Three-Dimensional Displacement Sensing has a very important demand in research fields such as nanomanufacturing, lithography, and microscopic imaging. Optical displacement sensing has received considerable attention in recent years due to the advantages of non-contact and high-precision, etc. However, traditional methods that use optical phase or polarization singularities to obtain position information are affected by the intensity of light, making the detection difficult. Here, we propose a nanoparticle on waveguide film structure that utilizes the nanoparticle as a near-field probe to achieve three-dimensional displacement sensing. The scattering light of the nanoparticle excites the resonance modes of the waveguide structure and projects the generated signal to the far field. The far-field distribution has a strong angular correlation, and by detecting the relative strength of the corresponding angle in the far-field distribution, it is possible to achieve three-dimensional displacement sensing. We have theoretically verified this idea through the finite difference time domain (FDTD) method. The three-dimensional displacement sensor implemented by this structure may be applied in nanometrology, nanofabrication, and super-resolution microscopes.
KEYWORDS: Nanoparticles, Metals, Near field, Silver, Scattering, Polarization, Plasmonics, Light scattering, Near field scanning optical microscopy, Near field optics
Surface plasmon polaritons (SPPs) play an important role in modern nanophotonics due to their vectorial characteristics, subwavelength scale and field enhancement natures. Up to now, a great deal of advanced scheme has been proposed to character the intensity distributions of SPPs, it remains challenging to achieve the measurement of the transverse and longitudinal fields of SPPs simultaneously with the NSOM probe. Here, we develop a technique for sorting the transverse and longitudinal field distributions of SPPs simultaneously with a metal-nanoparticle-on-film structure. The metal-nanoparticle-on-film structure was introduced as a near-field probe to couple the SPPs fields signals into far-field, of which the angular distribution is intensely polarization correlation. The imaging of the transverse and longitudinal fields with high precision can be achieved by collecting and analyzing the scattering signals which are caused by the horizontal and perpendicular polarization. The idea was validated theoretically by characterizing a complex SPPs field with the finite difference time-domain (FDTD) method. The proposed method realizes transverse and longitudinal field sorting of SPP field, and is conducive to the further study of the physical properties of SPP fields, for instance transverse spin, spin-orbit interaction, etc.
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