arXiv subjects

Ammar Hideur

Publications and source records attributed to Ammar Hideur.

5 recordsLinked to original sources

arXiv2026

A Compact High-Repetition-Rate Intense THz Source for Atomic-Scale Materials Characterization

High-intensity terahertz (THz) sources combining high repetition rates, strong field amplitudes, and long-term stability are key enabling technologies for next-generation ultrafast photonics. However, simultaneously achieving these characteristics in a compact and practical architecture remains a major challenge. Here, we report a high-performance tabletop THz source delivering intense single-cycle pulses at 100 kHz, generated by optical rectification in lithium niobate using an optimized echelon-based tilted-pulse-front scheme and driven by an industrial-grade ytterbium laser. The source achieves optical-to-THz conversion efficiencies exceeding 0.13% at room temperature, peak electric fields of several hundred kV/cm, and excellent long-term stability, establishing a robust platform for high-average-power strong-field THz applications. As a proof of concept, the source was integrated into an atom probe tomography (APT) instrument. APT reconstructs the three-dimensional chemical composition of materials through field-induced ion emission from a sharp nanotip. While THz-assisted ion emission has been shown to improve analytical performance by reducing thermal effects, previous demonstrations were limited to low-repetition-rate THz sources, restricting throughput and accessible analysis volumes. Using an aluminum nanotip, we demonstrate efficient THz-assisted APT at 100 kHz and benchmark its performance against conventional voltage- and laser-assisted operation. The high repetition rate enables rapid large-volume acquisition while improving mass resolving power, reducing thermal tailing, and preserving high-quality three-dimensional reconstructions. Beyond APT, this work establishes a compact and scalable high-repetition-rate THz platform for strong-field physics, nonlinear THz photonics, ultrafast spectroscopy, and material characterization at the nanoscale.

cond-mat.mtrl-sci↗

arXiv2025

Versatile ultrafast single-shot imaging

Ultrafast single-shot imaging techniques now reach frame rates of tens of tera-frame-per-second (Tfps) and long sequence depths but are often too complex for large-scale use, both in terms of image acquisition and reconstruction. We propose an extremely simple yet high-performance method that leverages the capabilities of two prominent technologies: acousto-optical pulse shaping and light-field based hyperspectral imaging. We demonstrate the capabilities of the technique by capturing laser-induced phenomena at frame rates on par with the state-of-the-art, and with the potential to reach the peta-frame-per-second, while keeping a versatile setup that is easily adaptable to various input pulse shapes and dynamic events. Furthermore, an extra degree of freedom is added to the system through the use of digital in-line holography on the single-shot motion pictures. The agility and performance of this technique could then open up new horizons for single-shot imaging techniques, making them accessible to a wider community.

physics.optics↗

arXiv2021

Acousto-optically driven single-shot ultrafast optical imaging

Driven by many applications in a wide span of scientific fields, a myriad of advanced ultrafastimaging techniques have emerged in the last decade, featuring record-high imaging speeds abovea trillion-frame-per-second with long sequence depths. Although bringing remarkable insights invarious ultrafast phenomena, their application out of a laboratory environment is however limitedin most cases, either by the cost, complexity of operation or by an heavy data processing. We thenreport a flexible single-shot imaging technique combining sequentially-timed all-optical mappingphotography (STAMP) with acousto-optics programmable dispersive filtering. The full controlover the acquisition parameters is enabled via the spectro-temporal tailoring of the imaging pulsesin an electrically-driven spectral phase and amplitude shaper in which the pulse shaping in boththe temporal and spectral domains is controlled through the interaction of the light field with anacoustic wave. Here, contrary to most single-shot techniques, the frame rate, exposure time and frameintensities can be independently adjusted in a wide range of pulse durations and chirp values, makingthe system remarkably versatile and user-friendly. The imaging speed of the system as well as itsflexibility are validated by visualizing ultrashort events on both the picosecond and nanosecond timescales. With the perspective of real-world applications and to achieve the highest technical simplicity,we eventually demonstrate its lensless operation based on digital in-line holography. The virtues andlimitations as well as the potential improvements of this on-demand ultrafast imaging method arecritically discussed.

physics.optics↗

arXiv2004

Stability calculations for the ytterbium-doped fiber laser passively mode-locked through nonlinear polarization rotation

We investigate theoretically a fiber laser passively mode-locked with nonlinear polarization rotation. A unidirectional ring cavity is considered with a polarizer placed between two sets of a halfwave plate and a quarterwave plate. A master equation is derived and the stability of the continuous and mode-locked solutions is studied. In particular, the effect of the orientation of the four phase plates and of the polarizer on the mode-locking regime is investigated.

physics.optics↗

arXiv2004

Experimental and theoretical study of the passively mode-locked Ytterbium-doped double-clad fiber laser

We consider an Yb-doped double-clad fiber laser in a unidirectional ring cavity containing a polarizer placed between two half-wave plates. Depending on the orientation of the phase plates, the laser operates in continuous, Q-switch, mode-lock or unstable self-pulsing regime. An experimental study of the stability of the mode locking regime is realized versus the orientation of the half-wave plates. A model for the stability of self-mode-locking and cw operation is developed starting from two coupled nonlinear Schrodinger equations in a gain medium. The model is reduced to a master equation in which the coefficients are explicitly dependent on the orientation angles of the phase plates. Analytical solutions are given together with their stability versus the angles.

nlin.PS↗