Benjamín Alonso

Universidad de Salamanca · Department of Applied Physics

Spatiotemporal sculpturing of light pulse with ultimately sophisticated structures represents the holy grail of the human everlasting pursue of ultra-fast information transmission and processing as well as ultra-intense energy concentration and extraction. It also holds the key to unlock new extraordinary fundamental physical effects. Traditionally...

In this work, we use the amplitude swing technique to retrieve ultrashort vector pulses, i.e., those which exhibit time-varying polarization.

There is a growing interest in obtaining robust ultrashort temporal characterization techniques able to operate in different spectral ranges with different pulse bandwidths. Here we demonstrate that the recently introduced amplitude swing technique can measure ultrashort laser pulses in different spectral regions over more than one octave from the...

Spatiotemporal sculpturing of light pulse with ultimately sophisticated structures represents the holy grail of the human everlasting pursue of ultrafast information transmission and processing as well as ultra-intense energy concentration and extraction. It also holds the key to unlock new extraordinary fundamental physical effects. Traditionally,...

We show the versatility of the bulk lateral shearing interferometer characterizing complex spatiotemporal structures in different spectral ranges. Specifically, we have characterized constant and timevarying optical vortices in the visible and near infrared spectral ranges respectively. The high stability of the system combined with its spectral ve...

The spatiotemporal measurement of ultrashort laser beams usually involves techniques with complex set-ups or limited by instabilities that are unable to accurately retrieve the frequency-resolved wavefront. Here, we solve these drawbacks by implementing a simple, compact, and ultra-stable spatiotemporal characterization technique based on bulk late...

We implement an in-line and ultrastable spatiotemporal technique based on uniaxial crystals, which solves high-complexity and stability problems associated with other techniques. Moreover, we generate and characterize the temporally resolved wavefronts of time-varying optical vortices.

Mode-locked erbium-doped fibre lasers are ultrashort pulsed sources widely studied due to their versatility and multiple applications in the near infrared range. Here we present the experimental study of the emission of a passive mode-locked erbium-doped fibre laser with an amplification stage outside the cavity by means of Frequency Resolved Optic...

Over the past decades, the use of ultrafast laser beams at a highly varied range of applications (e.g., biophotonics, material science, telecommunications, physics, chemistry, etc.) has evolved, demanding more complex light structures not only in time (i.e., ultrafast pulses), but also spatiotemporally and in polarization (e.g., vector beams, time...

Special light beams exhibiting a structured field and carrying orbital angular momentum (OAM) appear as interesting tools in different fields such as particle manipulation, telecommunications or in several areas of light-matter interaction, including materials processing and nonlinear optics, among others. A very interesting possibility of these sp...

The dispersion scan (d-scan) technique has emerged as a simple-to-implement characterization method for ultrashort laser pulses. D-scan traces are intuitive to interpret and retrieval algorithms that are both fast and robust have been developed to obtain the spectral phase and the temporal pulse profile. Here, we shortly review the second harmonic...

In this work we firstly study the influence of different parameters in the temporal characterization of ultrashort laser pulses with the recently developed amplitude swing technique. In this technique, the relative amplitude of two delayed replicas is varied while measuring their second-harmonic spectra. Here we study the retrieval of noisy traces...

The use of structured ultrashort pulses with coupled spatiotemporal properties is emerging as a key tool for ultrafast manipulation. Ultrafast vector beams are opening exciting opportunities in different fields such as microscopy, time-resolved imaging, nonlinear optics, particle acceleration or attosecond science. Here, we implement a technique fo...

The dispersion scan (d-scan) technique has emerged as a simple-to-implement characterization method for ultrashort laser pulses. D-scan traces are intuitive to interpret and retrieval algorithms that are both fast and robust have been developed to obtain the spectral phase and the temporal pulse profile. Here, we give a review of the d-scan techniq...

