Bubble Elongation and Laser slicing in Strongly-Mismatched Regime of Self-Guided Nonlinear Laser-Plasma Acceleration*

A strongly mismatched regime of self-guided laser-plasma acceleration is revealed to be behind a wide-range of groundbreaking experiments. The strong mismatch, in contrast with the matched condition, arises from the incident laser spot-size being much larger than that needed for equilibration of the laser ponderomotive and electron-ion charge-separation force. A nonlinear envelope equation is used to model the steepening of laser radial envelope oscillations. In a steepened squeeze phase, rapid increase in laser intensity leads to the slicing of laser into a strong optical-shock state. As a response to the optical-shock state the acceleration structure elongates rapidly which self-injects high-quality beams. This work thus uncovers a generalized regime that has been favored by many laser-plasma acceleration experiments and opens a novel pathway for future investigations.