Title: Effects of Phase-Matching on High Harmonic Generation from Aligned N2

Brett A. Sickmiller and R.R. Jones

Abstract:

We have used two time-delayed laser pulses to examine high harmonic generation from transiently aligned, room temperature N2 molecules in a hollow-core waveguide. The extended interaction length in the waveguide allows us to identify alignment-dependent propagation effects which mask the single molecule response. In particular, we observe a reversal in the harmonic efficiency from parallel to perpendicular alignment. This reversal depends on laser intensity and harmonic order. Simulations indicate that it can be attributed to the alignment-dependence of the tunneling ionization rate and the concomitant modification of the phase-matching conditions due to the changes in the free-electron density in the fiber.

Status: Physical Review A 80, 031802(R) (2009)