Near-field optics

Micro & Nano Characterization Group

MNC Group

We are studying the local optical properties of dielectric and metallic nanoparticles by near-field optics. The field distribution is measured with our home-built SNOM which uses a small fluorescent nanocrystal as a sensor. The experimental setup is described in Fig. 1. Illumination can be performed in a transmission or a reflection mode at normal or oblique incidence.

We show in Fig. 2 the field distribution measured on an array of gold nanodisks deposited on a glass surface. The experiment reveals the presence of two lobes in good agreement with numerical simulations performed by FDTD (A. Garcia-Martin).

Another example in Fig. 3 shows the near-field measured in a plane just above an isolated gold nanoparticle. Two lobes are visible, aligned with the incident polarization direction.

Our current projects concern the study of coupling effects between metallic nanoparticles, as well as the combination of metallic and dielectric nanostructures.

Fig. 1: Experimental setup.

See for instance:

- Appl. Opt. 42, 6880 (2003).

- J. Appl. Phys. 97, 104322 (2005).

- Opt. Comm. 262, 263 (2006).

- J. Appl. Phys. 110, 044308 (2011).

- Nano Lett. 14, 2079 (2014).

- Appl. Phys. Lett. 111, 251109 (2017).

Fig. 2: Near-field above an array of gold nanodisks: experiment (top) and simulation (bottom). The arrows indicate the incident polarization direction.

Fig. 3: Near-field measured above an isolated gold nanodisk. Two lobes are visible, oriented along the incident polarization direction.