Photonic Spin-Hall Differential Microscopy

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Photonic Spin-Hall Differential Microscopy

Ruisi Wang, Shanshan He, and Hailu Luo

Phys. Rev. Applied 18, 044016 – Published 6 October 2022

Abstract

The visualization of transparent phase objects such as living cells and tissues plays an important role in biological research. Transparency and invisibility caused by weak scattering and absorption make it challenging to image phase objects. Here, we propose differential microscopy based on the photonic spin Hall effect at a simple glass interface. We find that the photonic spin Hall effect can perform a spatial differentiation operation on the phase distribution, and therefore is extremely sensitive to the structures of phase objects. By incorporating this into a bright-field microscope, high-contrast images of pure phase objects can be achieved. We further reconstruct the phase distribution by biased imaging, which provides potential possibilities for high-resolution reconstruction and quantitative analysis of phase images. Compared with the conventional differential-interference-contrast microscope, which requires the introduction of complicated phase-contrast devices into a bright-field microscope, our proposed photonic spin-Hall differential microscopy requires only a simple glass interface. The combination of the photonic spin Hall effect and a bright-field microscope enables compact and low-cost differential microscopy, which may lead to important applications in versatile and high-contrast biological imaging.

Received 14 April 2022
Revised 28 July 2022
Accepted 15 August 2022

DOI:https://doi.org/10.1103/PhysRevApplied.18.044016

Physics Subject Headings (PhySH)

Angular momentum of light Spin Hall effect Spin-orbit coupling Topological effects in photonic systems

Biological materials Optical sources & detectors

Polarization

Phase contrast optical microscopy

Atomic, Molecular & OpticalCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Ruisi Wang, Shanshan He, and Hailu Luo ^*

Laboratory for Spin Photonics, School of Physics and Electronics, Hunan University, Changsha 410082, China

^*hailuluo@hnu.edu.cn

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Vol. 18, Iss. 4 — October 2022

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Images

Figure 1
Phase-contrast imaging based on the photonic SHE. (a) The photonic SHE occurs at a glass interface and exhibits spin-dependent shifts along the $y$ direction. (b) Purely geometric features of polarization evolution in momentum space. (c) Theoretical results for spatial spectral transfer function. (d) Input pure phase distribution. (e) Theoretical differential image corresponding to (d). (f) Intensity distribution of edge image (e) along the direction of the vertical white dashed line.
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Figure 2
Imaging experiment on transparent glass pattern. (a) Experimental setup. The laser generates a Gaussian beam. GLP, Glan laser polarizer. L1–L4, lenses with focal lengths of $50$ , $75$ , $175$ , and $250 mm$ , respectively. The refractive index of the prism is $n = 1.515$ . CCD, charge-coupled device. The inset shows a photograph of the phase sample ( $50 mm$ in diameter). (b) SEM image of a portion of the sample etching depth. (c) SEM image of a portion of the sample surface. (d) Bright-field images. (e) Differential images. (f),(g) Light intensity distributions in each pixel along the white dashed lines in (d),(e), respectively.
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Figure 3
Microscopic imaging experiment on quantitative-phase-microscopy targets. (a) Experimental setup for photonic spin-Hall differential microscopy. The objective has a magnification of $10 \times$ , and its numerical aperture is 0.25. The focal lengths of L1, L2, L3, and L4 are $125$ , $150$ , $175$ , and $250 mm$ , respectively. The insets in (a) are SEM images of a 350-nm focus star on the resolution target. (b) Photograph of the phase target. (c) Relationship between the horizontal-direction intensity of five edge images and the phase gradient of five focus-star targets. (d) Images of targets 1–5 selected from user report for quantitative-phase-microscopy target. (e),(f) Bright-field and differential images of the quantitative-phase target. (g) Intensity curves corresponding to the white lines across the edge images in (f).
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Figure 4
Microscopic imaging experiment on unlabeled biological cells. Bright-field and differential images obtained with laser sources emitting at (a)–(d) $632.8 nm$ and (i)–(l) $532 nm$ . (a),(b) Bright-field and differential images of unlabeled onion cells. (c),(d) Bright-field and differential images of unlabeled scallion cells. (e)–(h) Intensity curves corresponding to the white dashed lines across images (a)–(d), respectively. (i)–(p) Corresponding results with the laser source emitting at $532 nm$ .
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Figure 5
Reconstructed phase of quantitative-phase-microscopy targets. (a), (b) Derivatives of the phase distribution with respect to the y and x axes in 350-nm target, respectively, which are calculated from bias retardations of $\pm {0.8}^{\circ}$ based on horizontal and vertical edge images. (c), (d) Derivatives of the phase distribution with respect to the y and x axes in 250-nm target, respectively, which are calculated from bias retardations of $\pm {0.8}^{\circ}$ based on horizontal and vertical edge images. (e) Vector superposition of (a), (b). (f) Reconstructed phase distribution $φ (x, y)$ in 350-nm target. (g) Vector superposition of (c) and (d). (h) Reconstructed phase distribution $φ (x, y)$ in 250-nm target. (i)–(l) Intensity cross sections along the white lines in (e)–(h). The blue lines indicate the averaged experimental data.
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