Opt. Express 19, 11638–11653 (2011)

Ultrashort pulses with high temporal precision are needed for a variety of ultrafast optical applications. Jens Köhler and co-workers from the University of Kassel in Germany have developed an all-optical technique for realizing an extremely stable high-precision interferometer. The scheme combines a femtosecond polarization pulse shaper with a polarizer, and uses two linear spectral phase masks to mimic an ultrastable common-path interferometer. The pulse shaper comprises a double-layer liquid-crystal spatial light modulator whose polarization directions can be oriented at ±45° with respect to the polarization of the input pulse. By applying appropriate linear spectral phase functions, the researchers split the input pulse into two identical temporally delayed replicas of crossed linear polarization. A subsequent polarizer projected the polarization directions of the two pulses onto the same plane. The researchers used pulses with durations of <12 fs from an 800 nm Ti:sapphire laser to investigate the temporal precision limit of the set-up. They determined the minimum limit in achievable delay step size to be 280 zs, which means the precision of the optical path length is less than the Bohr radius of 0.529 Å, and applied the precisely generated pulse pairs to a strong-field quantum control experiment. The researchers say that this scheme might pave the way to the development of attosecond pump–probe experiments.