Abstract
A self-referenced technique based on digital holography and frequency-resolved optical gating is proposed in order to characterize the complete complex electric field E (x, y, z, t) of a train of ultrashort laser pulses. We apply this technique to pulses generated by a mode-locked Ti:Sapphire oscillator and demonstrate that our device reveals and measures common linear spatio-temporal couplings such as spatial chirp and pulse-front tilt.
Highlights
Ultrashort-pulse measurement devices are usually based on a representation of the electric field as a function of time only, and as a result the spatial beam profile is often regarded as an independent measurement
We studied spatial chirp because an independent measurement was readily available in this case: a spatially-resolved spectrum is a measurement of S(x,ω), and of spatial chirp along x
We have presented a general method to measure the complete complex the electric field of a train of ultrashort pulses, with a resolution of δ x ×δ y ×δλ = 50 μm × 50μm × 4 nm, and a frame size of 100 ×100 × 50
Summary
Ultrashort-pulse measurement devices are usually based on a representation of the electric field as a function of time only, and as a result the spatial beam profile is often regarded as an independent measurement. Variations of SI have been reported where a shear is introduced in space [5], or in frequency [6], or both [7] This last device yields a self-referenced measurement of the phase function φ(x,ω). Numerous intensity-and-phase spatial-measurement techniques are available for monochromatic beams, such as direct wavefront sensing [9], or lateral shearing interferometry [10] Digital holography is another versatile spatial-characterization technique. Digital holographic measurements have been performed at different wavelengths, sequentially [11], or simultaneously, both with continuous-wave and nanosecond-pulsed laser sources [12, 13], or at different times, on the picosecond time scale [14] In these experiments, the phase function was not measured versus frequency, or time, and they do not constitute a complete measurement of the electric field. We first discuss the theoretical foundations of the method, before applying it to experimental laser pulses with common spatiotemporal couplings, such as spatial chirp and pulse-front tilt
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