To mitigate inhomogeneous thermal and stress effects caused by multi-pulse accumulation in laser-material interactions, we propose an all-optical strategy to generate a structured beam termed "drill-like laser", featuring its petal-shape intensity profile with stochastic rotation by shot-to-shot.The strategy involves generating collinear signal and idler pulses carrying conjugated orbital angular momenta via optical parametric amplification (OPA).The pulses then interfere with each other to form a beam with petal-shaped intensity structure, whose orientation is governed by their carrier-envelope phase (CEP) difference.The strategy is further implemented with a dual-stage OPA system pumped by an 800Hz-30fs-800nm femtosecond laser, where the CEP difference is directly controlled by the pump CEP.Experimentally, a drilllike laser at 1.6 m is demonstrated with stochastic shot-to-shot intensity rotation, resulting from the shot-to-shot random fluctuation of the pump CEPs, which has been validated using dual-line pump-probe detection via sum-frequency generation.Crucially, since the interference arises from two beams with free-space eigenmodes, rather than angular-dispersion-based spatiotemporal coupling, the drill-like laser maintains high propagation stability and is scalable in power by conventional laser amplification, holding great potential for applications in precision laser processing and other high-field scenarios.
Wu et al. (Tue,) studied this question.