Controlling the Spatio-Temporal Distribution of Ultrashort Pulses Near Focus by Means of Diffractive Focusing and Pulse Shaping

Focusing of ultrashort pulses is an important issue for their applications. Even if free aberration focusing is generally desired to obtain at focus the shorter durations and the higher intensities, the ability to create and control other spatio-temporal radiance patterns can be helpful, or even required, on diverse applications (nonlinear optics, particle acceleration, etc.). For instance, when focused by diffractive elements, ultrashort pulses can show complex spatio-temporal structures [1]. In the present work, we gain a further control over the focusing by shaping the spectral phase of the input pulses. For this purpose, we combine the focusing by a kinoform diffractive lens (KDL) with the control of the spectral phase of the input pulses, to tailor different spatio-temporal patterns of intensity [2]. We have studied spatio-temporal patterns along the propagation at the focal region, for specific values (negative, zero and positive) of second (GDD) and third order dispersion (TOD), introduced by an acousto-optic device to the pulse prior focusing.