Laser-induced damage growth of fused silica optics near growth threshold at 351 nm.

Laser-induced damage growth on the exit surface of fused silica optics triggered by nanosecond pulses at 351 nm is widely described with exponential dynamics. In this Letter, a particular experimental setup allowed us to study damage growth with a large beam and fluences near damage growth threshold for a high number of shots. This allowed us to observe and characterize a regime with a slow and linear growth dynamic not documented in the literature and yet fundamental for the operation of high-power laser installations.

Linear-to-circular polarization conversion with full-silica meta-optics to reduce nonlinear effects in high-energy lasers.

High-energy lasers have benefited from intense efforts to bring light-matter interactions to new standards and to achieve laser fusion ignition. One of the main issues to further increasing laser energy is the resistance of optical materials to high laser fluences, in particular at the final stage of the laser beamline where nonlinear Kerr effects can occur in optical materials and provoke laser filamentation. One promising way to mitigate this process is to reduce the nonlinear susceptibility of the material by switching the polarization from a linear to a circular state. Here, we report a significant reduction in the laser filamentation effect on glass by using a full-silica metamaterial waveplateable to switch the linear-to-circular polarization of high fluence laser beams. This result is achieved through the use of a large size full-silica meta-optics exhibiting nominal polarization conversion associated with an excellent transmission efficiency and wavefront quality, as well as a high laser damage resistance.

High-gain fiber, optical-parametric, chirped-pulse amplification of femtosecond pulses at 1 µm.

Fiber-based optical-parametric chirped-pulse amplification is reported at 1µm in a microstructured fiber in the femtosecond regime. The signal has been highly stretched by an Öffner triplet and then amplified with an all-fiber, pulsed-pump, fiber optical-parametric amplifier. More than 30dB gain has been achieved over 8.3nm, and the amplified signal has been recompressed.

Nonsinusoidal phase modulations for high-power laser performance control: stimulated Brillouin scattering and FM-to-AM conversion.

High-power lasers, such as the Laser MegaJoule (LMJ), have to be phase modulated to avoid stimulated Brillouin scattering (SBS) that may strongly damage optics at the end of the laser chain. Current spectral broadening on LMJ is performed with a sinusoidal phase modulation. This pure sinusoidal phase modulation leads to inhomogeneous spectral power densities (SPD). Thus, for a same SBS power threshold, the sinusoidal phase-modulated spectrum has to be larger than the equivalent ideal SPD with isoenergetic peaks. We present in this paper a technique to generate energy-balanced Dirac peaks spectra thanks to nonsinusoidal phase modulations. Thus, we can build a narrower spectrum with a nonsinusoidal phase modulation that has the same SBS threshold as a sinusoidal phase modulation, and we show that FM-to-AM conversion can be strongly reduced, which is of great interest for LMJ laser performance, with reductions up to 40%.

Demonstration of a true single-shot 100 GHz-bandwidth optical oscilloscope at 1053-1064 nm.

We demonstrate an innovating design to validate and to optimize the real-time performance of an all-optical oscilloscope at 1053-1064 nm. A unique broadband pulse is generated by means of frequency beats and of proper optical-shaping, which helps us to evidence a signal bandwidth of 100 GHz and a dynamics range in excess of 25 dB. Gain-narrowing and dispersion effects due to the replication of the input pulse are shown to be the first limitations in the broadband capabilities.