New method for simultaneous characterisation of optical nonlinearity in absorption and scattering from a single gold nanostructure

Tushar Jagadale^1,2*, Shi-Wei Chu^3,4

¹Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
²Technical Physics Division, Bhabha Atomic Research Centre, Mumbai, India
³Department of Physics, National Taiwan University, Taipei, Taiwan
⁴Molecular Imaging Center, National Taiwan University, Taipei, Taiwan

* Presenter:Tushar Jagadale, email:tushar@ntu.edu.tw

Nonlinear nanoplasmonics has promising applications in active components such as lasers and modulators. To quantify material nonlinearity, z-scan is the most widely used method, but it is limited to thin-film measurement, not able to provide single-nanostructure nonlinearity. In this work, a new “x-scan” method, which is based on laser scanning microscopy equipped with forward and backward detectors, is demonstrated to provide simultaneous characterization for nonlinearity of optical absorption and scattering in single nanostructures. Exceptionally large nonlinearity in both plasmonic scattering and absorption are found from a single gold nanostructure, where the underlying mechanism is resonantly enhanced photothermal effect.

Keywords: Single gold nanostructure, nonlinear absorption, absorption cross-section, nonlinear scattering, laser scanning microscopy