Abstract
Recent rapid advances in spatiotemporal optical pulses demand accurate characterization of the spatiotemporal structure of the produced light fields. We report an automated close-loop characterization system that is capable of reconstructing the three-dimensional intensity and phase structures of spatiotemporal wavepacket illustrated by characterizing spatiotemporal optical vortex in the spatiotemporal domain. The characterization technique is based on interfering a much shorter probe pulse with different slices of the object wavepacket along the temporal axis. A close-loop control program is developed to realize full automation of the data collection and reconstruction process. Experimental results of the intensity and phase distributions show that the designed close-loop system is efficient in quantitatively characterizing the generated spatiotemporal optical vortex. Such a linear characterization system can also be extended to measure many other kinds of spatiotemporal wavepacket and may find broad applications in spatiotemporal wavepacket studies.
Highlights
Optical vortex beam carrying orbital angular momentum (OAM) is widely known as a beam with phase singularity caused by a spiral wavefront [1,2,3]
Time delay of the probe pulse is adjusted by an electronically controlled translation stage to make the probe pulse interfere with the different slice of object wavepacket along the temporal axis
One pulse divided from the picosecond pulse laser is directed into the pulse shaper to create the spatiotemporal optical vortex (STOV) as the object wavepacket, while the other pulse is compressed to serve as the probe pulse
Summary
Optical vortex beam carrying orbital angular momentum (OAM) is widely known as a beam with phase singularity caused by a spiral wavefront [1,2,3]. The deformations caused by transmissive SLMs with nonlinear and incomplete phase modulation could be corrected by modifying the numerical optimization coherent phase diversity to improve on-axis optical vortex generation [24] These traditional OAM can be measured by adopting the interference and diffraction properties of optical vortex [25]. We present a close-loop characterization system that is capable of reconstructing the 3D intensity structure of STOV in ST domain and extracting its ST helical phase simultaneously This linear characterization technique is based on the interference of a much shorter compressed probe pulse with the ST wavepacket to be characterized. The three-dimensional reconstruction method is based on a noncollinear first-order cross-correlation [30,31,32,33] This linear optical approach is simple to implement and suitable for the measurement of many kinds of pulses. We can reconstruct the 3D ST structure of an STOV by stitching the intensity and phase of each time slice, which are obtained by processing the corresponding experimental data
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