arXiv subjects

Jean-Pierre Wolf

Publications and source records attributed to Jean-Pierre Wolf.

At least 19 recordsLinked to original sources

arXiv2026

Remote Infrared Absorption Spectroscopy with Undetected Photons

We demonstrate a novel method for remote open-path Fourier-transform infrared spectroscopy with undetected photons. Similar to previous quantum spectroscopy works, a mid-infrared spectrum is reconstructed by detecting a near-infrared radiation only, thus bypassing important limitations of infrared detectors. Our study however relies on the co-propagation of the photon-pair and the pump-laser over the same optical path, which allows the probing of the open atmosphere over long distances. By sending the photons over unprecedented distances of up-to 43.4m in the outdoor atmosphere, we were able to detect butane released in the open-path, as well as natural atmospheric methane, thus demonstrating the first use of infrared spectroscopy with undetected photons for atmospheric measurements.

quant-ph↗

arXiv2024

Physics and technology of Laser Lightning Control

The recent development of high average, high peak power lasers has revived the effort of using lasers as a potential tool to influence natural lightning. Although impressive, the current progress in laser lightning control technology may only be the beginning of a new area involving a positive feedback between powerful laser development and atmospheric research. In this review paper, we critically evaluate the past, present and future of Laser Lightning Control (LLC), considering both its technological and scientific significance in atmospheric research.

eess.SY↗

arXiv2024

Open-Path Detection of Organic Vapors via Quantum Infrared Spectroscopy

In recent years, quantum Fourier transform infrared (QFTIR) spectroscopy emerged as an alternative to conventional spectroscopy in the mid-infrared region of the spectrum. By harnessing induced coherence and spectral entanglement, QFTIR offers promising potential for the practical detection of organic gasses. However, little research was conducted to bring QFTIR spectrometers closer to domestic or in-field usage. In this work, we present the first use of a QFTIR spectrometer for open-path detection of multiple interfering organic gases in ambient air. The accurate identification of mixtures of acetone, methanol, and ethanol vapors is demonstrated with a QFTIR spectrometer. We achieved this breakthrough by building a nonlinear Michelson interferometer with 1.7m-long arms to increase the absorption length, coupled with analysis techniques from differential absorption spectroscopy. The evolution of different gasses' concentrations in ambient air was measured through time. These results constitute the first use-case of a QFTIR spectrometer as a detector of organic gasses, and thus represent an important milestone towards the development of such detectors in practical situations.

quant-ph↗

arXiv2023

High-power sub-picosecond filamentation at 1.03 μm with high repetition rates between 10 and 100 kHz

Filamentation has extensively been explored and is well understood at repetition rates <1 kHz due to the typical availability of multi-mJ laser systems at a moderate average power. The advent of high-power Yb-lasers opened new possibilities for filamentation research. However, so far, high average power Yb systems have mostly been explored to increase the driving pulse energy to several hundreds of mJ and not at significantly higher repetition rates. In this paper, we study, for the first time, long filaments at unprecedented high repetition rates of 10, 40, and 100 kHz using a 500-W Yb-doped thin-disk amplifier driver operating with sub-700 fs pulses. We compare the filament length, density hole, and fluorescence at a constant peak power but different repetition rates and find a strong dependence on filament length and density depletion with repetition rate. Our analysis reveals the emergence of a significant stationary density depletion at repetition rates of 40 and 100 kHz. The corresponding reduction in the breakdown threshold by increasing the laser repetition rate observed in our study signifies a promising avenue for enhancing the efficiency and reliability of electric discharge triggering in various scenarios. Using capacitive plasma probe measurements, we address the limitations of fluorescence imaging-based measurements and demonstrate a systematic underestimation of filament length. This work contributes to a deeper understanding of the interplay between laser repetition rates, filamentation, and heat-driven density depletion effects from high-repetition-rate high-power laser systems and will contribute to guiding future research, making use of filaments at high repetition rates.

physics.optics↗

arXiv2023

Laser-guided lightning

Electric currents circulating between charged clouds and the earth surface during lightning discharges are responsible for considerable damages and casualties. It is therefore important to develop better protection methods in addition to the traditional Franklin rod. Here we present the first demonstration that filaments formed by short and intense laser pulses can guide lightning discharges over considerable distances. We believe that this experimental breakthrough will lead to progress in lightning protection and lightning physics. An experimental campaign was carried out on the Säntis Mountain in Northeastern Switzerland during the Summer of 2021 with a high repetition rate terawatt laser. The guiding of an upward negative lightning leader over a distance of 50 m was recorded by two separate high-speed cameras. The guiding of negative lightning leaders by laser filaments was corroborated in three other instances by VHF interferometric measurements, and the number of X-ray bursts detected during guided lightning events was significantly increased. While this research field has been very active for more than 20 years with many research groups around the world working to achieve this goal, this result demonstrates lightning guiding by lasers, which may lead to the development of a laser lightning rod. This work paves the way for new atmospheric applications of ultrashort lasers and represents a significant step forward in the development of a laser based lightning protection for airports, launchpads or large infrastructures.

