We demonstrate an experimentally simple and high-spectral-resolution version of spectral interferometry (SEA TADPOLE) that can measure complicated pulses (in time) at video rates. Additionally, SEA TADPOLE can measure spatial information about a pulse, and it is the first technique that can directly measure the spatiotemporal electric field ͓E͑x , y , z , ͔͒ of a focusing ultrashort pulse. To illustrate and test SEA TADPOLE, we measured E͑͒ of a shaped pulse that had a time-bandwidth product of approximately 100. To demonstrate that SEA TADPOLE can measure focusing pulses, we measured E͑x , ͒ at and around the focus produced by a plano-convex lens. We also measured the focus of a beam that had angular dispersion present before the lens. We have found that SEA TADPOLE can achieve better spectral resolution than an equivalent spectrometer, and here we discuss this in detail, giving both experimental and simulated examples. We also discuss the angular acceptance and spatial resolution of SEA TADPOLE when measuring the spatiotemporal field of a focusing pulse.
The spatio-temporal coupling of shaped laser pulses is measured using scanning SEA TADPOLE as a function of propagation distance through the focal region of a plano-convex lens. A double pulse sequence is measured to have a gradually changing spectral phase across the beam front as a function of propagation distance. When a sinusoidal spectral phase is applied to the shaper a saw-tooth spectral amplitude is measured across the beam front before and after the focal plane of the lens. The measured spatio-spectral phase and amplitude for these two common pulse shapes are consistent with the predictions of a theoretical model.
Simultaneous spatial and temporal focusing pulses are created using parametric pulse shaping and characterized with scanning SEA TADPOLE. Multiple foci are created with optically-controlled longitudal and transverse spatial positions. The characterized foci are in agreement with the predictions of a Fourier optics model. The measurements reveal significant pulse front tilt resulting from the simultaneous spatial and temporal focusing optics.
Multiple foci are created along the propagation direction of a laser beam using simultaneous spatial and temporal focusing of an ultrafast laser pulse in conjunction with parametric pulse shaping. The pulses are characterized with scanning SEA TADPOLE. The longitudinal and transverse positions of the foci are controlled using phase and amplitude shaping in a 4-f laser pulse shaping system. Measurements of the pulse duration as a function of spatial position of the foci are in agreement with the predictions of a Fourier optics model.
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