Search

Enhanced high repetition rate coherent extreme ultraviolet (XUV) harmonics represent efficient probe of electron dynamics in atoms, molecules and solids. In this work, we used orthogonally-polarized two-color laser field to generate strong even and odd high order harmonics from molecular gas targets. The dynamics of odd and even harmonics from O2, and N2 gases were investigated by employing single- and two-color laser fields using the fundamental radiation and second harmonic of 1030 nm, 37 fs, 50 kHz pulses. The relative efficiencies of harmonics were analyzed as a function of the thickness of the barium borate crystal used for second harmonic generation. Defocusing-assisted phase matching conditions were achieved in N2 gas for different groups of XUV harmonics.

The wettability behavior of materials is the subject of numerous scientific investigations due to its significance and relevance to wide range of applications. Here we present comparative analysis ...

Molecular adsorbate reactions on nanoparticles play a fundamental role in areas such as nano-photocatalysis, atmospheric, and astrochemistry. They can be induced, enhanced, and controlled by field localization and enhancement on the nanoparticle surface. In particular, the ability to perform highly controlled near-field-mediated reactions is key to deepening our understanding of surface photoactivity on nanosystems. Here, using reaction nanoscopy, we experimentally demonstrate all-optical nanoscopic control of surface reaction yields by tailoring the near fields on nanoparticles with waveform-controlled linear and bicircular two-color laser pulses, respectively. We observe site-selective proton emission from the dissociative ionization of adsorbate molecules on Si O 2 nanoparticles as a function of the polarization and relative phase of the two-color pulses. The angularly resolved close-to-uniform mapping between the surface reaction yields and the measured ion momentum enables the observation and spatial control of molecular reactions on the nanoparticle surface with nanoscopic resolution. The experimental results are modeled and reproduced qualitatively by classical trajectory Monte Carlo simulations. Our work paves the way toward reliable all-optical control of photocatalytic chemical reactions on nanoscale surfaces.

Ultrafast light-induced molecular reactions on aerosolized nanoparticles may elucidate early steps in the photoactivity of nanoparticles with potential impact in fields ranging from chemistry and m...

We synthesize Zn and ZnSe nanoparticles during laser ablation of bulk material in ethanol and analyze them using the Z-scan technique and the generation of high harmonics using a 50 kHz, 40 fs, and 1030 nm laser. The low-order nonlinear absorption and nonlinear refraction coefficients in the colloidal suspensions of the formed nanoparticles were measured using 1030 nm and 515 nm probing laser pulses, respectively. The values of the nonlinear refractive index and nonlinear absorption coefficient of Zn NPs at 1030 nm wavelength were calculated to be γ = − 1.4 × 10 − 13 c m 2 W − 1 and β = 2.7 × 10 − 11 c m W − 1 , respectively. Similarly, in the case of ZnSe NPs, γ = − 4.9 × 10 − 14 c m 2 W − 1 and β = 0.5 × 10 − 11 c m W − 1 , respectively. In the case of 515 nm probing pulses, the corresponding nonlinear optical parameters of Zn NP suspension were calculated to be γ = − 1.7 × 10 − 14 c m 2 W − 1 and β = 1.0 × 10 − 11 c m W − 1 , and for ZnSe NP suspension, the value of β was calculated to be 2.1 × 10 − 11 c m W − 1 . The nonlinear refractive index of this suspension was γ = − 2.4 × 10 − 14 c m 2 W − 1 . We also report the studies of high-order harmonics generation in plasmas containing Zn and ZnSe NPs using single- (1030 nm) and two-color (1030 nm + 515 nm) laser fields. The maximal generated extreme ultraviolet (XUV) harmonics were 33rd (Zn NPs) and 27th (ZnSe NPs) orders. The decrease of the maximal generating harmonic orders was explained using the three-step model. The high brightness of the ninth and 10th harmonics generated in the two-color laser field was obtained due to the resonance properties of Zn NPs. The maximal generated XUV harmonics were the 33rd (Zn nanoparticles) and 27th (ZnSe nanoparticles) orders.

