Laser wakefield acceleration, characterized by the extremely high electric field gradient exceeding 100\ GV/m, is regarded as a compact and cost affordable technology for the next generation of particle colliders and light sources. However, it has always been a major challenge to effectively increase the energy transfer efficiency from the laser to the accelerated beam, while ensuring the beam quality remains suitable for practical applications. This study demonstrates that the laser with shorter pulse duration allows for a two-step dechirping process of the accelerated electron beam with charge of nanocoulomb level. The electron beams with an energy spread of 5\% can be generated with the energy transfer efficiency of 10% to 30% in a large parameter space. For example, one electron beam with the energy of 420 MeV, the charge of 5.5 nC and the energy spread of  10\% can be produced using an 8.3 J laser pulse with 7.2 fs duration. 

laser, plasma, efficiency