Spatially resolved amplitude and phase characterization of femtosecond optical pulses

Abstract

Ultrabroadband pulses exhibit a frequency-dependent mode size owing to the wavelength dependence of free-space diffraction. Additionally, rather complex lateral dependence of the temporal pulse shape has been reported for Kerr-lens mode-locked lasers and broadband amplifier chains and in frequency-domain pulse shapers, for example. We demonstrate an ultrashort-pulse characterization technique that reveals lateral pulse-shape variations by spatially resolved amplitude and phase measurements by use of spectral phase interferometry for direct electric-field reconstruction (SPIDER). Unlike with autocorrelation techniques, with SPIDER we can obtain spatially resolved pulse characterization even after the nonlinear process. Thus, with this method the spectral phase of the pulse can be resolved very rapidly along one lateral beam axis in a single measurement.

Far-field spectral characterization of conical emission and filamentation in Kerr media

“…On the other hand, temporal auto-correlation traces or frequency resolved optical gating (FROG) give a precise measurement of the temporal profile at the medium output of the whole (or a particular portion of the) filament [13,23,24], thus losing any information regarding the (transverse) space-dependent temporal profile. The limitations of FROG measurements have been partly overcome with the so called SPIDER technique [25] that gives the temporal profile across one spatial dimension [26] and by use of a particular 3D optical gating method [27,28] that provides the full spatio-temporal intensity profile of femtosecond pulses and has indeed allowed a full dimensional intensity space-time characterization of filaments in water [29] and of X-waves in χ (2) media [28]. Although extremely powerful, this technique requires the use of two separate, high power, synchronized laser sources, the first providing the pulse under investigation and the second a pulse that must have an appreciably shorter time duration in order to guarantee a high (temporal) resolution.…”

High-power table-top white-light few-cycle laser generator

“…By optimizing a metre-long hollow fibre at the pressure 2.5 atm, we have reduced the input 2.5 mJ pulses to 1.5 mJ behind the fibre, which indicates a high efficiency (~ 60%) for our system. To characterize the compressed output pulse, we have used a spectral phase interferometry for directly reconstructing the electric field [39] (see Fig. 1).…”

Measuring the complete spatio-temporal field of focused ultrashort laser pulses for multi-photon microscopy

“…But because digital cameras and other optoelectronic sensors are obviously limited to only two dimensions, standard techniques yield at best only 2D information, E(x,t) or E(x,y), from a single data frame. Previous attempts include linear and nonlinear spectral interferometry [18][19][20][21] , sometimes combined with frequency-resolved optical gating (FROG) 22 , direct wave-front sensing [23][24][25] , and digital holography [26][27][28] .…”