Ultrafast laser ablation of metal surfaces is a common physical process used to generate periodic surface structures with tuneable multifunctionality for various applications in science and technology. In this work, the formation of femtosecond laser-induced periodic surface structures (LIPSSs) is investigated with 50 kHz repetition rate laser of 40 fs pulse duration and a central wavelength ( λ w = 1030 nm ) along with its second ( λ 2 w = 515 nm ) and third ( λ 3 w = 343 nm ) harmonic components. The variation in the LIPSS periodicity is demonstrated by changing the wavelength of the ablating laser pulses. LIPSS with periodicity ∼0.85 μ m at the fundamental ablating pulses, ∼0.42 μ m periodicity at the second harmonic, and ∼0.35 μ m periodicity at the third harmonic were observed. The third harmonic radiation was generated in an air-filament with minimal temporal delay with respect to the fundamental driving pulses to structure Nickel surfaces at ambient conditions. The approach demonstrates the potential for generating very fine LIPSS on materials’ surfaces using the efficient high-order harmonics of an infrared fundamental laser beam.

Regarded as the most important ion in interstellar chemistry, the trihydrogen cation, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm{H}}}_{{{3}}}^{+}$$\end{document}H3+, plays a vital role in the formation of water and many complex organic molecules believed to be responsible for life in our universe. Apart from traditional plasma discharges, recent laboratory studies have focused on forming the trihydrogen cation from large organic molecules during their interactions with intense radiation and charged particles. In contrast, we present results on forming \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm{H}}}_{{{3}}}^{+}$$\end{document}H3+ from bimolecular reactions that involve only an inorganic molecule, namely water, without the presence of any organic molecules to facilitate its formation. This generation of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${{\rm{H}}}_{{{3}}}^{+}$$\end{document}H3+ is enabled by “engineering” a suitable reaction environment comprising water-covered silica nanoparticles exposed to intense, femtosecond laser pulses. Similar, naturally-occurring, environments might exist in astrophysical settings where hydrated nanometer-sized dust particles are impacted by cosmic rays of charged particles or solar wind ions. Our results are a clear manifestation of how aerosolized nanoparticles in intense femtosecond laser fields can serve as a catalysts that enable exotic molecular entities to be produced via non-traditional routes., The H3+ ion plays a key role in interstellar chemistry and can be formed from organic compounds upon interaction with charged particles or radiation. Here the authors demonstrate that H3+ can also be formed from water adsorbed on silica nanoparticles exposed to intense laser pulses, conditions that mimic the impact of charged particles on dust in astrophysical settings.

We analyze vacuum storage-assisted transformation of laser-textured aluminum, copper and stainless steel from hydrophilic to hydrophobic state that occurs only in the case of vacuum pump that uses mineral oils and additives. Energy-dispersive X-ray spectroscopy measurements demonstrate an increase in the carbon-containing components on the metals surface with the increase of the storage time inside the vacuum chamber. The alternative storing of laser-treated hydrophilic samples at the conditions when vacuum was obtained using oil-free pumps did not reveal any change in the wettability properties. Reverse transition from the hydrophobic to the hydrophilic state is achieved by annealing only in oxygen-containing environment. We found that low-temperature annealing of as-prepared laser-textured samples in air did not transform the wettability of the hydrophilic metals.

In high-order harmonic generation in low-dense media, the application of two-colored pump has been shown to enhance odd-order harmonics, as well as the generation of strong even harmonics. Here, we apply this approach to compare high-order harmonic generation from laser-produced plasmas and gases using different mechanisms of harmonic emission enhancement. We generate two-color pump (TCP, 806 nm + 403 nm and 1030 nm + 515 nm) using two nonlinear crystals of different thickness (0.2 and 0.4 mm in the case of experiments with plasmas using 806 nm pump; and 0.1 mm and 0.4 mm in the case of experiments with gases and plasmas using 1030 nm pump) to demonstrate the enhancement of odd and even harmonics in laser-produced plasmas and by applying weak second field (403 or 515 nm) at different overlaps of pump pulses. The high-order harmonic generation in two media using TCP pulses is optimized. We demonstrate the wavelength dependence and the prevailing role of the partial overlap between the two orthogonally polarized waves in laser-produced plasmas and gases over large ratios of the second-order and fundamental photons. Our results are supported by the non-perturbative single atom theory and the interference model simulations.

