Extending the supercontinuum spectrum down to 200 nm with few-cycle pulses (original) (raw)
Related papers
2006
We report new experimental and numerical results on supercontinuum generation at ultraviolet/visible wavelengths produced by the propagation of infrared femtosecond laser pulses in air. Spectral broadening is shown to similarly affect single filaments over laboratory distance scales, as well as broad beams over longrange propagation distances. Numerical simulations display evidence of the crucial role of third harmonic generation in the build-up of UV-visible wavelengths, by comparison with current single-envelope models including chromatic dispersion and self-steepening.
Spectral extent and pulse shape of the supercontinuum for ultrashort laser pulse
IEEE Journal of Quantum Electronics, 1986
The pulse shape and the generated supercontinuum spectral distribution associated with the propagation of an ultrashort intense pulse in a cubic (@') nonlinear medium are obtained by solving the electromagnetic field wave equation using the method of multiple scales. New forms for the set of quasi-linear partial differential equations describing the system, pulse distortion, and the spectral extent of the supercontinuum are the focus of this paper. S I. INTRODUCTION UPERCONTINUUM generation is the production of nearly white continuous spectrum by propagating picosecond and subpicosecond laser pulses through nonlinear media. Alfano and Shapiro [ l ] were the first to experimentally observe this phenomenon more than 15 years ago. They and others [2] used this superbroadening as a means to produce ultrashort pulses in the spectral range from ultraviolet to infrared. The shape, fine structure, and extent of the spectrum produced are functions of the nonlinear index of refraction of the medium, the shape, wavelength, duration, intensity, and phase modulation of the pump laser pulse, and the interaction length of the pulse in the medium. Typically, the observed broadened spectrum consists of larger frequency extent towards the blue than the red by factors of approximately two, a feature commonly referred to as spectral asymmetry. This coherent and ultrafast superbroad frequency band has been mainly used as a spectral tool for time-resolved absorption spectroscopy [3], [4] and nonlinear optical effects [3], [5]. Recently, new uses in engineering applications [6], such as ranging, 3-D imaging, atmospheric remote sensing, and optical fiber characterization, have been proposed. The supercontinuum was explained either as a result of self-phase modulation (SPM) following self-focusing and optical breakdown [7] or as a result of a four-wave parametric process [8]. The asymmetry in the Stokes and anti-Stokes regions was attributed to contributions from plasmas and/or the time response of the nonlinear index of refraction. Recent experiments [9] suggest, however, that the supercontinuum can be observed in experimental conditions where self-focusing and optical breakdown are ab-Manuscript received April 10, 1985.
Supercontinuum generation of ultrashort laser pulses in air at different central wavelengths
2007
Supercontinuum generation by femtosecond filaments in air is investigated for different laser wavelengths ranging from ultraviolet to infrared. Particular attention is paid on the role of third-harmonic generation and temporal steepening effects, which enlarge the blue part of the spectrum. A unidirectional pulse propagation model and nonlinear evolution equations are numerically integrated and their results are compared. Apart from the choice of the central wavelength, we emphasize the importance of the clamped intensity reached by self-guided pulses, together with their temporal duration and propagation length as key players acting on both supercontinuum generation of the pump wave and emergence of the third harmonic. Maximal broadening is observed for large wavelengths and long filamentation ranges. Ó 2007 Published by Elsevier B.V.
2020
This document provides supplementary information to "Ultraviolet-to-millimeter-band supercontinua driven by ultrashort mid-infrared laser pulses," https://doi.org/10.1364/OPTICA.7.000015, offering an expanded description of the methods and models used in our work to analyze and understand UV-to-mm-band supercontinua driven by ultrashort, high-peak-power mid-infrared laser pulses. Technical details of the analysis of phase-matching effects in multidecade supercontinuum generation by mid-infrared laser pulses are also provided.
