期刊
NANO LETTERS
卷 19, 期 4, 页码 2549-2554出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.nanolett.9b00304
关键词
surface phonon polariton; cavity; near-field spectroscopy; phase change materials
类别
资金
- DFG (German Science Foundation) within the collaborative research center Nanoswitches [SFB 917]
- Ministry of Innovation, Science Research and Technology of the German State of North Rhine-Westphalia
- German Federal Ministry of Education and Research under Photonics Research Germany program [13N14151]
- DFG through the Heisenberg Fellowship [CH 407/7-2]
Mid-infrared (MIR) photonics demands highly confined optical fields to obtain efficient interaction between long-wavelength light and nanomaterials. Surface polaritons excited on polar semiconductor and metallic material interfaces exhibit near-fields localized on subwavelength scales. However, realizing a stronger field concentration in a cavity with a high quality (Q) factor and a small mode volume is still challenging in the MIR region. This study reports MIR field concentration of surface phonon polaritons (SPhPs) using planar circular cavities with a high Q factor of similar to 150. The cavities are fabricated on a thin film of the phase change material Ge3Sb2Te6 (GST) deposited on a silicon carbide (SiC) substrate. Scattering-type scanning near-field optical microscopy visualizes the near-field distribution on the samples and confirms directly that the SPhP field is strongly concentrated at the center of the centrosymmetric cavities. The smallest concentrated field size is 220 nm in diameter which corresponds to 1/50 of the wavelength of the incident light that is far below the diffraction limit. The thin GST film enhances the SPhP confinement, and it is used to switch the confinement off by tuning the cavity resonance induced by the phase change from the amorphous to the crystalline phase. This subwavelength and switchable field concentration within a high-Q polariton cavity has the potential to greatly enhance the light-matter interaction for molecular sensing and emission enhancement in MIR systems.
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