Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - NonlinearMeta (Controlling optical nonlinearity with plasmonic metamaterials)

Teaser

The overall objective of the project ‘NonlinearMeta’ by Dr. Shumei Chen is to develop ultra-compact, high-efficient, and dynamically controllable nonlinear photonic metasurface to open up exciting opportunities and new applications in the areas of light information...

Summary

The overall objective of the project ‘NonlinearMeta’ by Dr. Shumei Chen is to develop ultra-compact, high-efficient, and dynamically controllable nonlinear photonic metasurface to open up exciting opportunities and new applications in the areas of light information processing at nanoscale interfaces. Recently, nonlinear photonic metasurfaces consisting of spatially varying nanostructures have attracted great interest in the fields of frequency conversion, bio-sensing, optical communication and quantum optics. However, one of the key problem that limits the application of nonlinear photonic metasurface is its extremely low conversion efficiency. In this project, Dr. Chen has proposed several concepts for enhancing the conversion efficiency of various nonlinear optical processes by introducing strong light localization in both silicon photonic metasurfaces and multi-layer thin film based photonic devices. Dr. Chen also investigated the giant circular dichroism effect in second harmonic generation from achiral metasurface and the rotational Doppler effect from rotating metasurfaces with rotational symmetries. Moreover, based on the concept of nonlinear geometric Berry phase, Dr. Chen has developed several plasmonic metasurface to study the spin-orbital interactions in both second harmonic generation and four wave mixing process. It is expected that such nonlinear photonic metasurface devices can greatly enrich the functionalities of nonlinear photonic crystals and lead to a promising way of developing on-chip nonlinear optical sources and sensors.
The Project “NonlinearMeta” has been successfully provided novel routes for controlling the amplitude and phase of second and third harmonic generation processes on nonlinear photonic metasurfaces, which is of potential importance for developing novel information processing techniques of light. The project has fully achieved its objectives and technical goals. The project has delivered nonlinear photonic metasurface devices with improved optical efficiencies and multi-functionalities to both the academic and industrial communities. The science and technology on nonlinear photonic metasurfaces, electrically controlled harmonic generation, and giant nonlinear circular dichroism could be transferred to high-tech companies in optoelectronic industry, and finally contribute to the national economic success.

Work performed

There are four objectives proposed in the project “NonlinearMeta”. All these four objectives have been achieved by the following four tasks.
Task 1 was the demonstration of complementary silicon metasurface for high efficient third-harmonic generation. Here we proposed a concept for enhancing the efficiency of third harmonic generation in a complementary silicon nonlinear metasurface, consisting of nanoapertures of cross-like shape in the silicon film. The efficiency enhancement is based on a multipolar interference between the magnetic dipole and electric quadrupole, resulting in significant near-field enhancement. The measured efficiency of third harmonic generation from the silicon metasurface is ~953 times higher than that from the planar silicon film of the same thickness. The mechanism of nonlinear optical enhancement is verified through theoretical calculations. Multipolar enhanced third harmonic generation in complementary dielectric nanostructure opens up a new route for developing high-efficiency nonlinear metasurfaces. The results from this task had been published in ACS Photonics (S. Chen et. Al. ACS Photonics 5, 1671 (2018))
Task 2 was the demonstration of giant tuneability of Electric Field Induced Second Harmonic (EFISH) signal from a subwavelength thick polymer film sandwiched by a transparent electrode and a metallic mirror. By exploiting band-edge enhanced third-order nonlinear susceptibility from the organic conjugated polymer, we successfully demonstrate a gigantic EFISH effect with modulation ratio up to 422%/Volt at pumping wavelength of 840 nm. The band-edge enhanced EFISH opens new avenues for modulating the intensity of second harmonic generation signals, and for controlling nonlinear electro-optic interaction in nanophotonic devices. The results from this task had been published in Light: Science & Applications (S. Chen et. Light: Science & Applications 8, 17 (2019).)
Task 3 was the investigation of strong circular dichroism effect in second harmonic generation processes by utilizing lattice surface modes on the plasmonic metasurface consisting of split ring resonator meta-atoms. We showed that the optical chirality can be further enhanced using nonlinear optical process on an ultrathin plasmonic metasurface. Specifically, we theoretically and experimentally demonstrated the strong circular dichroism for second harmonic generation on plasmonic metasurfaces consisting of split ring resonator meta-atoms. The giant circular dichroism is attributed to the lattice surface modes at fundamental wavelength. Our findings may open new routes to design novel nonlinear optical devices with strong optical chirality.
Task 4 was the measurement of the Doppler shift of SHG from rotating c-cut quartz crystal with C3 crystal symmetry and rotating metallic metasurface with C3 rotational symmetry. In this task, Dr. Chen finished the theoretical analysis and had found that when the circularly polarized light passes through a rotating half waveplate, the change of angular momentum of light will introduce a Doppler frequency shift.
During this project, Dr. Chen had published totally five papers on high impact journal including a review article on nonlinear metasurface and had been invited to give two invited talks and a poster in international conferences.

Final results

The opportunities offered by this Fellowship is very important in Dr. Shumei Chen’s academic career. During the two years’ period of the project, Dr. Chen had successfully become an internationally-leading young researcher in areas of nonlinear optics and photonic metamaterials. She was awarded the “Young Experts Program” under the “1000-Talent Program of China” in Mar 2019 with a total amount of 2.0M RMB research funding provided by the government of China to support her further research in Nonlinear Nanophotonics area. Dr. Chen will begin to work in the School of Science, Harbin Institute of Technology, Shenzhen, China as Professor from April 2019.
The Europe society has benefit from novel concept of nonlinear optical metasurfaces proposed in this project. The results from the proposed nonlinear optical metamaterial not only provide ultra-compact nonlinear optical sources but also have important applications for on-chip light information processing. The science and technology on nonlinear metasurface crystals, electrically controlled harmonic generation, metasurface interferometer and giant nonlinear circular dichroism could be transferred to high-tech companies in optoelectronic industry, and finally contribute to the national economic success. While working in Prof. Shuang Zhang’s group in University of Birmingham, Dr. Chen has also build her international network and coordinate the international collaborations between groups from Germany (Prof. Thomas Zentgraf at University of Paderborn) and UK (Prof. A. Zayats at King’s Collage London). Dr. Chen will continue the long term collaborations with these groups through joint research funding application, joint research projects and student exchanging program after she goes back to China.

Website & more info

More info: https://scholar.google.co.uk/citations.