Propagation and nanofocusing of infrared surface plasmons on tapered transmission lines: Influence of the substrate

• Autores: Sarriugarte, P.; Schnell, M.; Alonso González, P.; Arzubiaga, L.; Golmar, Federico; Casanova, F.; Hueso, L. E.; Hillenbrand, R.
• Año de publicación: 2012
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: INFRARED PLASMONICS; NANOFOCUSING; NEAR-FIELD MICROSCOPY; TRANSMISSION LINES
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We study the propagation of mid-infrared surface plasmons on non-tapered and tapered two-wire transmission lines on Si and CaF 2 substrates, the two materials representing substrates with large and small refractive index, respectively. A comparative numerical study predicts a larger effective wavelength and an increased propagation length (i.e. weaker damping) for the CaF 2 substrate. By near-field microscopy we image the near-field distribution along the transmission lines and experimentally verify surface plasmon propagation. Amplitude- and phase-resolved near-field images of a non-tapered transmission line on CaF 2 reveal a standing wave pattern caused by back-reflection of the surface plasmons at the open-ended transmission line. Calculated and experimental near-field images of tapered transmission lines on Si and CaF 2 demonstrate that for both substrates the mid-IR surface plasmons are compressed when propagating along the taper. Importantly, the nanofocus at the taper apex yields a stronger local field enhancement for the low-refractive index substrate CaF 2. We assign the more efficient nanofocusing on CaF 2 to the weaker damping of the surface plasmons.
Fil: Sarriugarte, P.. No especifíca;
Fil: Schnell, M.. No especifíca;
Fil: Alonso González, P.. No especifíca;
Fil: Arzubiaga, L.. No especifíca;
Fil: Golmar, Federico. Instituto Nacional de Tecnología Industrial; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina
Fil: Casanova, F.. No especifíca;
Fil: Hueso, L. E.. No especifíca;
Fil: Hillenbrand, R.. No especifíca;