Mechanical-stage-free ultrafast pump-probe setup via dynamic holographic beam steering

Conventional ultrafast pump-probe setups suffer from spatial walk-off, beam pointing instability, and vibrational noise due to mechanical translation stages. To overcome these limitations, we introduce an all-optical, mechanical-stage-free holographic pump-probe technique. Utilizing a spatial light modulator (SLM), we spatially multiplex a single femtosecond beam into concentric pump and probe channels. The pump beam is holographically steered across a stationary silica wedge, translating lateral displacement into precise optical path length variations without any mechanical movement. To suppress lateral walk-off and maintain stable spatiotemporal overlap, a 4f optical relay configuration is integrated to compensate for the angular deviation induced during beam steering. This automated setup successfully executes a continuous 2.3 ps temporal scan with a 4.6 fs temporal step size. The system performance is experimentally validated through optical crosscorrelation measurements and quantitative centroid-tracking analysis of beam overlap stability.