Wavelength-Dependent Wavefront Produced and Controlled in Optical Parametric Chirped-Pulse Amplification

It is generally impossible to maintain tight focusing over a long distance because of diffraction; this so-called Rayleigh's curse may be broken for a femtosecond laser if the wavefront curvature varies with laser wavelength. This paper reports on a nonlinear technique to produce a wavelength-dependent wavefront. We reveal a wavelength-dependent wavefront mechanism that is induced in optical parametric chirped-pulse amplification (OPCPA) where the crystal effect of group-velocity mismatch (GVM) dominates. Both analytical and numerical investigations show that the sign of the produced wavefront can be changed by GVM, and the magnitude can be enhanced by multistage OPCPA. The results suggest that the Rayleigh range at a fixed beam waist size can be significantly increased by the OPCPA-induced wavelength-dependent wavefront.

Automated summary

This paper introduces a nonlinear technique to produce wavelength-dependent wavefront curvature, which can break Rayleigh's curse for a femtosecond laser. By utilizing optical parametric chirped-pulse amplification, the mechanism of wavelength-dependent wavefront is induced, enabling the change of focal spot size and increased Rayleigh range.