A flexible, narrowband and broadly tunable mid-IR light source based on shaped sub-10 fs pulses

Summary form only given. Mid-infrared (MIR) spectroscopy is becoming increasingly popular for the study of complex molecules in a number of fields ranging from physics to biology and medicine. While molecular vibrations are usually indirectly probed by Raman-type processes, the direct resonant investigation with IR frequencies ranging from 500-3500 cm
^-1
provides complementary contrast and far better coupling efficiencies. However, due to the limitations of available light sources and efficient detectors in the MIR region, spectroscopies in the visible or near-IR are still the methods of choice. Besides some promising new developments, most of the IR sources applied in laboratories today are based on the output available from difference frequency generation (DFG) stages mixing near-IR light in nonlinear optical crystals.In this contribution we present a novel approach for MIR spectroscopy through the flexible control of the (DFG) process by spectral focusing [1] and fs pulse shaping. Based on the recent developments of this method for CARS microscopy [2, 3] an adapted scheme for controlling the excitation frequencies of the DFG process can be readily implemented. In addition to direct characterization, the method enables to tune the spectral position and spectral pulse width of the MIR output pulse to address specific vibrations for high-resolution spectroscopy or even microscopy applications.