Fumika Isono^{1、2、*}, Jeroen van Tilborg^{1}, Samuel K. Barber^{1}, Joseph Natal^{1、2}, Curtis Berger^{1、2}, Hai-En Tsai^{1}, Tobias Ostermayr^{1}, Anthony Gonsalves^{1}, Cameron Geddes^{1}, and Eric Esarey^{1}

Author Affiliations
^{1}Lawrence Berkeley National Laboratory, Berkeley, CA, USA^{2}University of California, Berkeley, CA, USAshow less

Abstract

Controlling the delivery of multi-terawatt and petawatt laser pulses to final focus, both in position and angle, is critical to many laser applications such as optical guiding, laser–plasma acceleration, and laser-produced secondary radiation. We present an online, non-destructive laser diagnostic, capable of measuring the transverse position and pointing angle at focus. The diagnostic is based on a unique double-surface-coated wedged-mirror design for the final steering optic in the laser line, producing a witness beam highly correlated with the main beam. By propagating low-power kilohertz pulses to focus, we observed spectra of focus position and pointing angle fluctuations dominated by frequencies below 70 Hz. The setup was also used to characterize the excellent position and pointing angle correlation of the 1 Hz high-power laser pulses to this low-power kilohertz pulse train, opening a promising path to fast non-perturbative feedback concepts even on few-hertz-class high-power laser systems.\begin{align}\rho =\frac{\operatorname{cov}\left({c}_{n1},{c}_{n2}\right)}{\sigma_{c1}{\sigma}_{c2}},\end{align} | ((1)) |

\begin{align}S(f)=\frac{\Delta {t}^2}{T}{\left|I(f)\right|}^2=\frac{\Delta {t}^2}{T}{\left|\sum \limits_{n=1}^N{c}_n{e}^{-2 i\pi fn\Delta t}\right|}^2,\end{align} | ((2)) |

\begin{align}\sigma =\sqrt{\int_0^{\infty }2\ S(f) \hbox{d}f}.\end{align} | ((3)) |

\begin{align}{\sigma}^{\ast}\left({f}_{\mathrm{cutoff}}\right)=\sqrt{\int_{f_{\mathrm{cutoff}}}^{\infty }2\ S(f) \hbox{d}f}.\end{align} | ((4)) |