Electro-optic sampling (EOS) has established itself as one of the main techniques for coherent THz spectroscopy. In recent years, EOS has been pushed towards recording infrared or even optical waveforms, opening up new possibilities for spectroscopy in these spectral regions. In this contribution, we demonstrate the potential of electric-field-resolved detection via EOS for broadband, mid-infrared molecular vibrational spectroscopy. We show that field-resolved spectroscopy can achieve detection sensitivities orders of magnitude higher than state-of-the art Fourier-transform infrared spectroscopy. This is achieved by high-quantum-efficiency non-linear temporal “piercing” and, therefore, isolation of the molecular signal from the orders-of-magnitude stronger impulsive excitation. Thereby limitations due to detector dynamic range and source excitation noise can be avoided. This promises a new level of molecular sensitivity and molecular coverage for probing complex biological samples.
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