We demonstrate a novel dispersion-scan (d-scan) scheme for single-shot temporal characterization of ultrashort laser pulses. The novelty of this method relies on the use of a highly dispersive crystal featuring antiparallel nonlinear domains with a random distribution and size. This crystal, capable of generating a transverse second-harmonic signal...

A method of ultrashort laser pulse reconstruction is presented, consisting on the analysis of the nonlinear signal obtained from the interference of the pulse with a replica of itself at a given time delay while varying the relative amplitude between the pulses. The resulting spectral traces are analyzed both analytically and numerically, showing t...

We use self-calibrating dispersion scan to experimentally detect and quantify the presence of pulse train instabilities in ultrashort laser pulse trains. We numerically test our approach against two different types of pulse instability, namely second-order phase fluctuations and random phase instability, where the introduction of an adequate metric...

We demonstrate a novel dispersion-scan (d-scan) scheme for single-shot temporal characterization of ultrashort laser pulses. The novelty of this method relies on the use of a highly dispersive crystal featuring antiparallel nonlinear domains with a random distribution and size. This crystal, capable of generating a transverse second-harmonic signal...

We apply the self-calibrating d-scan technique to quantify the pulse train instabilities in a fiber laser with supercontinuum generation in a photonic crystal fiber (PCF). Using an all-normal dispersion PCF, stable 15-fs pulses are measured.

We perform a complete measurement of ultrashort pulsed beams where the polarization evolves spatially and temporally. We apply our technique to characterize ultrafast shaped vector beams which combine temporal polarization gating and radial polarization.

We present a new concept for temporal pulse measurement, the amplitude swing, based on the amplitude variation of two delayed pulse replicas. The in-line compact set-up is versatile for pulses with different durations and bandwidths.

We apply the self-calibrating d-scan technique to quantify the pulse train instabilities in a fiber laser with supercontinuum generation in a photonic crystal fiber (PCF). Using an all-normal dispersion PCF, stable 15-fs pulses are measured.

We perform a complete measurement of ultrashort pulsed beams where the polarization evolves spatially and temporally. We apply our technique to characterize ultrafast shaped vector beams combining temporal polarization gating and radial polarization.

We present a new concept for temporal pulse measurement, the amplitude swing, based on the amplihrde variation of two delayed pulse replicas. The in-line compact set-up is versatile for pulses with different durations and bandwidths.

The use of structured ultrashort pulses with coupled spatiotemporal properties is emerging as a key tool for ultrafast manipulation. In particular, the ultrafast vector beams are opening exciting opportunities in different fields such as microscopy, time-resolved imaging, nonlinear optics, particle acceleration or attosecond science. We propose and...

Dispersion effect in the propagation of pulses through cladding waveguides. • Spatio-spectral and-temporal structure of pulses at the output of waveguides. • A different behavior between mono-modal and multi-modal waveguides is reported. A B S T R A C T Inscription of optical waveguides by direct femtosecond laser irradiation has become a very vers...

Focusing control of ultrashort pulsed beams is an important research topic, due to its impact to subsequent interaction with matter. In this work, we study the propagation near the focus of ultrashort laser pulses of ~25 fs duration under diffractive focusing. We perform the spatio-spectral and spatio-temporal measurements of their amplitude and ph...

The growing use of ultrashort laser pulses exhibiting time-varying polarization (vector pulses) demands simple and robust characterization techniques capable to perform measurements in a broad range of experimental and environmental conditions. Here we present in-line, single-channel setup based on spectral interferometry to characterize ultrashort...

Focusing control of ultrashort pulsed beams is an important research topic, due to its impact to subsequent interaction with matter. In this work, we study the propagation near the focus of ultrashort laser pulses of ~25 fs duration under diffractive focusing. We perform the spatio-spectral and spatio-temporal measurements of their amplitude and ph...

In many ultrafast applications, ultrashort pulse lasers are combined with temporal compressors to achieve a desired pulse duration in a target or sample. Precise temporal characterization is important for knowing the actual pulse shape and optimizing the compression itself. The dispersion-scan (d-scan) technique is a recent approach for the simulta...

