Frequency Comb Velocity-Modulation Spectroscopy

We have demonstrated a new technique that provides massively parallel comb spectroscopy sensitive specifically to ions through the combination of cavity-enhanced direct frequency comb spectroscopy with velocity-modulation spectroscopy. Using this novel system, we have measured electronic transitions of HfF+ and achieved a fractional absorption sensitivity of 3 x 10(-7) recorded over 1500 simultaneous channels spanning 150 cm(-1) around 800 nm with an absolute frequency accuracy of 30 MHz (0.001 cm(-1)). A fully sampled spectrum consisting of interleaved measurements is acquired in 30 min.