Spectral self-imaging and Gouy rotation echoes of propagating vortex pulse arrays

摘要

Recently it was reported that free-space propagating, ultrashort-pulsed polychromatic beams with orbital angularmomentum (OAM) show a spectral Gouy rotation (SGR) of red- and blue-shifted areas around singularities. Infemtosecond laser experiments with different types of spiral phase gratings, pulse propagation in spectral domain wasstudied with high resolution and sensitivity. By analyzing maps of spectral moments it was found that the interference ofmultiple OAM beams leads to a periodical revival of SGR by diffractive Talbot self-imaging. If the wavefront twist ofthe sub-beams is synchronized (co-rotating vortices), an optimum performance is found. In contrast, SGR echoes ofcounter-rotating beams are periodically distorted by destructive interference. Thus, the fine structure of self-imagedspectral maps enables to sort partial beams from interference patterns by even extremely weak imprinted vorticityinformation. It may further have implications for highly nonlinear processes and opens new prospects for applications inmetrology, optical computing, or interferometry.