Shaping of ultraviolet femtosecond laser pulses by Fourier domain harmonic generation.

E Hertz,O Faucher,P Béjot,B Lavorel,G Karras,F Billard

doi:10.1364/oe.24.027702

Abstract

We present a method to finely tailor ultraviolet femtosecond laser pulses using a pulse shaper with ability in the infrared/visible spectral range. We have developed to that end a frequency doubling module in which the up-conversion mechanism is carried out in the Fourier plane of a 4 f -line. The pulse shaper is used to imprint a spectral phase and/or amplitude onto the fundamental pulse. The shaped pulse is then frequency doubled through the module which transfers the applied spectral shaping to the second harmonic field in a predictable manner. The relevance of the method is demonstrated by synthesizing and characterizing shaped pulses at a central wavelength of 400 nm. The results demonstrate a full control over the spectral phase and amplitude of the harmonic field. The experimental setup is simple and features interesting prospects for the polarization shaping of ultraviolet pulses and the production of shaped ultraviolet pulses requested for the seeding of free-electron lasers.

Highlights

Programmable temporal shaping of femtosecond pulses has resulted in major advances in a wide array of physics with plenty of breakthrough applications for controlling atoms or molecules, pulse compression, and nonlinear microscopy to name a few. [1] All techniques enabling the generation of sophisticated optical waveforms operate in the frequency domain
We have reported on the shaping of femtosecond UV pulses using a method converting waveforms from near infrared (NIR) to UV
The method is based on the second harmonic generation (SHG) of tailored pulses synthesized in the NIR/VIS spectral range

Summary

Introduction

Programmable temporal shaping of femtosecond (fs) pulses has resulted in major advances in a wide array of physics with plenty of breakthrough applications for controlling atoms or molecules, pulse compression, and nonlinear microscopy to name a few. [1] All techniques enabling the generation of sophisticated optical waveforms operate in the frequency domain. [2] Conventional pulse shapers have been predominantly developed in the visible (VIS) and near infrared (NIR) spectral domain because of the limited transparency range of implemented materials. This property was in addition compatible with the most widely used fs laser source, namely the Ti:sapphire operating in the near-infrared. Most of investigations on this topic have been based on multiphoton excitation with IR fields which excludes de facto the possibility of weak field excitation This strategy prevents a control over the phase of the excitation without modifying the transition probability which sometimes implies the use of tricky normalization procedures. The optimal pulses for the excitation of the photocathode must have flat-top shape of few picosecond (ps) duration in the UV range. [3,4] another potential application of UV shaping is the “upcoming” field of attochemistry, where shaped UV pulses could be used in order to control the fate of the excited cationic states produced by the extreme ultraviolet pulses. [5]

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