Femtosecond Enhancement Cavities in the Nonlinear Regime

Holzberger, Simon; Lilienfein, Nikolai; Carstens, Henning; Saule, Tobias; Högner, Maximilian; Lücking, Fabian; Trubetskov, Michael K.; Pervak, Vladimir; Eidam, Tino; Limpert, Jens; Tünnermann, Andreas; Fill, Ernst E.; Krausz, Ferenc; Pupeza, Ioachim

doi:10.1103/physrevlett.115.023902

“…Just a few years ago, femtosecond ECs have been used for the first frequency comb spectroscopy experiments in the vacuum ultraviolet spectral region [14,15]. Owing to recent progress concerning advanced cavity designs [12,16], the quantitative understanding of the intracavity gas target nonlinearity [17][18][19], and thanks to scaling the bandwidth of ECs [20] and of phase-stable, high-power seeding laser systems [21][22][23], it seems feasible as from today's point of view to extend this technology to application in attosecond physics. However, state-of-the-art dielectric multilayer optics cannot cover the bandwidth necessary for single-cycle near-infrared pulses [20], which would enable the direct generation of IAPs in ECs.…”

Section: Introductionmentioning

confidence: 99%

Generation of isolated attosecond pulses with enhancement cavities—a theoretical study

Högner

¹

,

Toşa

²

,

Pupeza

³

2017

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The generation of extreme-ultraviolet (XUV) isolated attosecond pulses (IAPs) has enabled experimental access to the fastest phenomena in nature observed so far, namely the dynamics of electrons in atoms, molecules and solids. However, nowadays the highest repetition rates at which IAPs can be generated lies in the kHz range. This represents a rather severe restriction for numerous experiments involving the detection of charged particles, where the desired number of generated particles per shot is limited by space charge effects to ideally one. Here, we present a theoretical study on the possibility of efficiently producing IAPs at multi- MHz repetition rates via cavity-enhanced high-harmonic generation (HHG). To this end, we assume parameters of state-of-the-art Yb-based femtosecond laser technology to evaluate several time-gating methods which could generate IAPs in enhancement cavities. We identify polarization gating and a new method, employing non-collinear optical gating in a tailored transverse cavity mode, as suitable candidates and analyze these via extensive numerical modeling. The latter, which we dub transverse mode gating (TMG) promises the highest efficiency and robustness. Assuming 0.7 μ J , 5-cycle pulses from the seeding laser and a state-of-the-art enhancement cavity, we show that TMG bares the potential to generate IAPs with photon energies around 100 eV and a photon flux of at least 10 8 photons s − 1 at repetition rates of 10 MHz and higher. This result reveals a roadmap towards a dramatic decrease in measurement time (and, equivalently, an increase in the signal-to-noise ratio) in photoelectron spectroscopy and microscopy. In particular, it paves the way to combining attosecond streaking with photoelectron emission microscopy, affording, for the first time, the spatially and temporally resolved observation of plasmonic fields in nanostructures. Furthermore, it promises the generation of frequency combs with an unprecedented bandwidth for XUV precision spectroscopy.

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“…29,30 Although generating high harmonics in these cavities was originally demonstrated as early as 2005, 106,107 since then through the use of higher power driving lasers and understanding of the intracavity extreme-nonlinear optics [108][109][110][111] the power from cavityenhanced HHG systems has increased by more than 6 orders of magnitude, to more the 100 µW/harmonic (at the gas jet) for 20 eV harmonics generated in xenon. 12,108,110,112,113 FIG.…”

Section: B Cavity-enhanced High-order Harmonic Generation and Extremmentioning

confidence: 99%

High-power ultrafast Yb:fiber laser frequency combs using commercially available components and basic fiber tools

Li

¹

,

Reber

²

,

Corder

³

et al. 2016

Review of Scientific Instruments

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We present a detailed description of the design, construction, and performance of high-power ultrafast Yb:fiber laser frequency combs in operation in our laboratory. We discuss two such laser systems: an 87 MHz, 9 W, 85 fs laser operating at 1060 nm and an 87 MHz, 80 W, 155 fs laser operating at 1035 nm. Both are constructed using low-cost, commercially available components, and can be assembled using only basic tools for cleaving and splicing single-mode fibers. We describe practical methods for achieving and characterizing low-noise single-pulse operation and long-term stability from Yb:fiber oscillators based on nonlinear polarization evolution. Stabilization of the combs using a variety of transducers, including a new method for tuning the carrier-envelope offset frequency, is discussed. High average power is achieved through chirped-pulse amplification in simple fiber amplifiers based on double-clad photonic crystal fibers. We describe the use of these combs in several applications, including ultrasensitive femtosecond time-resolved spectroscopy and cavity-enhanced high-order harmonic generation. C 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license

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“…The plasma phase shifts on the fundamental pulse gate the harmonic emission when they approach ∼ π / q , where q is the harmonic order. However, in CE-HHG, because the power enhancement relies on the constructive interference of the pulse in the cavity with pulses coming from the laser, time-dependent phase shifts are restricted to be less than

2 π / F

, 58 roughly one order of magnitude smaller than the scale relevant for ionization gating. Under these conditions, the emission window is determined by the high harmonic dipole, d q ( t ), and not ionization gating, such that harmonic linewidths significantly narrower than achieved in single-pass HHG systems under their typical operating conditions are expected.…”

Section: Photoemissionmentioning

confidence: 99%

Ultrafast extreme ultraviolet photoemission without space charge

Corder

¹

,

Zhao

²

,

Bakalis

³

et al. 2018

Structural Dynamics

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Time- and Angle-resolved photoelectron spectroscopy from surfaces can be used to record the dynamics of electrons and holes in condensed matter on ultrafast time scales. However, ultrafast photoemission experiments using extreme-ultraviolet (XUV) light have previously been limited by either space-charge effects, low photon flux, or limited tuning range. In this article, we describe XUV photoelectron spectroscopy experiments with up to 5 nA of average sample current using a tunable cavity-enhanced high-harmonic source operating at 88 MHz repetition rate. The source delivers >1011 photons/s in isolated harmonics to the sample over a broad photon energy range from 18 to 37 eV with a spot size of 58 × 100 μm2. From photoelectron spectroscopy data, we place conservative upper limits on the XUV pulse duration and photon energy bandwidth of 93 fs and 65 meV, respectively. The high photocurrent, lack of strong space charge distortions of the photoelectron spectra, and excellent isolation of individual harmonic orders allow us to observe laser-induced modifications of the photoelectron spectra at the 10−4 level, enabling time-resolved XUV photoemission experiments in a qualitatively new regime.

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Femtosecond Enhancement Cavities in the Nonlinear Regime

Cited by 35 publications

References 28 publications

Generation of isolated attosecond pulses with enhancement cavities—a theoretical study

Generation of isolated attosecond pulses with enhancement cavities—a theoretical study

High-power ultrafast Yb:fiber laser frequency combs using commercially available components and basic fiber tools

Ultrafast extreme ultraviolet photoemission without space charge

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