On the generation of superluminal or subluminal orbital angular momentum femtosecond laser pulse *

The superluminal electromagnetic radiation is one of intriguing concepts after Einstein’s relativity theory [1-2]. Recently, the superluminal behavior of a high-power ultrashort laser pulse is of great interest [3-5]. In this presentation, analytic expression for an electric field describing a superluminal/subluminal femtosecond(fs) laser focus has been presented for a fs laser pulse with an orbital angular momentum (OAM). The analytic expression for a spatio-temporal field distribution is obtained through a diffraction integral plugged by a time-dependent longitudinal chromatic aberration (LCA) under the paraxial approximation and its Fourier transformation. It shows that the speed and the pulse duration of a laser focus depends on the group delay dispersion and a chromaticity parameter determined by the LCA of a focusing optic. The expression is applied to show the generation of a several fs superluminal OAM laser focus.

References

1. V. L. Ginzburg, Theoretical Physics and Astrophysics (Pergamon Press, 1979).

2. B. M. Bolotovski and A. V. Serov, Phys.-Usp. 48, 903 (2005).

3. A. Sainte-Marie, O. Gobert, and F. Quere, Optica 4, 1298 (2017).

4. D. H. Froula, et al., Nat. Photon. 12, 262–265 (2018).

5. J. P. Palastro, et al., Phys. Rev. A 97, 033835 (2018).