Research themes

• Light-matter interactions on the nanoscale
• Nonlinear nano-optics
• Surface plasmon nanophotonics

The development of scanning near-field optical microscopy (SNOM) has opened the possibility for studying numerous optical phenomena with resolution well below the diffraction limit. In conventional (far-field) spectroscopy one can measure only an average signal originating from the relatively large surface area determined by the illuminating spot, without exact knowledge of surface morphology. The local field intensity can vary by several orders of magnitude on a scale less than half a wavelength along a surface. For this reason, far-field investigations of optical properties in many cases do not result in an understanding of the underlying microscopic physics, especially in nonlinear spectroscopy where optical response depends on the driving field in a nonlinear manner. The combination of near-field microscopy with spectroscopic techniques has enormous potential for optical probing and characterisation of materials, surfaces, and thin films locally on the nanoscale.

Nonlinear spectroscopy

Second-harmonic generation (SHG) is extremely sensitive to surface structure down to atomic scale. In this respect SHG is an ideal tool for investigating the optical properties related to morphology of dielectric, semiconductor, and metal surfaces. Since SHG is sensitive to any asymmetry of material including surface magnetic and electric polarisation, near-field microscopy of second-harmonic generation can be used to characterise ferromagnetic and ferroelectric materials and image magnetic and electric domains as well as domain walls. 

Research areas

• near-field second-harmonic generation for materials characterisation on the nanoscale
• electromagnetic field enhancement and confinement
• novel nanostructured photonic materials
• all-optical integrated circuits for classical and quantum information processing

• local SHG from ferromagnetic and ferroelectric materials and domains imaging
• linear and nonlinear spectroscopy of photonic and polaritonic crystals
• active plasmonics
• high-resolution optical imaging without SNOM
• plasmonic nanowires
• planar chirality
• nanoscopic light sources and apertureless second-harmonic SNOM

We maintain close collaborative links with the research groups working on the front edge of near-field nano-optics, among them University of Southampton and UCL (UK), Universities of North Florida (USA), University of Bourgogne, Dijon, and Paris XIII (France), Laser Zentrum Hannover e.V. (Germany) and many others within the EU and UK research networks.

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