Damage growth characteristics on the exit surface of fused silica by the low-temporal coherence light irradiation.

The growth of fused silica surface damage poses a high risk in operating high-power laser devices, with complex physical mechanisms related not only to the wavelength, pulse width, fluence of incident pulse lasers, but also to initial damage size and material properties. With low-temporal coherence light (LTCL) increasingly applied in high-power laser-driven inertial confinement fusion (ICF), LTCL-induced damage growth has become a bottleneck limiting output power improvements. This paper analyzes LTCL damage growth characteristics and mechanisms on fused silica surfaces, obtaining its damage growth coefficient and threshold.

Laser cooling by over 7 K in Yb-doped ZBLAN fibers with high-power pumping at atmospheric pressure.

Anti-Stokes fluorescence (ASF) cooling has been demonstrated to be a viable method for balancing the waste heat produced in gain materials. In addition, radiation-balanced fiber lasers and amplifiers at atmospheric pressure have recently been developed. Here, we evaluate the cooling characteristics in a long section of a Yb-doped ZBLAN fiber with high pump power.

Full-aperture random polarization smoothing for a low-coherence laser facility.

Two new random polarization smoothing methods using full-aperture elements are proposed on low-coherence lasers, one using birefringent wedge and one using flat birefringent plate. By designing the crystal axis direction and wedge angle of the birefringent plates, the methods can selectively introduce time delay and spatial displacement, so as to obtain fast random evolution of transient polarization by utilizing low spatiotemporal coherence of the laser focal field. Both methods avoid the near field discontinuity and can be used under high fluence.

Fast time-evolving random polarization beam smoothing for laser-driven inertial confinement fusion.

We propose a random polarization smoothing method for low-coherence laser to obtain focal spot with random polarization that evolves rapidly in sub-picosecond timescales. Random polarization smoothing is realized by a half-aperture wave plate with sufficient thickness. The degree of polarization and polarization evolution of the focal spot are studied theoretically.

High-power, low-coherence laser driver facility.

We report the first (to the best of our knowledge) high-power, low-coherence Nd:glass laser delivering kilojoule pulses with a coherent time of 249 fs and a bandwidth of 13 nm, achieving the 63%-efficiency second-harmonic conversion of the large-aperture low-coherence pulse and good beam smoothing effect. It provides a new type of laser driver for laser plasma interaction and high energy density physics research.

Experiment and theory of beam smoothing using induced spatial incoherence with a lens array.

The smoothing effect of induced spatial incoherence combined with a lens array on a large-bandwidth and short-coherence-time laser is reported. A theoretical model based on statistical optics is developed to describe the spatial and temporal characteristics of the focal spot. Theoretical simulation is consistent with the experimental results.

High-efficiency second-harmonic generation of low-temporal-coherent light pulse.

The nonlinear frequency conversion of low-temporal-coherent light holds a variety of applications and has attracted considerable interest. However, its physical mechanism remains relatively unexplored, and the conversion efficiency and bandwidth are extremely insufficient. Here, considering the instantaneous broadband characteristics, we establish a model of second-harmonic generation (SHG) of a low-temporal-coherent pulse and reveal its differences from the coherent conditions.

Beam smoothing by a diffraction-weakened lens array combining with induced spatial incoherence.

The smoothing scheme combining a diffraction-weakened lens array with the induced spatial incoherence method is proposed and demonstrated to be an efficient smoothing scheme for broadband laser systems. In our simulation, the RMS illumination nonuniformity of the target spot is reduced to 2% after sufficient smoothing time. The temporal characteristics and spatial power spectral density of the scheme are theoretically analyzed.

Investigation of phase effects of coherent beam combining for large-aperture ultrashort ultrahigh intensity laser systems.

Large-aperture ultrashort ultrahigh intensity laser systems are able to achieve unprecedented super-high peak power. However, output power from a single laser channel is not high enough for some important applications and it is difficult to improve output power from a single laser channel significantly in the near future. Coherent beam combining is a promising method which combines many laser channels to obtain much higher peak power than a single channel.