We use the concepts from nano-optics, mainly directional scattering to develop techniques that can be used in high precision metrology such as transverse displacement sensing.

---

Objective

We combine fields of nano-optics and vectorial fields shaping to achieve a sensitive measurement of deep-subwavelength displacement.

---

Impact

Far field scheme to access nanoscale information has been a fascinating topic for super resolution imaging and ultrahigh precision optical metrology. In this research, with the use of absolute dark region of specific optical beams along with nanostructures, we propose a new far field detection method to measure nanoscale displacement.

By slightly displacing the nanostructure with respect to the absolute dark point or line of the incident beam, the detected signal in the far field can change dramatically. The resolution can be extremely high due to the infinitesimal size of the dark region.

In contrary to conventional methods using short wavelength for the detection, our method requires to use longer wavelength for better results because of the special interactions within the nanostructures. The present method could be implemented in the semiconductor industry to solve the crucial problem of overlay alignment; it would also shed new light on super resolution techniques for localization.

---

Publications

• Information-Efficient Metagrating for Transverse-Position Metrology

  Zheng Xi, Sander Konijnenberg, and H.P. Urbach, Phys. Rev. Applied 14, 014026 (2020)

• Asymmetric Excitation of Surface Plasmon Polaritons via Paired Slot Antennas for Angstrom Displacement Sensing

  Tianyang Zang, Haofeng Zang, Zheng Xi, Jing Du, Han Wang, Yonghua Lu, and Pei Wang, Phys. Rev. Lett. 124, 243901 (2020)

• Retrieving the Size of Deep-Subwavelength Objects via Tunable Optical Spin-Orbit Coupling

  Zheng Xi and H. P. Urbach, Phys. Rev. Lett. 120, 253901 (2018)

• Magnetic Dipole Scattering from Metallic Nanowire for Ultrasensitive Deflection Sensing

  Zheng Xi and H. P. Urbach, Phys. Rev. Lett. 119, 053902 (2017)

• Accurate Feeding of Nanoantenna by Singular Optics for Nanoscale Translational and Rotational Displacement Sensing

  Zheng Xi, Lei Wei, A. J. L. Adam, H. P. Urbach, and Luping Du, Phys. Rev. Lett. 117, 113903 (2016)