Spatio-temporal processing of femtosecond laser pulses with thin film micro-optics

Abstract

For spatio-temporal processing of ultrashort-pulse laser beams, design constraints arise from dispersion and diffraction. In sub-10-fs region, temporal and spatial coordinates of propagating wavepackets get non-separable. To enable controlled shaping and detection with spatial resolution, specific advantages of thin-film microoptical arrays are exploited. Transmitting and reflecting components of extremely small conical angles were used to generate multiple nondiffracting beams and self imaging patterns. With novel-type metal-dielectric microaxicons, low-dispersion reflective devices were realized. Beam propagation was simulated with Rayleigh-Sommerfeld diffraction theory. For time-space conversion, matrix processors consisting of thin-film microaxicons were tested. Transversally resolving linear and nonlinear autocorrelation techniques were applied to characterize the space-time-structure of localized few-cycle wavepackets shaped from Ti:sapphire laser beams at pulse durations down to 8 fs. Bessel-like X-waves were shaped and their propagation was studied. In combination with autocorrelation, wavefront analysis of ultrashort-pulse lasers with Bessel-Shack-Hartmann sensors operated in reflection setup was demonstrated.