Harmonic generation in solids with direct fiber laser pumping

Lee, Kevin F.; Ding, Xiaoyan; Hammond, T. J.; Fermann, M. E.; Vampa, Giulio; Corkum, P. B.

doi:10.1364/ol.42.001113

Cited by 32 publications

(22 citation statements)

References 12 publications

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“…Consequently, HHG in solids is being extensively explored both experimentally and theoretically. Experiments using low repetition rate laser sources as pump have demonstrated HHG in different bulk crystals [8][9][10][11] and 2D materials [12][13][14] and the first high repetition rate generation at 70-80 MHz has recently been reported in sapphire [15][16][17]. Based on dynamical Bloch oscillations [4,18], non-perturbative generation of HHG in solids is usually explained by interband and intraband transitions of the electrons inside the band-structure of solids as they interact with the incident laser field as bulk processes [10,11,19].…”

Section: Introductionmentioning

confidence: 99%

Non-perturbative generation of DUV/VUV harmonics from crystal surfaces at 108 MHz repetition rate

Seres¹,

Seres²,

Serrat³

et al. 2018

Opt. Express

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We demonstrate non-perturbative 3rd (267 nm) and 5th (160 nm) harmonic generation in solids from a Ti:sapphire frequency comb (800 nm) at 108 MHz repetition rate. The experiments show that non-perturbative low harmonics are dominantly generated on the surface and on the interface between solids, and that they are not produced by bulk processes from the near-surface layer of the material. Measurements reveal that due to the lack of phase matching, the generated harmonics in bulk are suppressed by orders of magnitude compared to the signal generated on the surface. Our results pave the way for the development of all-solid-state high repetition rate harmonic sources for vacuum ultraviolet spectroscopy and high precision frequency comb metrology.

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Section: Introductionmentioning

confidence: 99%

Non-perturbative generation of DUV/VUV harmonics from crystal surfaces at 108 MHz repetition rate

Seres¹,

Seres²,

Serrat³

et al. 2018

Opt. Express

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“…The cutoff energy of HHG is around Ip+3.17Up (Ip is the ionization potential, and Up=A0 2 /4 is the ponderomotive energy). The HHG from bulk crystals has been reported recently [4,5] as the development of long-wavelength lasers. It is quite different from the HHG from gases.…”

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confidence: 99%

Nonadiabatic redshifts in high-order harmonic generation from solids

2017

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We studied the multi-plateau high-order harmonic generation (HHG) from solids numerically. It is found that the HHG spectrum in the second or higher plateau is redshifted in short laser pulses due to the nonadiabatic effect. The corresponding FWHMs also increase, suggesting the step-by-step excitation process of higher conduction bands in the HHG process. Even order harmonics in the higher plateaus of HHG are present due to the break of symmetry in the k space. It may stimulate related experimental work. High-order harmonic generation (HHG) from gases has been well studied. It has been used to generate attosecond laser pulses [1,2]. It is described by the three-step model [3]. The cutoff energy of HHG is around Ip+3.17Up (Ip is the ionization potential, and Up=A0 2 /4 is the ponderomotive energy). The HHG from bulk crystals has been reported recently [4,5] as the development of long-wavelength lasers. It is quite different from the HHG from gases. The cutoff energy of solid HHG depends on the amplitude of the laser field linearly [4]. It also exhibits multi-plateau structure [6]. However, the mechanisms of HHG from solids are much debated. Inter-and intra-band transitions [4,7,8] are proposed. Three-step model in the coordinate space [9] and vector k space [10] are investigated. Recently, multi-plateau HHG from solids are studied theoretically [7,8,11] and experimentally. Our theoretical model [10] propose that the multi-plateau structure reflects the population of higher conduction bands which are pumped step by step.In the solid systems, even-order harmonics are measured experimentally. They may come from the interference of HHG trajectories in the different valence bands [12]. It may also come from the Berry phase [13]. In this work, we will present a new mechanism for even-order harmonic generation in symmetric periodic potentials.Redshifts of HHG spectra were predicted in the HHG from gases and plasmas [14][15][16][17][18][19][20]. They originate from delayed emission times of HHG from the excited state, resonate state, or dissociation of molecules. It is a nonadiabatic effect. The feature is that most of the HHG signals are generated from the trailing edge of the laser pulse, where dI/dt<0. The driving force from the laser fields is weaker than the previous cycle. The electrons obtain less energy compared to the previous cycle and redshifts of HHG occur. They have been experimentally confirmed [18,[21][22][23]. It was reported that redshift was observed in the optical absorption of crystals in the presence of an intense mid-infrared laser field [24]. In this letter, we find that redshift also exists in emission of HHG from solids. It is universal. The higher conduction bands are excited step by step. As a result, the HHG process in the higher plateau is delayed compared to ultrafast process in the lower conduction bands. As will be shown next, even the system is symmetric in the coordinate space, the electron motion is not symmetric in the k space. Consequently, redshifts of HHG and even-order harmonics ar...

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“…Although the highest HHG repetition rates have been reported using high-power frequency combs resonantly enhanced in optical cavities, 33,34 their reliability and suitability for time-resolved photoemission have faced skepticism from several authors 8,30,35 . Instead, there has been great investment in other approaches including HHG from high-power Ti:Sapphire and parametric amplifiers, 35,36 HHG from high power fiber lasers, 37,38 HHG generated within 39 and at the output 40 of thin-disk lasers, HHG from solids, 41,42 and HHG in the near-fields of nanostructures 43 . Despite these intense efforts, HHG-based photoemission comparable to that done with tunable synchrotron radiation has not been realized using any platform.…”

Section: Introductionmentioning

confidence: 99%

Ultrafast extreme ultraviolet photoemission without space charge

Corder

Zhao

Bakalis

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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Harmonic generation in solids with direct fiber laser pumping

Cited by 32 publications

References 12 publications

Non-perturbative generation of DUV/VUV harmonics from crystal surfaces at 108 MHz repetition rate

Non-perturbative generation of DUV/VUV harmonics from crystal surfaces at 108 MHz repetition rate

Nonadiabatic redshifts in high-order harmonic generation from solids

Ultrafast extreme ultraviolet photoemission without space charge

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