Gas-filled hollow-core fiber pulse post-compressors capable of generating few- to single-cycle pulses are a key enabling tool for attosecond science and ultrafast spectroscopy. Achieving optimum performance at such short pulse durations can be extremely challenging since it requires both the means to compensate the spectral phase of the pulses over...

Intense few- and single-cycle pulses are powerful tools in different fields of science Today, third- and higher-order terms in the remnant spectral phase of the pulses remain a major obstacle for obtaining high-quality few- and single-cycle pulses from in-line post-compression setups. In this Letter, we show how input pulse shaping can successfully...

Intense few- and single-cycle pulses are powerful tools in different fields of science Today, third- and higher-order terms in the remnant spectral phase of the pulses remain a major obstacle for obtaining high-quality few- and single-cycle pulses from in-line post-compression setups. In this Letter, we show how input pulse shaping can successfully...

In this work we study the impact of chromatic focusing of few-cycle laser pulses on high-order harmonic generation (HHG) through analysis of the emitted extreme ultraviolet (XUV) radiation. Chromatic focusing is usually avoided in the few-cycle regime, as the pulse spatio-temporal structure may be highly distorted. Here, however, we demonstrate it...

We present observations of the emission of XUV continua in the 20–37-eV region by high-harmonic generation with 4–7-fs pulses focused onto a Kr gas jet. The underlying mechanism relies on coherent control of the relative delays and phases between individually generated attosecond pulses, achievable by adjusting the chirp of the driving pulses and t...

We present evidence for self-stabilization of the relative spectral phase of high-order harmonic emission against intensity variations of the driving field. Our results demonstrate that, near the laser focus, phase matching of the harmonic field from a macroscopic target can compensate for the intensity dependence of the intrinsic phase of the harm...

We present observations of the emission of XUV supercontinua in the 20-37 eV region by high harmonic generation (HHG) with 4-7 fs pulses focused onto a Kr gas jet. The underlying mechanism relies on coherent control of the relative delays and phases between individually generated attosecond pulses, achievable by adjusting the chirp of the driving p...

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 mi...

We present, for the first time, the complete pulse characterization of the infrared pulse after generating harmonics. A systematic study of the high harmonic generation process, and the generating infrared pulse characterization, has been done by changing the focus-gas-jet relative position. We have concluded, supported by nonlinear propagation sim...

We present a complete experimental characterization and simulation of the spatiotemporal and spatio-spectral effects taking place when a femtosecond pulse is shaped by a diffractive optical element.

We have post-compressed 25 fs (Fourier limit) amplified pulses in an argon-filled hollow-core fiber. The output pulses were compressed using a pair of wedges and chirped mirrors down to 4.5 fs (Fourier limit of 4.1 fs), which corresponds to less than two optical cycles. We then performed the characterization of the pulses by combining the d-scan an...

The temporal characterization of few-cycle pulses is of paramount importance for advanced applications, such as attosecond physics. However, their large bandwidths can pose significant challenge for usual diagnostic techniques. Moreover, the methods for their generation - e.g. hollow-core fiber compression [1] - often lead to spatial inhomogeneitie...

When a high-power infrared femtosecond pulse is focused into a transparent solid, different non-linear effects such as self-phase modulation, self-steepening, plasma generation or filamentation take place. These effects usually give rise to an extreme spectral broadening of the pulse that is termed supercontinuum (SC) generation. This contribution...

We provide the retrieved pulse for optimum wedge insertion (maximum compression) conditions and correct its time evolution due to the spectral phase having been wrongly assigned the opposite sign in our previous paper [Opt. Express 20, 17880 (2012)]. These changes do not affect the conclusions of the paper.

This thesis is devoted to the development of a technique for the measurement of the spatiotemporal amplitude and phase of ultrashort laser pulses and its applications. The core of the thesis is divided into three parts, which correspond to the presentation of the technique (Part I), its applications to diffractive optics (Part II) and to nonlinear...

