Single-frame measurement of the complete spatio-temporal intensity and phase of ultrashort laser pulse(s) using wavelength-multiplexed digital holography

We show that a simple (few-element) arrangement for wavelength-multiplexed digital holography allows the measurement of the electric field E͑x , y , t͒ of a femtosecond laser pulse on a single shot. A slightly rotated twodimensional diffractive optical element and a variable-wavelength filter together generate multiple spectrally resolved digital holograms that are simultaneously captured in a single frame by a digital camera. An additional simultaneous measurement of the spectral phase for a spatially filtered replica of the pulse with frequency-resolved optical gating completes this three-dimensional measurement. An experimental implementation of the technique is presented and its current limitations are discussed

Determining Error Bars in Measurements of Ultrashort Laser Pulses

We present a simple and automatic method for determining the uncertainty in the retrieved intensity and phase versus time (and frequency) due to noise in a frequency-resolved optical-gating trace, independent of noise source. It uses the ‘‘bootstrap’’ statistical method and also yields an automated method for phase blanking (omitting the phase when the intensity is too low to determine it)

The coherent artifact in modern pulse measurements

We simulate multi-shot intensity-and-phase measurements of unstable ultrashort-pulse trains using frequency-resolved-optical-gating (FROG) and spectral phase interferometry for direct electric-field reconstruction (SPIDER). Both techniques fail to reveal the pulse structure. FROG yields the average pulse duration and suggests the instability by exhibiting disagreement between measured and retrieved traces. SPIDER under-estimates the average pulse duration but retrieves the correct average pulse spectral phase. An analytical calculation confirms this behavior.Comment: submission to Opt. Let

Relative-phase ambiguities in measurements of ultrashort pulses with well-separated multiple frequency components

Ultrashort-pulse characterization techniques, such as the numerous variants of frequency-resolved optical gating (FROG) and spectral phase interferometry for direct electric-field reconstruction, fail to fully determine the relative phases of well-separated frequency components. If well-separated frequency components are also well separated in time, the cross-correlation variants (e.g., XFROG) succeed, but only if short, wellcharacterized gate pulses are used

All-fiber ultrafast amplifier at 1.9 μm based on thulium-doped normal dispersion fiber and LMA fiber compressor

The duration reduction and the peak power increase of ultrashort pulses generated by all-fiber sources at a wavelength of 1.9 µm are an urgent tasks. Finding an effective and easy way to improve these characteristics of ultrafast lasers can allow a broad implementation of wideband coherent supercontinuum sources in the mid-IR range required for various applications. As an alternative approach of sub-100 fs pulse generation we present an ultrafast all-fiber amplifier based on a normal-dispersion germanosilicate thulium-doped active fiber and a large-mode-area silica-fiber compressor. The output pulses have the following characteristics: the pulse duration of 71 fs, the central wavelength of 1.9 µm, the repetition rate of 23.8 MHz, the energy per pulse period of 25 nJ, the average power of 600 mW, the maximum estimated peak power of 220 kW, and a random output polarization. The pulse intensity and phase profiles were measured via the second-harmonic-generation frequency-resolved optical gating technique. The dynamics of ultrashort pulses propagation in the amplifier was analyzed using numerical simulation

Simultaneously measuring two ultrashort laser pulses on a single-shot using double-blind frequency-resolved optical gating

We demonstrate a simple self-referenced single-shot method for simultaneously measuring two different arbitrary pulses, which can potentially be complex and also have very different wavelengths. The method is a variation of cross-correlation frequency-resolved optical gating (XFROG) that we call double-blind (DB) FROG. It involves measuring two spectrograms, both of which are obtained simultaneously in a single apparatus. DB FROG retrieves both pulses robustly by using the standard XFROG algorithm, implemented alternately on each of the traces, taking one pulse to be ?known? and solving for the other. We show both numerically and experimentally that DB FROG using a polarization-gating beam geometry works reliably and appears to have no nontrivial ambiguities

Roadmap on ultrafast optics

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