64 research outputs found
Self-calibrating d-scan: measuring ultrashort laser pulses on-target using an arbitrary pulse compressor
In most applications of ultrashort pulse lasers, temporal compressors are
used to achieve a desired pulse duration in a target or sample, and precise
temporal characterization is important. The dispersion-scan (d-scan) pulse
characterization technique usually involves using glass wedges to impart
variable, well-defined amounts of dispersion to the pulses, while measuring the
spectrum of a nonlinear signal produced by those pulses. This works very well
for broadband few-cycle pulses, but longer, narrower bandwidth pulses are much
more difficult to measure this way. Here we demonstrate the concept of
self-calibrating d-scan, which extends the applicability of the d-scan
technique to pulses of arbitrary duration, enabling their complete measurement
without prior knowledge of the introduced dispersion. In particular, we show
that the pulse compressors already employed in chirped pulse amplification
(CPA) systems can be used to simultaneously compress and measure the temporal
profile of the output pulses on-target in a simple way, without the need of
additional diagnostics or calibrations, while at the same time calibrating the
often-unknown differential dispersion of the compressor itself. We demonstrate
the technique through simulations and experiments under known conditions.
Finally, we apply it to the measurement and compression of 27.5 fs pulses from
a CPA laser.Comment: 11 pages, 5 figures, Scientific Reports, in pres
Dispersion managed mode-locking dynamics in a Ti:Sapphire laser
We present what is to our knowledge the most complete 1-D numerical analysis
of the evolution and the propagation dynamics of an ultrashort laser pulse in a
Ti:Sapphire laser oscillator. This study confirms the dispersion managed model
of mode-locking, and emphasizes the role of the Kerr nonlinearity in generating
mode-locked spectra with a smooth and well-behaved spectral phase. A very good
agreement with preliminary experimental measurements is found.Comment: 11 pages, 4 figures, submitted to Optics Letter
Temporal characterization of broadband femtosecond laser pulses by third-harmonic dispersion scan with ptychographic retrieval
We present a new variant of dispersion scan (d-scan) based on surface
third-harmonic generation (STHG) and a ptychographic algorithm taylored for
full retrieval (amplitude and phase) of broadband laser pulses. We demonstrate
the technique by temporally measuring and compressing few-cycle pulses with 7
fs and 2.5 nJ from a Ti:Sapphire oscillator, using a sapphire window as the
nonlinear medium. The results are in very good agreement with standard
second-harmonic d-scan measurements based on a nonlinear crystal. The
intrinsically broadband and phase-matching-independent nature of STHG make this
technique very suitable for the characterization of ultrashort laser pulses
over a broad wavelength range extending into the mid-infrared.Comment: 7 pages, 5 figures. Submitted to Optics Letter
Single-shot implementation of dispersion-scan for the characterization of ultrashort laser pulses
We demonstrate a novel, single-shot ultrafast diagnostic, based on the
dispersion-scan (d-scan) technique. In this implementation, rather than
scanning wedges to vary the dispersion as in standard d-scan, the pulse to be
measured experiences a spatially varying amount of dispersion in a Littrow
prism. The resulting beam is then imaged into a second-harmonic generation
crystal and an imaging spectrometer is used to measure the two-dimensional
trace, which is analyzed using the d-scan retrieval algorithm. We compare the
single-shot implementation with the standard d-scan for the measurement of
sub-3.5-fs pulses from a hollow core fiber pulse compressor. We show that the
retrieval algorithm used to extract amplitude and phase of the pulse provides
comparable results, proving the validity of the new single-shot implementation
down to near single-cycle durations.Comment: 6 pages, 4 figure
Fundamentals of Highly Non-Degenerate Cascaded Four-Wave Mixing
By crossing two intense ultrashort laser pulses with different colors in a transparent medium, like a simple piece of glass, a fan of multicolored broadband light pulses can be simultaneously generated. These newly generated pulses are emitted in several well-defined directions and can cover a broad spectral range, from the infrared to the ultraviolet and beyond. This beautiful phenomenon, first observed and described 15 years ago, is due to highly-nondegenerate cascaded four-wave mixing (cascaded FWM, or CFWM). Here, we present a review of our work on the generation and measurement of multicolored light pulses based on third-order nonlinearities in transparent solids, from the discovery and first demonstration of highly-nondegenerate CFWM, to the coherent synthesis of single-cycle pulses by superposition of the multicolored light pulses produced by CFWM. We will also present the development and main results of a dedicated 2.5-D nonlinear propagation model, i.e., with propagation occurring along a two-dimensional plane while assuming cylindrically symmetric pump beam profiles, capable of adequately describing noncollinear FWM and CFWM processes. A new method for the generation of femtosecond pulses in the deep-ultraviolet (DUV) based on FWM and CFWM will also be described. These experimental and theoretical results show that highly-nondegenerate third-order nonlinear optical processes are formally well understood and provide broader bandwidths than other nonlinear optical processes for the generation of ultrashort light pulses with wavelengths extending from the near-infrared to the deep-ultraviolet, which have many applications in science and technology
Simultaneous compression, characterization and phase stabilization of GW-level 14 cycle VIS-NIR femtosecond pulses using a single dispersion-scan setup.
[EN]We have temporally characterized, dispersion compensated and carrier-envelope phase stabilized 1.4-cycle pulses (3.2 fs) with 160 µJ of energy at 722 nm using a minimal and convenient dispersion-scan setup. The setup is all inline, does not require interferometric beamsplitting, and uses components available in most laser laboratories. Broadband minimization of third-order dispersion using propagation in water enabled reducing the compressed pulse duration from 3.8 to 3.2 fs with the same set of chirped mirrors. Carrier-envelope phase stabilization of the octave-spanning pulses was also performed by the dispersion-scan setup. This unprecedentedly simple and reliable approach provides reproducible CEP-stabilized pulses in the single-cycle regime for applications such as CEP-sensitive spectroscopy and isolated attosecond pulse generation
Characterization of broadband few-cycle laser pulses with the d-scan technique
We present an analysis and demonstration of few-cycle ultrashort laser pulse characterization using second-harmonic dispersion scans and numerical phase retrieval algorithms. The sensitivity and robustness of this technique with respect to noise, measurement bandwidth and complexity of the measured pulses is discussed through numerical examples and experimental results. Using this technique, we successfully demonstrate the characterization of few-cycle pulses with complex and structured spectra generated from a broadband ultrafast laser oscillator and a high-energy hollow fiber compressor. (C)2012 Optical Society of Americ
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