We demonstrate the formation of permanent and iridescent colors on aluminum, copper, steel, and brass surfaces using femtosecond laser-induced periodic and non-periodic nanostructuring. We show that both the permanent and iridescent colors of the metal surfaces can be erased and re-colored using a second stage of laser processing. A correlation was found between the spectral reflective properties of the laser-processed surfaces and their wettability properties. Transition from superhydrophilic to superhydrophobic response is observed while tailoring the optical reflectance of the metal surfaces. We employ a high power femtosecond fiber laser at 150 kHz repetition rate, which notably reduces the processing time, making this technique attractive for practical applications.

Oil-water separation by super-wetting and selective permeability of membranes for oil or water has great ecological and economic significance. We report on the transition of wettability response, from superhydrophilic underwater-superoleophobic to superhydrophobic-superoleophilic, by nanostructuring stainless steel and copper meshes using ultrashort femtosecond laser pulses. Our approach is environment-friendly, chemical free and, and efficient as it exploits the benefit of aging the processed samples in high vacuum environment. We optimized the laser scanning parameters, mesh pore size and ageing conditions to produce membrane exhibiting extraordinary separation efficiency of 98% for oil-water mixture. A variation in the water and oil contact angles for different meshes is presented as a function of laser scanning speed. Stainless steel meshes with 150 µm pore size and copper mesh with 100 µm pore size have demonstrated excellent wettability response for oil and water phases. Vacuum ageing causes rapid chemisorption of hydrocarbons on laser structured surface in the absence of water molecules, rapidly transforming the wetting state from superhydrophilic underwater-superoleophobic to superhydrophobic-superoleophilic state.

Application of high pulse repetition rate lasers opens the way for increasing the average flux of the high-order harmonics generating in the ions- and nanoparticles-containing plasmas ablated on the surfaces of various metal targets. We demonstrate the harmonic generation of 37 fs, 150 kHz, 1030 nm, 0.5 mJ pulses in different plasmas. The formation of plasma plumes on the surfaces of carbon, titanium, boron, zinc, and manganese targets was performed during laser ablation, using 250 fs pulses from the same laser. The ablation of the mixed powder of boron nanoparticles and silver microparticles was used for generation of harmonics with high yield. Harmonics up to the fortieth orders from the carbon plasma were obtained. The estimated conversion efficiencies in laser-produced plasmas were &le, 10&minus, 5. The photon flux for a single harmonic generating in carbon plasma was estimated to be 8 &times, 1013 photons/s.

Luminescence spectra are extremely sensitive to variations in structural environment; thus, result of structural change, such as phase transition, can be observed via luminescence intensity. The temperature dynamic of photoluminescence in the Nb-doped SrTiO3 demonstrates two critical points at 115 and 160 K, which correspond to temperatures of structural phase transitions for the bulk and the surface of SrTiO3, respectively. The absence of a hysteresis effect in the photoluminescence emission points out the correspondence of the critical points to a second-order phase transition. Similar critical behaviours were also observed in oxygen-deficient SrTiO3, confirming a relationship between the PL and phase transition. The existence of peaks in the temperature coefficient of resistivity at the same temperatures also confirms the correlation between photoluminescence and phase transition in the Nb-doped SrTiO3, providing a simple non-contact method to detect phase transitions in luminescence materials.

High-pulse repetition rate lasers allow significant enhancement in the average power of the low-order harmonics generation in isotropic media. We report on the third (343-nm) and fifth (206-nm) harmonics generating in air and different nanoparticle-containing laser-produced plasmas by applying Yb-doped fiber laser delivering 37-fs, 100-kHz, 1030-nm, 0.5-mJ pulses. Different characteristics of these processes (power and density dependences, influence of impeding processes, role of synthesized nanoparticles, variations of the spectral modulation of driving pulses, etc.) are analyzed. We compare the formation of the plasmas on the surfaces of aluminum, carbon, manganese, and titanium bulk species, as well as quantum dots of metal sulfides as the media for low-order harmonics generation, using 250-fs (1030-nm) and 5-ns (1064-nm) heating pulses at different delays between the heating and driving pulses. Average power of about 20 mW was estimated for the third harmonic emission from metal plasmas, with 3 × 1016 UV photons (343 nm) emitted per second.

