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Generation of a sub-diffraction hollow ring by shaping an azimuthally polarized wave

View Article: PubMed Central - PubMed

ABSTRACT

The generation of a sub-diffraction optical hollow ring is of great interest in various applications, such as optical microscopy, optical tweezers, and nanolithography. Azimuthally polarized light is a good candidate for creating an optical hollow ring structure. Various of methods have been proposed theoretically for generation of sub-wavelength hollow ring by focusing azimuthally polarized light, but without experimental demonstrations, especially for sub-diffraction focusing. Super-oscillation is a promising approach for shaping sub-diffraction optical focusing. In this paper, a planar sub-diffraction diffractive lens is proposed, which has an ultra-long focal length of 600 λ and small numerical aperture of 0.64. A sub-diffraction hollow ring is experimentally created by shaping an azimuthally polarized wave. The full-width-at-half-maximum of the hollow ring is 0.61 λ, which is smaller than the lens diffraction limit 0.78 λ, and the observed largest sidelobe intensity is only 10% of the peak intensity.

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The (a) 3D and (b) 2D color maps of the measured optical intensity on the focal plane; the optical intensity distribution along the (c) x-axis and (b) y-axis.
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f6: The (a) 3D and (b) 2D color maps of the measured optical intensity on the focal plane; the optical intensity distribution along the (c) x-axis and (b) y-axis.

Mentions: The focal plane was found to be approximately 380 μm (600.5 λ), which was similar to the theoretically predicted value of 600 λ and the COMSOL simulation result of 599.8 λ. Figure 6(a,b) give the 3D and 2D color maps of the optical intensity measured on the focal plane, which show a clear hollow ring structure. Due to the difficulties in the optical alignment mentioned above, the focal hollow ring was not symmetrical. The optical intensity varied around the circumference of the central peak lobe. To evaluate the size of the hollow ring, the normalized intensity distribution was plotted along the x direction and y direction across the center of the hollow ring in Fig. 6(c,d), respectively. The peak-peak diameter of the hollow ring was 1.19 λ and 1.14 λ in the x direction and y direction, respectively, and these values are quite close to the value of 1.16 λ obtained in the COMSOL simulation, depicted in Fig. 3(b). For further comparison, the normalized COMSOL simulation result is also given in the Fig. 6(c,d).


Generation of a sub-diffraction hollow ring by shaping an azimuthally polarized wave
The (a) 3D and (b) 2D color maps of the measured optical intensity on the focal plane; the optical intensity distribution along the (c) x-axis and (b) y-axis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120339&req=5

f6: The (a) 3D and (b) 2D color maps of the measured optical intensity on the focal plane; the optical intensity distribution along the (c) x-axis and (b) y-axis.
Mentions: The focal plane was found to be approximately 380 μm (600.5 λ), which was similar to the theoretically predicted value of 600 λ and the COMSOL simulation result of 599.8 λ. Figure 6(a,b) give the 3D and 2D color maps of the optical intensity measured on the focal plane, which show a clear hollow ring structure. Due to the difficulties in the optical alignment mentioned above, the focal hollow ring was not symmetrical. The optical intensity varied around the circumference of the central peak lobe. To evaluate the size of the hollow ring, the normalized intensity distribution was plotted along the x direction and y direction across the center of the hollow ring in Fig. 6(c,d), respectively. The peak-peak diameter of the hollow ring was 1.19 λ and 1.14 λ in the x direction and y direction, respectively, and these values are quite close to the value of 1.16 λ obtained in the COMSOL simulation, depicted in Fig. 3(b). For further comparison, the normalized COMSOL simulation result is also given in the Fig. 6(c,d).

View Article: PubMed Central - PubMed

ABSTRACT

The generation of a sub-diffraction optical hollow ring is of great interest in various applications, such as optical microscopy, optical tweezers, and nanolithography. Azimuthally polarized light is a good candidate for creating an optical hollow ring structure. Various of methods have been proposed theoretically for generation of sub-wavelength hollow ring by focusing azimuthally polarized light, but without experimental demonstrations, especially for sub-diffraction focusing. Super-oscillation is a promising approach for shaping sub-diffraction optical focusing. In this paper, a planar sub-diffraction diffractive lens is proposed, which has an ultra-long focal length of 600 λ and small numerical aperture of 0.64. A sub-diffraction hollow ring is experimentally created by shaping an azimuthally polarized wave. The full-width-at-half-maximum of the hollow ring is 0.61 λ, which is smaller than the lens diffraction limit 0.78 λ, and the observed largest sidelobe intensity is only 10% of the peak intensity.

No MeSH data available.


Related in: MedlinePlus