Mid-infrared time-domain spectroscopy system with carrier-envelope phase stabilization

We built a mid-infrared time-domain spectroscopy (TDS) system optimized for the 8–12 μm spectral range based on a compact ultrafast Erbium:fiber laser that enables measurements of phase-resolved optical field transients directly in the time domain with high stability and spectral brightness. We achieved long term (>10 h) stability of the TDS signal by using a carrier-envelope-phase locking technique to reduce the timing jitter caused by environmental changes. Time domain measurements of the mid-infrared beam were achieved via electro-optic sampling in a GaSe crystal, using an ultrashort (∼15 fs) output of the fiber laser. Here, we present a full characterization of our TDS system including the dependence of the amplitude and pulse shape of the detected infrared waveforms on the thickness of the GaSe crystals.