurfaces, in which unprecedented spatial resolution and light sensitivity are achieved by taking full advantage of the polarization selective control of light through the geometric (Pancharatnam-Berry) phase. The measurement is carried out in an inherently stable common-path setup composed of a standard optical microscope and an add-on imaging module. Phase information is acquired from the mutual coherence function attainable in records created in broadband spatially incoherent light by the self-interference of scattered and leakage light coming from the metasurface. In calibration measurements, the phase was mapped with the precision and spatial background noise better than 0.01 rad and 0.05 rad, respectively. The imaging excels at the high spatial resolution that was demonstrated experimentally by the precise amplitude and phase restoration of vortex metalenses and a metasurface grating with 833 lines/mm. Thanks to superior light sensitivity of the method, we demonstrated, for the first time to our knowledge, the widefield measurement of the phase altered by a single nanoantenna, while maintaining the precision well below 0.15 rad.

Single-Shot Three-Dimensional Orientation Imaging of Nanorods Using Spin to Orbital Angular Momentum Conversion

“…The orientation imaging procedure described above was experimentally tested using a benchmark sample composed of two rows of gold nanorods (length 200 nm, width 80 nm, height 30 nm), fabricated by electron beam lithography onto a silicon substrate. 42 Nanorods placed in the first row were gradually rotated by 22.5°, while all nanorods in the second row kept a constant orientation angle (see scanning electron microscope images in Fig. 3A).…”

Advantages of Fresnel biprism-based digital holographic microscopy in quantitative phase imaging

“…Future work will involve the evaluation of the birefringence sensing using a benchmark birefringence target with known thickness and birefringence or a spatial light modulator to mimic one as in Ref. 22 . After this validation, further studies using several biological specimens will also be performed to evaluate the potential of this system for biological imaging.…”

“…Ultimately, PS imaging systems are advantageous in biological imaging increasing the understanding of cell biological processes 21 – 24 since they determine the isotropic properties of different cellular and extracellular molecular components, such as microtubules and amyloid. 21 …”

Fast photothermal spatial light modulation for quantitative phase imaging at the nanoscale

“…This approach, established as quantitative phase imaging (QPI), has become a powerful tool for capturing phase images of transparent samples in a transmission configuration, including high-resolution 3D profiling of single cells 6 and mapping the phase of opaque structures in a reflection configuration 7 . QPI has already reached the sensitivity to image the displacement of nanostructures at video-rates 8 , 9 and specific applications in plasmonic imaging have allowed characterization of nanoscopic patterns 10 , 11 . However higher sensitivity and speed of QPI remain limited by the performance of the available spatial light modulation techniques.…”