Beam breakup integral measurement on high-power laser chains

Mitigation of the small-scale self-focusing effect by a rotating laser beam in a high-power laser

Intense lasers tend to produce nonlinear effects during propagating through the nonlinear media, which greatly limits the output power and beam quality of lasers. The approach against small-scale self-focusing (SSSF) of high-power lasers (HPLs) is proposed by using rotating beams generated by the coherent superposition of two vortex beams with opposite topological charges and frequency shift. The propagation model of rotating beams in the nonlinear medium is established, and the SSSF effects of the non-rotating and rotating beams are numerically simulated and comparatively analyzed. The results show that, compared with the non-rotating beam, the rotating beam can contribute to the reduction of the breakup integral and mid-high frequency components of the HPLs.

Shannon entropy method of small-scale self-focusing assessment in high-power laser systems

Through analysis of near-field beam profiles, we propose a method using Shannon entropy to assess the development of small-scale self-focusing during laser propagation and amplification in high-power laser systems. In this method, the entropy curve that corresponds to increasing B integral displays an evident turning point at which small-scale self-focusing starts to rapidly develop. In contrast to classical methods using contrast, modulation, or power spectral density, the proposed method provides the B integral criterion more clearly and objectively. This approach is an optimization method that can be utilized in the design and operation of high-power laser systems.

Grism compressor for carrier-envelope phase-stable millijoule-energy chirped pulse amplifier lasers featuring bulk material stretcher

We demonstrate compression of amplified carrier-envelope phase (CEP)-stable laser pulses using paired transmission gratings and high-index prisms, or grisms, with chromatic dispersion matching that of a bulk material pulse stretcher. Grisms enable the use of larger bulk stretching factors and thereby higher energy pulses with lower B-integral in a compact amplifier design suitable for long-term CEP control.