We experimentally generate optical vortices in the output beam of a 20-fs Ti:sapphire laser. Screw phase dislocations are imposed on the spectral components of the short pulses by aligning a computer-generated hologram in a dispersionless 4f setup.
We show that spatial phase dislocations can be generated in femtosecond laser beams by computergenerated holograms provided they are build in a setup compensating for the introduced spatial dispersion of the broad spectrum. We present analytical results describing two possible arrangements-dispersionless 4f-setup and double-pass grating compressor. Experimental results on the generation of optical vortices in the output beam of a 20fs-Ti:sapphire laser and proof-of-principle measurements with broadband-tunable cw Ti:sapphire laser confirm the theoretical predictions.
We employ a variational technique to describe the propagation of a Gaussian beam in a nonlinear, weakly nonlocal medium and derive the conditions for breathing soliton formation in both one and two transverse dimensions. The reduced one-dimensional results agree quantitatively with known exact nonlocal soliton solutions. We subsequently formulate a simple procedure for estimating the strength of a weak nonlocality and verify its applicability by direct numerical simulations.
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