A particular research interest of the CETAL-PW group is the development of high-power laser systems, addressing themes such as controlling and diagnosing complex beam pulses delivered at the interaction, as well as developing new methods to overcome the current technological limitations in terms of peak irradiance.
One path was initiated by Professor Razvan Dabu in 2015 in close collaboration with a team led by Gerard Mourou, involving the high-power laser facilities of TEWALAS and CETAL-PW for preliminary tests and implementation of a method for shortening the already amplified ultrashort pulse duration towards a few cycles by further temporal re-compression of the already amplified ultrashort laser pulses following nonlinear interaction with thin plastic films. This concept was entitled: Thin Film Compressor (TFC). Thus, feasibility studies of the TFC concept were implemented at the TEWALAS facility by constructing an experimental setup and identifying procedures for testing and diagnosing the interaction of films with laser pulses of peak power greater than 1 TW/cm² in vacuum conditions. Further, the experiments continued at the CETAL-PW facility and revealed encouraging results suggesting that the parameters of films with thicknesses up to 0.5 mm interacting with collimated laser beams with intensity of approximately 1.5 TW/cm2 are a good combination to produce a broadening of the spectrum while maintaining a low energy loss [Figure 1]. Also here, a prototype of a temporal pulse compressor based on 25 mm diameter chirped mirrors was designed and implemented [Figure 2], which was used to experimentally demonstrate in a first stage a reduction of the experimentally measured pulse duration from 45 to 29 femtoseconds. The obtained results were published in the paper “100 J-level pulse compression for peak power enhancement” (Quantum Electronics 2017). The experiments were subsequently resumed by the same team at the LASERIX facility in France, within a project funded by the European LASERLAB program, where the preliminary results from CETAL were successfully reproduced and several types of plastic films were tested, with different thicknesses and number of interactions, further showing that following the implementation of this new temporal compression method, the beam quality – focu sability can be maintained [Figure 3] and the results of these studies were published in two papers published in international journals with ISI impact factor: “Focusability of laser pulses at petawatt transport intensities in thin-film compression” (2019, Journal of the Optical Society of America B), respectively "Compressing High Energy Lasers through Optical Polymer Films" (2022, Photonics).

 

                         

 

 

In recent decades, substantial progress has been made in the field of ultra-high intensity laser physics, enabling the exploration of matter and vacuum in extreme electric and magnetic fields. Central to this advancement is the development of multi-petawatt femtosecond laser systems, to reach peak intensities of 10²³ W/cm² and beyond. However, these ambitions are constrained by the physical limits of optical components, especially when scaling up power using traditional laser architectures.
To overcome these barriers, Coherent Beam Combination (CBC) has emerged as a key technique, enabling the superposition of multiple laser beams to act as a single, higher-power beam.
Another path towards overcoming these technological barriers to increase further peak irradiance is to develop a technique to enable the superposition of multiple laser beams to act as a single, higher-power beam, the Coherent Beam Combination (CBC). While it has been demonstrated in various configurations, extending this method to low repetition rate, petawatt-class femtosecond Ti: sapphire lasers remains a significant technical challenge due to issues such as phase stability, beam synchronization, and optical path fluctuations in dynamic, noise-prone environments.
The Cetal-PW team proposes a novel hybrid control method, combining nonlinear optical diagnostics and high-precision interferometry, to synchronize and coherently combine two amplified femtosecond laser beams.