The search for reliable sources of incoherent and coherent extreme ultraviolet (XUV) radiation in different spectral ranges is an important task in laser physics. Here we report on the incoherent emission of XUV radiation in the region of 6 nm from boron plasma. The optimization of target ablation allowed the generation of XUV emission mainly originated from a single B IV transition (λ = 6.03 nm). We also demonstrate the generation of the 806 nm radiation harmonics up to the 55th order (λ = 14.6 nm) and of tunable near infrared radiation (1280–1400 nm) up to the 35th order (λ=38 nm), during the propagation of femtosecond pulses through boron plasma. The incoherent and coherent emissions from this target were compared and analyzed considering the influence of ionic transitions on the B IV emission and harmonic efficiency. We present different schemes of laser-plasma interaction (two-color pump of B plasma, generation of tunable harmonics in XUV range, formation of structured extended plasma, ablation of boron nanoparticles, laser-induced breakdown spectroscopy, overheating of boron targets, quasi-phase matching of plasma harmonics, etc.) during the ablation of boron-containing targets.

We examine the hydrophobic and hydrophilic properties of the plane and curved surfaces of different materials ablated using 5 ns laser pulses in air. The difference in the contact angles between liquid and surface of the modified graphite and AlNiCo alloy rods using different fluencies of the ablating pulses are demonstrated. The wetting contact angle of ablated graphite rod was found to be 147°, i.e., the modified curved surfaces demonstrated the superhydrophobic properties. On the other hand, the superhydrophilic properties, with 7° wetting contact angle, were demonstrated in the case of ablated aluminum alloy. A schematic model was proposed for the application of the graphite rod as a membrane for the oil–water separation.

We analyze the role of surrounding gas and aging in ambient air in the wettability behavior of laser-processed stainless steel meshes. Laser texturing of meshes was carried out in the presence of different gases (N2, O2, CO2, Ar, and SF6) in ambient atmospheric air and under different vacuum conditions. The influence of each gas on the evolution of the wettability properties after aging in ambient air is analyzed. The effects of low-pressure and vacuum aging allowed transforming the initial superhydrophilic characteristics of the laser-structured meshes to an almost superhydrophobic state.

We report on detailed calculations of high-order harmonic generation (HHG) spectra from Li, Li+, and He using the Lewenstein model. Our model well describes the HHG experiment in Li plasma [J. Phys. B45, 065601 (2012)JPAPEH0953-407510.1088/0953-4075/45/6/065601]. The cutoff position, in the case of neutral lithium atoms (43th harmonic of 800 nm radiation), corresponds to 3.5×1014 W/cm2 laser intensity, as numerically-simulated in the current work. The difference from the experimental value can be well explained by the measurement errors and uncertainty in determining the laser intensity, which is usually around 25%. We found that Li+ ions do not contribute to HHG plateau region of the spectra and that those ions start to contribute only at very high intensities. Our calculations show that the application of materials possessing higher ionization potential does not necessarily leads to the extension of HHG cutoff.

We report on the measurements of the remnant magnetization, and hence critical current, in a single crystal of YBa2Cu4O8. A peak in the temperature dependence of the critical current is observed when the external magnetic field is tilted away from the a&ndash, b planes. The observed behavior is attributed to a thermally activated instability-driven vortex-lattice splitting or vortex chain formation. The nature of the peak and the possibility of a thermally-activated dimensional crossover have been discussed.

Novel methods of coherent short-wavelength sources generation require thorough analysis for their further amendments and practical implementations. In this work, we report on the quasi-phase matching (QPM) of high-order harmonics generation during the propagation of single- and two-color femtosecond pulses through multi-jet plasmas, which allows the enhancement of groups of harmonics in different ranges of extreme ultraviolet. The role of the number of coherent zones, sizes of plasma jets and the distance between them, plasma formation conditions, and the characteristics of the fundamental radiation on the harmonic efficiency at quasi-phase matching (QPM) conditions are analyzed. We demonstrate the ~40&times, enhancement factor of the maximally-enhanced harmonic with respect to the one generated at ordinary conditions in the imperforated plasma.