physics.optics↗

arXiv2022

Optimal laser pulse energy partitioning for air ionization

We investigate the pulse partitioning of a 6.3 mJ, 450 fs pulse at 1030 nm to produce plasma channels. At such moderate energies, splitting the energy into several sub-pulses reduces the ionization efficiency and thus does not extend the plasma lifetime. We numerically show that when sufficient energy to produce multifilamentation is available, splitting the pulse temporally in a pulse train increases the gas temperature compared to a filament bundle of the same energy. This could improve the mean free path of the free electrons, therefore enhancing the efficiency of discharge triggering.

physics.plasm-ph↗

arXiv2022

Opto-mechanical expulsion of individual micro-particles by laser-induced shockwave in air

It was recently demonstrated that laser filamentation was able to generate an optically transparent channel through cloud and fog for free-space optical communications applications. However, no quantitative measurement of the interaction between the laser-induced shockwave and the aerosol particles was carried out so far, leaving the precise nature of the clearing mechanism up for discussion. A critical question was the maximum distance at which the filament could still act on the aerosol particle. Distances widely exceeding the filament diameter and its energy reservoir exclude other potential clearing effects like shattering or explosion by direct exposure to the laser. Here, we quantify the force exerted by the shockwave on a single aerosol microparticle. The force is measured by observing the ejection and displacement of the particle when trapped in an optical tweezer. We demonstrate that even for distances ranging from 1.5 mm to 5.5 mm away from the filament, thus widely exceeding the filamentary region, an acoustic force of 500 pN to 8 nN (depending on the initial laser power) acts on the aerosol particle and expels it away from the optical trap.

physics.optics↗

arXiv2021

Temperature Measurements of Liquid Flat Jets in Vacuum

Sub-μm thin samples are essential for spectroscopic purposes. The development of flat micro-jets enabled novel spectroscopic and scattering methods for investigating molecular systems in the liquid phase. However characterization of the temperature of these ultra-thin liquid sheets in vacuum has not been systematically investigated. Here we present a comprehensive temperature characterization of two methods producing sub-micron flatjets, using optical Raman spectroscopy: colliding of two cylindrical jets and a cylindrical jet compressed by a high pressure gas. Our results reveal the dependence of the cooling rate on the material properties and the source characteristics, i.e. nozzle orifice size,flowrate, pressure. We show that materials with higher vapour pressures exhibit faster cooling rates which is illustrated by comparing the temperature profile of liquid water and ethanol flatjets. In a sub-μm liquid sheet, the temperature of the water sample reaches around 268 K and the ethanol around 253 K.

physics.chem-ph↗

arXiv2020

Molecular Quantum Wakes for Clearing Fog

High intensity laser filamentation in air has recently demonstrated that, through plasma generation and its associated shockwave, fog can be cleared around the beam, leaving an optically transparent path to transmit light. However, for practical applications like free-space optical communication (FSO), channels of multi-centimeter diameters over kilometer ranges are required, which is extremely challenging for a plasma based method. Here we report a radically different approach, based on quantum control. We demonstrate that fog clearing can also be achieved by producing molecular quantum wakes in air, and that neither plasma generation nor filamentation are required. The effect is clearly associated with the rephasing time of the rotational wave packet in N2.Pump excitation provided in the form of resonant trains of 8 pulses separated by the revival time are able to transmit optical data through fog with initial extinction as much as -6 dB.

physics.optics↗

arXiv2019

Ab-initio calculations of laser-atom interactions reveal harmonics feedback during macroscopic propagation

We couple the full 3D ab initio quantum evolution of the light pulse polarization in interaction with an atom with a propagation model to simulate the propagation of ultrashort laser pulses over macroscopic dimensions, in the presence of self-generated harmonics up to order 11. We evidence a clear feedback of the generated harmonics on propagation, with an influence on the ionization probability as well as the yield of the harmonic generation itself.

physics.optics↗

arXiv2019

HV discharges triggered by dual- and triple-frequency laser filaments

We study the use of frequency upconversion schemes of near-IR picosecond laser pulses and compare their ability to guide and trigger electric discharges through filamentation in air. Upconversion, such as Second Harmonic Generation, is favorable for triggering electric discharges for given amount of available laser energy, even taking into account the losses inherent to frequency conversion. We focus on the practical question of optimizing the use of energy from a given available laser system and the potential advantage to use frequency conversion schemes.

