ILOOP

ILOOP targets the optimization of propagation characteristics of femtosecond laser by the use of high damage threshold femtosecond mirrors and multi-conjugate adaptive optics linked to a phase diversity wavefront sensor. This optimisation targets applications such as generation of multi-filaments under controlled beam conditions and target glare. It fits into the theme 5 of this tender and more particularly in the theme 2.5.2. This optimization is carried out along two axes and more precisely in the theme 2.5.3: Development of mirrors with a high damage threshold, and development of a new generation of adaptive optics (called multi-conjugate) to control in spatial phase and amplitude of the beam. Applications of the developments made in this project relate to both civilian and military sector. Intense laser sources have known many developments since the early 90s, this in order to increase the peak power. Significant progress was also made through average power higher and higher. Developments continue especially for systems such as the Apollon-ILE program in France. The various pillars of European ELI programs in the Czech Republic, Romania and Hungary are under construction and are designed for peak power of 10 PW with pulse durations of 15 fs and an energy of 150 joules. These lasers are at the state of the art, but many other less powerful systems are now under construction by the institutions themselves or purchased from companies such as Thales and Amplitude Technologies. A requirement common to all these systems is to reach highest intensity in the experimental plane, with applications both civilian and military side. To meet these requirements, these intense laser sources require optical components of high quality (reflectivity, flatness and damage threshold) and also of large dimension. The spatial beam quality, essential to achieve the desired flux densities, is itself improved by the use of adaptive optics. The analysis of the state of the art on these two elements shows that substantial improvements in laser performance can be considered. The project will focus on: - Developing reflective mirrors that will be of high damage threshold to transport the recompressed pulses while reducing the dimensions of the beam. The partner for this development is SAGEM-REOSC. For obvious strategic reasons it is important to have a French supplier of mirrors compatible with femtosecond pulses. These skills are sorely lacking in France today, forcing the French leaders in the field, Amplitude Technologies and Thales to purchase abroad. As part of this project SAGEM-REOSC intends to develop its know-how to position itself as a French supplier of this strategic market. - Integrating in a femtosecond laser, multi-conjugated adaptive optics coupled to a new wavefront sensor based on the phase diversity to control both spatial amplitude and phase . The partner for the implementation of this loop is the team High Angular Resolution (HRA) of the Department of Theoretical and Applied Optics (DOTA) ONERA, which has a recognized expertise in the design and implementation of adaptive optics. The use of two deformable mirrors placed in two planes allow proper shaping of the beam dynamics in order to optimize its propagation properties (annular or top-hat) and also for focusing.