Dresden 2006 – scientific programme

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CPP: Chemische Physik und Polymerphysik

CPP 25: POSTER Electronic Structure and Spectroscopy

CPP 25.9: Poster

Thursday, March 30, 2006, 17:00–19:00, P2

Photothermal Microscopy on Single Quantum Objects — •Romy Raduenz, Achim Gruber, and Frank Cichos — Photonics and Optical Materials, Institute of Physics, Chemnitz University of Technology, 09107 Chemnitz

Single chromophore detection is typically restricted to highly fluorescent entities such as dye molecules or quantum dots. But it fails to access non-fluorescent species. An extension of single chromophore detection to the spectroscopy of non-fluorescent species would thus open a completely new field of studies and analytical possibilities. A technique, which can provide this extension is photothermal detection. Within this technique the conversion of the absorbed photon energy into heat and finally a refractive index change of the local environment is employed to detect single chromophores. This refractive index change is directly proportional to the absorption cross section of the chromophore and therefore allows in principle the measurement of the absorption spectrum. Within our study we present experimental and theoretical results of photothermal confocal microscopy. Our detection scheme is based on the creation of a photothermal lens in the local surrounding of the absorbing species, that is excited by a laser beam. The thermal lens is used to modulate a probe laser beam. The sensitivity of this method is evaluated based on measurements on single gold nanoparticles.