Few-cycle pulses (~8 fs) from an oscillator were spatiotemporally characterized with STARFISH. The reference pulse was calibrated with the d-scan technique. The evolution of the focused pulses after an off-axis parabolic mirror was studied in detail.

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...

In this work we demonstrate the ability of the spatiotemporal characterization technique STARFISH to retrieve the wavelength dependent wavefront of focused ultrashort laser pulses. The high resolution achievable with this technique allows measuring the wavefront at the focal spot. In particular, the method is applied to study the effects of focusin...

In this paper we apply a broadband fiber optic coupler interferometer to the measurement of few-cycle laser pulses. Sub-8-fs pulses delivered by an ultrafast oscillator were characterized spatiotemporally using STARFISH, which is based on spatially resolved spectral interferometry. The reference pulse was measured with the d-scan technique. The pul...

We demonstrated a simple diffractive method to map the self-similar structure shown in squared radial coordinate of any set of circularly symmetric fractal plates into self-similar light pulses in the corresponding temporal domain. The space-to-time mapping of the plates was carried out by means of a kinoform diffractive lens under femtosecond illu...

We present a technique for efficient generation of the second-harmonic signal at several points of a nonlinear crystal simultaneously. Multispot operation is performed by using a diffractive optical element that splits the near-infrared light of a mode-locked Ti:sapphire laser into an arbitrary array of beams that are transformed into an array of f...

The energy scaling up of pulse postcompression is still an open issue. In this work we analyze the use of astigmatic focusing to improve the output pulses in a filamentation based postcompression setup. Unlike spherical conditions, astigmatic focusing enhances the output energy and the spectral broadening of the filament. This is due to the increas...

The full description of the evolution of light during its nonlinear propagation represents a valuable help to the complete understanding of important nonlinear phenomena such as light filamentation. In this paper we present a comparison between theoretical and experimental results of the spatiotemporal structure of a light filament at different pro...

Export Date: 11 February 2013, Source: Scopus, Art. No.: 5981470

Export Date: 11 February 2013, Source: Scopus, Art. No.: 5981457

In the last decade the use of laser beam filamentation has become of great interest, not only as a complex physical process, but also applied to the compression of femtosecond pulses. In particular, it has been reported that at some particular experimental conditions the pulse can experience a self-compression effect [1]. This phenomenon has been r...

Export Date: 11 February 2013, Source: Scopus, Art. No.: 5942797

We have designed and developed a pulse compressor with volume transmission holographic gratings to be implemented in post-compression experiments based on filamentation in gases. Pulse compression down to 13fs has been demonstrated. The gratings have been recorded in commercial PFG-04 dichromated gelatin emulsions with a recording wavelength of 532...

Self-compressed (SC) pulses have been achieved through the filamentation process in air without any additional dispersion compensation, using the input pulse chirp as the control parameter. For any studied input pulse energy (3-5 mJ), we have found two opposite sign input group-delay dispersion values for which SC pulses can be achieved systematica...

A study of second harmonic generation of femtosecond pulses focused with diffractive lenses is presented; the central wavelength of the SH can be tuned by changing the relative distance between the lens and the crystal.

The influence of the input pulse chirp and energy on the filamentation process is studied. Output beam profiles, spectra and energies were systematically measured by changing the pulse chirp for different input energies. Amap of the different energy-chirp regions was compiled. It shows that high-energy stable single filament can be obtained by usin...

We carry out a complete spatio-temporal characterization of the electric field of an ultrashort laser pulse after passing through a diffractive optical element composed of several binary amplitude concentric rings. Analytical expressions for the total diffraction field in the time and spectral domain are provided, using the Rayleigh-Sommerfeld form...

We have investigated femtosecond multi-filamentation process in a mixture of gases controlling the concentration of atoms versus molecules in the gas cell. The experimental results show that this control could provide a new freedom degree to deterministic spatial distribution control of the multiple filaments. Our simulation indicates surprisingly...