Maximizing the brilliance of high-order harmonics in a gas jet

Lohbreier, Jan; Eyring, Stefan; Spitzenpfeil, Robert; Kern, Christian; Weger, Matthias; Spielmann, Christian

doi:10.1088/1367-2630/11/2/023016

Cited by 10 publications

(5 citation statements)

References 24 publications

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“…These modified laser pulses are then focused (f = 300 mm, f /# = 15) into the interaction region to a diameter of roughly 40 µm, resulting in peak intensities of approximately 2 × 10 15 W cm −2 (ref. 29). The interaction region consists of a nickel tube (2 mm diameter) sealed at the end and squeezed (d ∼ 1 mm) to a flat surface facing the laser beam.…”

Section: Methodsmentioning

confidence: 99%

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Strong-field physics with singular light beams

et al. 2012

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Light beams carrying a point singularity with a screw-type phase distribution are associated with an optical vortex. The corresponding momentum flow leads to an orbital angular momentum of the photons 1-3 . The study of optical vortices has led to applications such as particle micro-manipulation 4,5 , imaging 6 , interferometry 7 , quantum information 8 and highresolution microscopy and lithography 9 . Recent analyses showed that transitions forbidden by selection rules seem to be allowed when using optical vortex beams 10 . To exploit these intriguing new applications, it is often necessary to shorten the wavelength by nonlinear frequency conversion. However, during the conversion the optical vortices tend to break up 11-13 . Here we show that optical vortices can be generated in the extreme ultraviolet (XUV) region using high-harmonic generation 14,15 . The singularity impressed on the fundamental beam survives the highly nonlinear process. Vortices in the XUV region have the same phase distribution as the driving field, which is in contradiction to previous findings 16 , where multiplication of the momentum by the harmonic order is expected. This approach opens the way for several applications based on vortex beams in the XUV region.Places where physical quantities become infinite or change abruptly are called singularities. The presence of phase dislocations (singularities) in the wavefront of a light beam determines both the phase and intensity structure around them. As the phase becomes indeterminate at singularities, both the real and the imaginary parts of the field amplitude (that is, also the field intensity) vanish. The characteristic helical phase profiles of optical vortices are described by exp(imθ) multipliers, where θ is the azimuthal coordinate and the integer number m is their topological charge, also called dislocation strength or winding number.Recalling the fact that in free space the Poynting vector gives the momentum flow, for helical phase fronts the Poynting vector has an azimuthal component that produces an orbital angular momentum parallel to the axis of the beam. The momentum circulates around the beam axis, so such beams are said to contain an optical vortex. As has been shown 1-3 , an m-fold charged optical vortex beam carries an orbital angular momentum of mh per photon independent of the spin angular momentum (that is, the polarization state). It was shown that transitions that are forbidden by known selection rules in the electric and magnetic dipole approximation seem to be allowed when using optical vortex beams 10 . This provides a new degree of freedom in the spectroscopy of forbidden transitions. Multi-coloured optical vortices can be generated through a nonlinear frequency-conversion process such as second-harmonic generation 16 or four-wave mixing, which is an important process in the white-light vortex generation. However, as predicted in ref. 11 and observed in ref. 12, vortex breakup in self-focusing nonlinear media is an important issue for supercontinuum vortex genera...

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Section: Methodsmentioning

confidence: 99%

“…3) is described elsewhere 29 . The Hartmann pattern obtained from illumination of the mask with a Gaussian fundamental mode was used for calibration to remove intrinsic aberrations present in the XUV beam.…”

Section: Methodsmentioning

confidence: 99%

Strong-field physics with singular light beams

et al. 2012

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“…Although high harmonic generation has the potential candidate provide bright short optical pulses, it suffers from its low conversion efficiency [28,29]. Optimization of harmonic generation yield has been studied by several researchers [12][13][14][15][30][31][32][33]. The brightness of such a light source is a benchmark for studying light-matter interaction.…”

Section: Introductionmentioning

confidence: 99%

N2 Molekülünden ve Bunun Ne Gazı ile Karışımından Sub-terawatt Lazer Sistemi kullanılarak Uyumlu XUV Radyasyonu Üretilmesi

SAYRAÇ

2024

Düzce Üniversitesi Bilim Ve Teknoloji Dergisi

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High harmonic generation (HHG) in pure nitrogen (N2) and its mixture with neon (Ne) gas was produced. The external laser field producing 6mJ optical pulse energy with 50fs pulse duration at 10Hz repetition rate was focused into a gas jet producing high harmonics. The N2 and Ne gas have different ionization potentials. The strong harmonic signal in pure N2 was produced, and a weak harmonic signal in a mixture of N2-Ne was generated compared to that in pure N2. The increase of Ne contribution in the N2-Ne mixture resulted in a decrease in harmonic signal. Harmonic signal increase and decrease were observed for different N2:Ne ratios. The harmonic generation mechanism was discussed in that the ionization of Ne is difficult compared to N2, and the neutral Ne atom leads to neutral atomic dispersion (phase mismatch), so the harmonic yield decreases.

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“…[13]. Due to the rather low conversion efficiency of the HHG process [14,15], the optimization of HHG in terms of brilliance-or number of photons per time interval imping-ing on a sample-has been an ongoing topic in the community [16][17][18][19]. The brilliance, or brightness, of a light source is the standard when comparing photon-producing elements, and is the benchmark especially when researching light-matter interactions with low rates or cross-sections.…”

Section: Introductionmentioning

confidence: 99%

Limitations of Extreme Nonlinear Ultrafast Nanophotonics

2015

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High-harmonic generation (HHG) has been established as an indispensable tool in optical spectroscopy. This effect arises for instance upon illumination of a noble gas with sub-picosecond laser pulses at focussed intensities significantly greater than 10 12 W/cm 2 . HHG provides a coherent light source in the extreme ultraviolet (XUV) spectral region, which is of importance in inner shell photo ionization of many atoms and molecules. Additionally, it intrinsically features light fields with unique temporal properties. Even in its simplest realization, XUV bursts of sub-femtosecond pulse lengths are released. More sophisticated schemes open the path to attosecond physics by offering single pulses of less than 100 attoseconds duration.Resonant optical antennas are important tools for coupling and enhancing electromagnetic fields on scales below their free-space wavelength. In a special application, placing field-enhancing plasmonic nano antennas at the interaction site of an HHG experiment has been claimed to boost local laser field strengths, from insufficient initial intensities to sufficient values. This was achieved with the use of arrays of bow-tie-shaped antennas of ∼ 100 nm in length. However, the feasibility of this concept depends on the vulnerability of these nano-antennas to the still intense driving laser light. We show, by looking at a set of exemplary metallic structures, that the threshold fluence F th of laser-induced damage (LID) is a greatly limiting factor for the proposed and tested schemes along these lines. We present our findings in the context of work done by other groups, giving an assessment of the feasibility and effectiveness of the proposed scheme.

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Maximizing the brilliance of high-order harmonics in a gas jet

Cited by 10 publications

References 24 publications

Strong-field physics with singular light beams

Strong-field physics with singular light beams

N2 Molekülünden ve Bunun Ne Gazı ile Karışımından Sub-terawatt Lazer Sistemi kullanılarak Uyumlu XUV Radyasyonu Üretilmesi

Limitations of Extreme Nonlinear Ultrafast Nanophotonics

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