We experimentally demonstrate spatial light modulation based on graded-index plasma channels induced by femtosecond pulses. The spatial profile of the probe beam can be conveniently controlled by adjusting the intensity distribution of the pump beam or by changing the relative position between pump beam and probe beam. We also show that the modulation depth of the probe beam can be controlled by adjusting the power of the pump beam.
We experimentally show a method for pulse-width measurement. Pulse widths at different partial positions of an
ultrashort-pulsed beam are measured, results show that pulse widths in the center of the beam are less than that of in the
edge because of the existence of residual chirp. We also investigate the temporal evolution at a strongest spatial modulation
position of the beam during small-scale self-focusing, it finds that its pulse width decreases as power increases due to a
spatiotemporal coupling effect. We find that this method not only can be used to accurately measure the pulse width at any
one spatial position of the beam, but also be useful for real-time monitoring of spatial-temporal evolution.