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