Backward supercontinuum emission from a filament generated by ultrashort laser pulses in air
Optics Letters, 2001
Backward emission of the supercontinuum from a light filament induced by high-intensity femtosecond laser pulses propagating in air has been observed to be enhanced compared with linear Rayleigh-Mie scattering. This enhancement is interpreted as a nonlinear scattering process onto longitudinal refractive-index changes induced by the laser pulse itself. The spectral dependence of the supercontinuum angular distribution is also investigated.
Supercontinuum Emission from Water using 40 fs Pulses in the External Tight Focusing Limit
2011
From the initial observation of self-channeling of high-peak power femtosecond (fs) laser pulses in air, propagation of intense ultrashort laser pulses in different media has become one of the most investigated research areas. The supercontinuum emission (SCE), a spectral manifestation of the spatio-temporal modifications experienced by a propagating ultrashort laser pulse in a nonlinear medium, has many practical applications. However, the extent of blue shift of SCE is reported to be constant due to the phenomenon of "intensity clamping". To further explore the recently observed regime of filamentation without intensity clamping, we measured the evolution of spectral blue shift of SCE resulting from the propagation of fs pulses (800 nm, 40 fs, 1 kHz) in distilled water under different focusing geometries. The efficiency of SCE from tight focusing (f/6) geometry was always higher than the loose focusing (f/12) geometry for both linear and circular polarized pulses. The blue edge of the SCE spectrum (λ min) was found to be blue shifted for f/6 focusing conditions compared to f/12 focusing geometry. The lower bound of the intensity deposited in the medium measured from the self-emission from the filament demonstrated the existence of intensities ~ 6 ×10 13 Wcm-2 , far beyond the clamping intensities achieved erstwhile.
Dramatic enhancement of supercontinuum generation in elliptically-polarized laser filaments
Scientific Reports, 2016
Broadband laser sources based on supercontinuum generation in femtosecond laser filamentation have enabled applications from stand-off sensing and spectroscopy to the generation and self-compression of high-energy few-cycle pulses. Filamentation relies on the dynamic balance between self-focusing and plasma defocusing – mediated by the Kerr nonlinearity and multiphoton or tunnel ionization, respectively. The filament properties, including the supercontinuum generation, are therefore highly sensitive to the properties of both the laser source and the propagation medium. Here, we report the anomalous spectral broadening of the supercontinuum for filamentation in molecular gases, which is observed for specific elliptical polarization states of the input laser pulse. The resulting spectrum is accompanied by a modification of the supercontinuum polarization state and a lengthening of the filament plasma column. Our experimental results and accompanying simulations suggest that rotational...
Multi-octave supercontinuum generation from mid-infrared filamentation in a bulk crystal
Nature Communications, 2012
In supercontinuum generation, various propagation effects combine to produce a dramatic spectral broadening of intense ultrashort optical pulses. With a host of applications, supercontinuum sources are often required to possess a range of properties such as spectral coverage from the ultraviolet across the visible and into the infrared, shot-to-shot repeatability, high spectral energy density and an absence of complicated pulse splitting. Here we present an all-in-one solution, the first supercontinuum in a bulk homogeneous material extending from 450 nm into the mid-infrared. The spectrum spans 3.3 octaves and carries high spectral energy density (2 pJ nm − 1 -10 nJ nm − 1 ), and the generation process has high shot-to-shot reproducibility and preserves the carrier-to-envelope phase. Our method, based on filamentation of femtosecond mid-infrared pulses in the anomalous dispersion regime, allows for compact new supercontinuum sources.
JETP Letters, 2008
Nonlinear-optical spatiotemporal transformation of high-intensity ultrashort field waveforms in ionizing gases gives rise to the generation of radiation with a broad continuous spectrum . This phenomenon, known as white-light, or supercontinuum, generation suggests interesting options for the remote sensing of the atmosphere [8], the creation of novel broadband light sources , and the development of new strategies for the generation of ultrashort pulses with a stabilized carrier-envelope phase . Supercontinuum generation by few-cycle light pulses is accompanied by intriguing nonlinear-optical effects and reveals unique spatiotemporal dynamics of broadband optical signals .