TY - JOUR

T1 - Generating Ultrabroadband Deep-UV Radiation and Sub-10 nm Gap by Hybrid-Morphology Gold Antennas

AU - Shi, Liping

AU - Cardoso de Andrade, José Ricardo

AU - Tajalli Seifi, Ayhan

AU - Geng, Jiao

AU - Yi, Juemin

AU - Heidenblut, Torsten

AU - Segerink, Frans B.

AU - Babushkin, Ihar

AU - Kholodtsova, Maria

AU - Merdji, Hamed

AU - Bastiaens, Bert

AU - Morgner, Uwe

AU - Kovacev, Milutin

N1 - The authors thank funding supports from Deutsche Forschungsgemeinschaft (DFG) (KO 3798/4-1) and from German Research Foundation under Germany’s Excellence Strategy EXC-2123 and Germany’s Excellence Strategy within the Cluster of Excellence PhoenixD (EXC 2122, Project ID 390833453), Lower Saxony through “Quanten und Nanometrologie” (QUANOMET, Project Nanophotonik). H.M. acknowledges support from the PETACom FET Open H2020, support from the French ministry of research through the ANR grants 2014 “IPEX”, 2017 “PACHA”, the DGA RAPID grant “SWIM”, the LABEX “PALM” (ANR-10-LABX-0039-PALM) through he grants “Plasmon-X”, “STAMPS”, and “HILAC”. We acknowledge financial support from the French ASTRE program through the “NanoLight” grant.

PY - 2019/6/17

Y1 - 2019/6/17

N2 - We experimentally investigate the interaction between hybrid-morphology gold optical antennas and a few-cycle Ti:sapphire laser up to ablative intensities, demonstrating rich nonlinear plasmonic effects and promising applications in coherent frequency upconversion and nanofabrication technology. The two-dimensional array of hybrid antennas consists of elliptical apertures combined with bowties in its minor axis. The plasmonic resonance frequency of the bowties is red-shifted with respect to the laser central frequency and thus mainly enhances the third harmonic spectrum at long wavelengths. The gold film between two neighboring elliptical apertures forms an hourglass-shaped structure, which acts as a "plasmonic lens" and thus strongly reinforces surface currents into a small area. This enhanced surface current produces a rotating magnetic field that deeply penetrates into the substrate. At resonant frequency, the magnetic field is further intensified by the bowties. The resonant frequency of the hourglass is blueshifted with respect to the laser central frequency. Consequently, it spectacularly extends the third harmonic spectrum toward short wavelengths. The resultant third harmonic signal ranges from 230 to 300 nm, much broader than the emission from a sapphire crystal. In addition, the concentration of surface current within the neck of the hourglass antenna results in a structural modification through laser ablation, producing sub-10 nm sharp metallic gaps. Moreover, after laser illumination the optical field hotspots are imprinted around the antennas, allowing us to confirm the subwavelength enhancement of the electric near-field intensity.

AB - We experimentally investigate the interaction between hybrid-morphology gold optical antennas and a few-cycle Ti:sapphire laser up to ablative intensities, demonstrating rich nonlinear plasmonic effects and promising applications in coherent frequency upconversion and nanofabrication technology. The two-dimensional array of hybrid antennas consists of elliptical apertures combined with bowties in its minor axis. The plasmonic resonance frequency of the bowties is red-shifted with respect to the laser central frequency and thus mainly enhances the third harmonic spectrum at long wavelengths. The gold film between two neighboring elliptical apertures forms an hourglass-shaped structure, which acts as a "plasmonic lens" and thus strongly reinforces surface currents into a small area. This enhanced surface current produces a rotating magnetic field that deeply penetrates into the substrate. At resonant frequency, the magnetic field is further intensified by the bowties. The resonant frequency of the hourglass is blueshifted with respect to the laser central frequency. Consequently, it spectacularly extends the third harmonic spectrum toward short wavelengths. The resultant third harmonic signal ranges from 230 to 300 nm, much broader than the emission from a sapphire crystal. In addition, the concentration of surface current within the neck of the hourglass antenna results in a structural modification through laser ablation, producing sub-10 nm sharp metallic gaps. Moreover, after laser illumination the optical field hotspots are imprinted around the antennas, allowing us to confirm the subwavelength enhancement of the electric near-field intensity.

KW - broadband deep-ultraviolet

KW - laser ablation

KW - nanoscale gaps

KW - near-field mapping

KW - Nonlinear plasmonics

UR - http://www.scopus.com/inward/record.url?scp=85068112397&partnerID=8YFLogxK

U2 - 10.1021/acs.nanolett.9b02100

DO - 10.1021/acs.nanolett.9b02100

M3 - Article

C2 - 31244236

AN - SCOPUS:85068112397

VL - 19

SP - 4779

EP - 4786

JO - Nano Letters

JF - Nano Letters

SN - 1530-6984

IS - 7

ER -