Ultrafast spatiotemporal processing with thin-film micro-optics

Abstract

For spatiotemporal transformation and processing of ultrashort-pulse laser beams, serious design constraints arise from dispersion and diffraction. At pulse durations in 10-fs range, temporal and spatial parameters of propagating wave packets are coupled and significant inhomogeneities appear. To enable a controlled shaping or encoding and a reliable detection or decoding with 2-D spatial resolution, specific advantages of thin-film micro-optical arrays can be exploited. Transmitting and reflecting components of extremely small conical angles are used to generate multiple nondiffracting beams and self-imaging phase patterns. With novel-type metal-dielectric microaxicons, low-dispersion reflective devices are realized. Beam propagation is simulated numerically with Rayleigh-Sommerfeld diffraction theory. For ultrafast time-space conversion, matrix processors consisting of dielectric thin-film microaxicons are tested. Transversally resolving linear and nonlinear autocorrelation techniques are applied to characterize the space-time structure of localized few-cycle wave packets shaped from Ti:sapphire laser beams at pulse durations down to 8 fs. Bessel-like X waves are generated and their propagation is studied. In combination with autocorrelation, wavefront analysis of ultrashort-pulse lasers with Bessel-Shack-Hartmann sensors operated in reflection setup is demonstrated.