Using asymmetric two-color laser fields composed of 1800 and 900nm, we have simultaneously controlled four well identified fragmentation channels in dissociative ionization of the hydrogen molecule, resulting in enhanced electron-localization sensitivities of up to 65%.

Wetting properties of metal surfaces play important role in different practical and fundamental applications. In this work we investigate the variation of wetting properties of three different metals (aluminum, copper and galvanized steel) when ablated with ultrafast fiber lasers of femtosecond and picosecond pulse durations. The role of pulse duration and scanning speed used in the laser-surface structuring is analyzed. Scanning electron microscopy, atomic force microscopy, and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) are employed to characterize the roughness and chemistry of the laser-structured surfaces. The degree of hydrophobicity and self-cleaning characteristics of three laser-structured metals are compared when aged in different post-ablation environments. Freshly laser-treated samples of aluminum, copper, and galvanized steel demonstrated superhydrophilic wetting response when their contact angles are measured immediately after laser ablation. The superhydrophilic characteristics of these freshly laser-structured surfaces are found to evolve to hydrophobic state after 30 days of ageing in ambient atmospheric conditions, while they take only 6 h to transform to superhydrophobic state when aged in low-pressure environment. Ultrafast laser-surface nanostructuring, coupled with vacuum ageing, proves to be an effective and rapid approach in achieving extreme superhydrophobic states in different metals, which makes it suitable for a wide range of self-cleaning applications.

The formation of well-controlled nano/micrometer-sized structures on metallic surfaces enables the modification of their optical and wetting properties. Forming such structures on the surface of biocompatible materials, in particular, can expand their applications in various areas of science and technology. Here we present results on covering tantalum (Ta), a biocompatible material, with complex nanosized structures comprising azimuthally- and radially-directed laser-induced periodic surface structures (LIPSS) by rotating the metallic sample with respect to the polarization direction of the irradiating laser pulses. For the first time, we use a high-repetition rate (150 kHz) fiber-based laser with 37 fs ablating pulses and a central wavelength of 1030 nm to form ripples that are directed both parallel and perpendicular to the laser polarization direction on the surface of Ta. Rotating the target during ablation led to forming two distinct zones of structures. The first zone, around the circumference of the target, consisted of both high- and low-spatial-frequency LIPSS, while in the second zone, at the center of the target, was covered by nanoparticles redeposition. We demonstrate how the formation of such complex structures significantly alters the optical reflectance and wetting characteristics of Ta.

The migration of hydrogen atoms resulting in the isomerization of hydrocarbons is an important process which can occur on ultrafast timescales. Here, we visualize the light-induced hydrogen migration of acetylene to vinylidene in an ionic state using two synchronized 4 fs intense laser pulses. The first pulse induces hydrogen migration, and the second is used for monitoring transient structural changes via Coulomb explosion imaging. Varying the time delay between the pulses reveals the migration dynamics with a time constant of 54 ± 4 fs as observed in the H+ + H+ + CC+ channel. Due to the high temporal resolution, vibrational wave-packet motions along the CC- and CH-bonds are observed. Even though a maximum in isomerization yield for kinetic energy releases above 16 eV is measured, we find no indication for a backwards isomerization — in contrast to previous measurements. Here, we propose an alternative explanation for the maximum in isomerization yield, namely the surpassing of the transition state to the vinylidene configuration within the excited dication state.

The positive temperature dynamics in the near-band-edge (NBE) photoluminescence (PL) of Nb-doped SrTiO3 single crystal have been investigated in the temperature range of 10 K–120 K. Intensity of the NBE PL emission with a peak at 3.21 eV has shown increase with increasing temperature. This NBE PL consists of two emission lines with peaks at 3.208 and 3.167 eV. The thermal dynamic in the intensity of the 3.21 eV emission was mainly defined by the temperature behavior of the 3.208 eV transition. The increase in the intensity of the 3.208 eV line with increasing temperature was associated with an increase in the number of electrons thermally excited from the surface. Additionally, a critical point in intensity of the PL at 3.21 eV can be caused by the phase transition, which occurs in Nb-doped SrTiO3 at 115 K.

