Characterizing through-focus pulse front tilt

Pulse front tilt is a spatio-temporal distortion in ultrashort laser pulses characterized by a variation in the arrival time of the pulse across the beam's spatial profile. While often undesirable, pulse front tilt is a key design parameter to optimize the nonlinear frequency conversion process of a Noncolinear Optical Parametric Amplifier (NOPA) to produce broad-bandwidth, tunable ultrashort pulses [1, 2]. Typically, the pulse front tilt is controlled by imaging the exit of a prism onto a nonlinear crystal. We investigate the variation of pulse front tilt near the focus of a lens during pulse propagation, to show that this can be used to optimize pulse front tilt with fewer constraints on the prism design than occur in the imaging geometry. We introduce angular dispersion to 780 nm ultrafast pulses by passing them through a prism and use a single-shot imaging technique to characterize the pulse front tilt [3]. This approach allows us to vary the position of a lens and resolve the evolution of the pulse front tilt during beam propagation. We describe the experimental design and early results.

1. T. Kobayashi and A. Baltuska, Meas. Sci. and Tech. 13 (2002).

2. W. P. Carbery, et al., Rev. Sci. Instrum. 95 (2024).

3. A.K. Sharma, et al., Opt. Express 14 (2006).