Simple devices for measuring complex ultrashort pulses

Abstract

We describe experimentally simple, accurate, and reliable methods for measuring from very simple to potentially very complex ultrashort laser pulses. With only a few easily aligned components, these methods allow the measurement of a wide range of pulses, including those with time-bandwidth products greater than 1000 and those with energies of only a few hundred photons. In addition, two new, very simple methods allow the measurement of the complete spatio-temporal intensity and phase of even complex pulses on a single shot or at a tight focus.Side views of an ultrashort laser pulse focusing in the presence of spherical aberration and group-velocity dispersion (GVD) and measured by Pamela Bowlan using SEA TADPOLE. In the nine snapshots, the color indicates the actual pulse color vs. space and time before and after the focus. The white dots represent the pulse-front (the highest intensity for a given transverse coordinate). The fringes in the beam before the focus are due to spherical aberration, and the rainbow-like appearance is due to the GVD. A short pre-history of ultrashort-laser-pulse measurementIn the 1960s, researchers began generating laser pulses shorter than could be measured using electronic detectors, and the field of ultrashort-laser-pulse measurement was born. How to measure humankind's shortest events? The goal was (and still is) to measure the pulse electric field vs. time, that is, its intensity, I(t), and phase, φ(t):or, equivalently, in the frequency domain, the pulse spectrum, S(ω), and spectral phase, ϕ(ω):Ẽomitting the negative-frequency component of the pulse. In principle, a shorter event is necessary to make the measurement. But clearly no such event was available. Researchers quickly realized that the shortest event available was the event itself. Thus autocorrelation [1] was born. Autocorrelation involved splitting the pulse into two, spatially overlapping the two pulses in some instantaneously responding nonlinear-optical medium, such as a secondharmonic-generation (SHG) crystal (See Fig. 1), and variably delaying one pulse with respect to the other. A SHG crystal produces light at twice the frequency of the input

Blue Femtosecond Pulse Generated in Periodically Poled Lithium Tantalite

“…The maximum pulse energy is about 1 mJ. We use GRENOUILLE technique to characterize the pulse [30,32,33]. Fig.…”

Quadratic spatial solitons generated in periodically poled lithium tantalite

“…6 are driven by the inherent spatiotemporal dynamics generated in the upconversion and downconversion processes, and a small amount of spatiotemporal noise can lead to multiple solitons into random patterns. [21][22][23][24] All the images exhibit irregular shapes and the different spots carry different energies. Multiple solitons were observed near phase matching, which might attribute to anisotropic diffraction in crystal and asymmetries in the input beam.…”

“…The temporal and spectral characteristics of the quadratic spatial solitons are measured by using grating-eliminated nononsense observation of ultrafast incident laser light e-fields (GRENOUILLE) technique. 21,22 2 Theory Quadratic spatial solitons consist of beams which are strongly coupled by second-order nonlinearities under the conditions of wave-vector conservation. Here, we consider a nonlinear optical system with two beams.…”

The generation and utilisation of half‐cycle cut‐offs in high harmonic spectra

“…Therefore, the three-dimensional integral over p in Eq. (14) can be eliminated by selecting the saddle-point momenta, p s (; t r ) = l e Z tr tr A(t H ) dt H : (17) This step is generally taken, and is done so in this review, when calculating the HHG spectra using the SFA. The SPA can be further applied to eliminate the integrals over t r and [45].…”

“…However, although impressive, this is a complex technique requiring the prior production of a sub-femtosecond XUV pulse and a large number of measurements (typically over a thousand, with each measurement averaged over a thousand shots). Alternatively, the amplitude and phase of the pulse's spectral envelope can be retrieved using techniques such as frequency resolved optical gating (FROG) [16] (see e. g. [17] for a review) and spectral phase interferometry for direct electricfield reconstruction (SPIDER) [18]. However, the values of the spectral phase found through such techniques are relative, leaving the absolute phase ambiguous.…”