Quantum-cascade laser-based nanoscale photoexpansion micro-spectroscopy in mid-infrared and terahertz

We report highly-sensitive photoexpansion micro-spectroscopy using tunable quantum cascade lasers in mid-infrared and terahertz. High sensitivity is obtained by moving laser pulses repetition frequency in resonance with an atomic force microscope cantilever eigenfrequency. 50 nm spatial resolution is demonstrated with a tunable mid-IR QCL.