Wednesday June 29, 2005
Thursday June 30, 2005

"A New Coherent Infrared Spectrometer Suitable for Near-Field Microscopy "
Mr. Albert Schliesser
Max-Planck-Institut für Biochemie

A novel approach to high-speed mid-infrared spectroscopy is presented. Instead of a relatively weak thermal source it employs coherent broadband infrared radiation generated by nonlinear optical conversion of Ti:Sa femtosecond pulses [1]. Exploiting the comb-like structure of the infrared spectrum generated this way, we are able acquire full amplitude and phase spectra in sub-ms snapshots without any mechanical movement in the setup [2]. By means of a simple modulation technique, we are able to take as much as 1000 spectra/s. While we demonstrate the validity and versatility of this spectrometer in different experiments, we intend to use it in a scanning near-field infrared microscope [3] by focussing the laser-like probe beam on an AFM tip. This method should enable fast, parallel infrared spectroscopy at the nanoscale. [1] C. Fischer and M. W. Sigrist, Mid-IR Difference Frequency Generation,in Solid-State Mid-Infrared Laser Sources, I. T. Sorokina and K. L.Vodopyanov, eds. (Springer, 2003). [2] F. Keilmann, C. Gohle, and R. Holzwarth:Time-domain mid-infrared frequency-comb spectrometer. Optics Letters 29(13), 1542-1544 (2004) [3] F. Keilmann and R. Hillenbrand: Near-field microscopy by elastic light scattering from a tip. Philosophical transactions of the Royal Society of London A 362(1817), 787-805 (2004)