physics.plasm-ph↗

arXiv2018

Amplification of intense light fields by nearly free electrons

Light can be used to modify and control properties of media, as in the case of electromagnetically induced transparency or, more recently, for the generation of slow light or bright coherent XUV and X-ray radiation. Particularly unusual states of matter can be created by light fields with strengths comparable to the Coulomb field that binds valence electrons in atoms, leading to nearly-free electrons oscillating in the laser field and yet still loosely bound to the core [1,2]. These are known as Kramers-Henneberger states [3], a specific example of laser-dressed states [2]. Here, we demonstrate that these states arise not only in isolated atoms [4,5], but also in rare gases, at and above atmospheric pressure, where they can act as a gain medium during laser filamentation. Using shaped laser pulses, gain in these states is achieved within just a few cycles of the guided field. The corresponding lasing emission is a signature of population inversion in these states and of their stability against ionization. Our work demonstrates that these unusual states of neutral atoms can be exploited to create a general ultrafast gain mechanism during laser filamentation.

physics.optics↗

arXiv2018

Free space laser telecommunication through fog

Atmospheric clearness is a key issue for free space optical communications (FSO). We present the first active method to achieve FSO through clouds and fog, using ultrashort high intensity laser filaments. The laser filaments opto-mechanically expel the droplets out of the beam and create a cleared channel for transmitting high bit rate telecom data at 1.55 microns. The low energy required for the process allows considering applications to Earth-satellite FSO and secure ground based optical communication, with classical or quantum protocols.

physics.optics↗

arXiv2018

Modifications of filament spectra by shaped octave-spanning laser pulses

In this paper we examine the spectral changes in a white light laser filament due to different pulse shapes generated by a pulse shaping setup. We particularly explore how the properties of the filament spectra can be controlled by parametrically tailored white light pulses. The experiments are carried out in a gas cell with up to 9 bar of argon. Plasma generation and self-phase modulation strongly affect the pulse in the spectral and temporal domain. By exploiting these effects we show that the pulse spectrum can be modified in a desired way by either using second order parametric chirp functions to shift the filament spectrum to higher or lower wavelengths, or by optimizing pulse shapes with a genetic algorithm to generate more complex filament spectra. This paper is one of the first examples of the application of complex, parametrically shaped white light pulses.

physics.optics↗

arXiv2018

Maximizing energy deposition by shaping few-cycle laser pulses

We experimentally investigate the impact of pulse shape on the dynamics of laser-generated plasma in rare gases. Fast-rising triangular pulses with a slower decay lead to early ionization of the air and depose energy more efficiently than their temporally reversed counterparts. As a result, in both argon and krypton, the induced shockwave as well as the plasma luminescence are stronger. This is due to an earlier availability of free electrons to undergo inverse Bremsstrahlung on the pulse trailing edge. Our results illustrate the ability of adequately tailored pulse shapes to optimize the energy deposition in gas plasmas.

physics.optics↗

arXiv2018

Bismuth Ferrite Dielectric Nanoparticles Excited at Telecom Wavelengths as Multicolor Sources by Second, Third, and Fourth Harmonic Generation

We demonstrate the simultaneous generation of second, third, and fourth harmonic from a single dielectric Bismuth Ferrite nanoparticle excited by a telecom fiber laser at 1560 nm. We first characterize the signals associated with different nonlinear orders in terms of spectrum, excitation intensity dependence, and relative signal strengths. Successively, on the basis of the polarization-resolved emission curves of the three harmonics, we discuss the interplay of susceptibility tensor components at the different orders and we show how polarization can be used as an optical handle to control the relative frequency conversion properties.

physics.optics↗

arXiv2017

HV discharge acceleration by sequences of UV laser filaments with visible and near-infrared pulses

We investigate the triggering and guiding of DC high-voltage discharges over a distance of 37 cm by filaments produced by ultraviolet (266 nm) laser pulses of 200 ps duration. The latter reduce the breakdown electric field by half and allow up to 80% discharge probability in an electric field of 920 kV/m. This high efficiency is not further increased by adding nanosecond pulses in the Joule range at 532 nm and 1064 nm. However, the latter statistically increases the guiding length, thereby accelerating the discharge by a factor of 2. This effect is due both to photodetachment and to the heating of the plasma channel, that increases the efficiency of avalanche ionization and reduces electron attachment and recombination.

physics.optics↗

arXiv2017

Time-resolved monitoring of polycyclic aromatic hydrocarbons adsorbed on atmospheric particles

Real-time monitoring of individual particles from atmospheric aerosols was performed by means of a specifically developed single-particle fluorescence spectrometer (SPFS). The observed fluorescence was assigned to particles bearing polycyclic aromatic hydrocarbons (PAH). This assignment was supported by an intercomparison with classical speciation on filters followed by gas chromatography-mass spectrometry (GC-MS) analysis. As compared with daily-averaged data, our time resolved approach provided information about the physicochemical dynamics of the particles. In particular, distinctions were made between background emissions related to heating, and traffic peaks during rush hours. Also, the evolution of the peak fluorescence wavelength provided an indication of the aging of the particles during the day.

physics.ao-ph↗