Control of chirped pulse trains: a speedway for free-optimization experiments

Complex phase-only shaping of intense ultrashort laser pulses is applied to generate highly flexible pulse structures with regular envelopes. By incorporating the linear chirp as additional free parameter into the technique of colored pulses, trains of chirped pulses are produced, capable of independent and simultaneous modulation of relative intensity ratio, optical delay, and individual chirp. Such pulses might find applications in multi-parameter scans or closed-loop feedback measurements. For the latter, we demonstrate that with use of these tailored pulse trains, adaptive feedback control experiments quickly converge. They provide near-optimal solutions, already revealing key features of the system under study. Moreover, seeding standard free-optimization routines with these temporary solutions largely accelerates the search for the closest-possible optimum.