Transverse and Longitudinal Two-photon Photoluminescence Investigation of Single-crystalline Gold Nanoantennas
Wei-Liang Chen1*, Fan-Cheng Lin2, Yu-Yang Lee1, Feng-Chieh Li1, Yu-Ming Chang1, Jer-Shing Huang2,3
1Center for condensed matter sciences, National Taiwan University, Taipei, Taiwan
2Department of Chemistry, National Tsing Hua University, Hsinchu, Taiwan
3Frontier Research Center on Fundamental and Applied Sciences of Matters, National Tsing Hua University, Hsinchu, Taiwan
* presenting author:陳維良,
Plasmonic optical nanoantennas have the unique ability to mediate near- and far-field electromagnetic energy and to enhance light-matter interaction at nanoscale. Resonance excited nanoantenna produces local field enhancements that greatly improves the efficiency of non-linear process, such as two-photon induced photoluminescence (TPPL) and second harmonic generation. Due to the high sensitivity to local field intensity, TPPL has been used to map the field distribution and excitation efficiency of nanoantenna resonant modes. In this study, we used two-photon laser excitation in longitudinal configuration to obtain the longitudinal and transverse TPPL spectra from three sets of nanoantenna of different arm widths and lengths [1]. The transverse TPPL spectra show clear peaks that shifts with the width of the antenna, providing a direct evidence for associating the transverse PL spectra with the transversal plasmonic mode of gold nanoantenna and revealing the depolarization nature of TPPL from gold nanoantennas. The longitudinal TPPL show spectral dips at wavelengths corresponding to anti-bonding dark modes and slight spectral enhancement at wavelengths associated with higher-order bonding bright mode. The wavelengths of the spectral features are in good agreement with the data obtained from numerical simulations and dark-field scattering experiments.

[1] W.-L. Chen, F.-C. Lin, Y.-Y. Lee, F.-C. Li, Y.-M. Chang, and J.-S. Huang, ACS Nano. 8, 9053 (2014).

The authors in NTU acknowledge the financial support from Ministry of Science and Technology (MOST) of Taiwan under Grant No.: NSC102-2119-M-002-015-MY3.

Keywords: nanoantennas, plasmonic resonance, two-photon photoluminescence, dark mode