Aluminum nanoparticles (NPs) demonstrate a variety of applications. Here we study the laser-assisted generation of Al based NPs in liquids and in vacuum, and their ability to change the wettability and nonlinear optical properties of the surfaces, suspensions and plasmas. By means of Molecular Dynamics method we analyzed the formation process of aluminum NPs during the ablation of bulk targets. The numerical simulations allowed identifying the main mechanisms of NPs formation in liquid media and the existence of the optimal laser irradiation parameters for producing Al NPs of the desired size and morphology. We experimentally analyze the variations of the wettability of glass surfaces under the deposition of the NPs produced during laser ablation of aluminum in water and in vacuum. In the former case we demonstrate a significant decrease of contact angle leading to superhydrophilic properties of deposited NPs from water suspension. Meanwhile, the NP-contained films deposited on the glass substrates during ablation of Al in vacuum demonstrated the superhydrophobic features. The low-order nonlinear optical properties of Al NPs produced during ablation of the bulk metal by nano-, pico-, and femtosecond pulses are determined. The coefficients of nonlinear refraction and absorption of Al NPs using 40 fs pulses at λ = 400 nm were measured to be ~ 10-9 cm2 W−1 and 10-7 cm W−1, respectively. Al NPs allowed generation of 37th harmonic using 40 fs pulses propagating nearby to the ablating aluminum target.

We present a systematic study on the control of Cooper minimum (CM) in the high-order harmonics spectra generated during the interaction of Ar gas with ultrashort near-infrared laser pulses. Tailoring the width and depth of CM in argon is demonstrated by changing the gas jet position with respect to the focal plane of focusing lens and by defocusing-assisted phase-matching. We further analyze the influence of single- and two-color laser pump schemes on the appearance of CM. The application of two orthogonally-polarized fields of fundamental radiation and its second harmonic, which is also used to generate controllable yields of odd and even harmonics, led to diminishing the CM in the harmonic spectra. Our experimental findings are supported by theoretical calculations that solve the time-dependent Schrödinger equation in the microscopic domain, and take into account the phase matching in the macroscopic domain.

We propose a modified version for the strong field theory of high-order harmonic generation (HHG) in molecules and we apply it to analyze the orientation-dependences of HHG from the hydrogen molecule and it molecular ion H2+ when exposed to linearly polarized laser light. Our model predicts the presence of clear interference minima in the spectra of the high-order harmonics. We further exploit the orientation-dependence of the interference minima's position and the harmonics polarization properties through proposed model. We found that the position of the interference minima are associated with the polarization properties of harmonics.

We analyze the high-order harmonics generation using 1 kHz and 100 kHz lasers by ablating different rotating targets. We demonstrate the high average flux of short-wavelength radiation using the latter laser, while comparing the plasma formation conditions at different pulse repetition rates. The analysis of harmonic stability in the case of the 100 kHz experiments showed the two-fold decay of the 27th harmonic generating in silver plasma after 3.5×106 shots. The advantages of shorter pulse–induced ablation for the improvement of harmonic generation stability are demonstrated. Two-color pump of plasma, resonance enhancement of single harmonic, and quasi-phase matching studies are presented for 1 kHz laser applications. The formation of modulated multi-jet plasma on the plane and curved surfaces during ablation by 100 kHz pulses is demonstrated. In the case of the 25th harmonic of 1030 nm radiation (E=30 eV) generated during experiments in carbon plasma, at 100 kHz and 40 W average power of driving pulses, 0.4 mW of average power for single harmonic in the 40 nm spectral range was achieved.

High-order harmonic generation (HHG) in atoms and molecules allows the study of the static and dynamic properties of these systems. We present the results of HHG studies in the plasmas produced using femtosecond and picosecond laser pulses on the surfaces of lanthanides and their oxides (La, Yb, Pr6O11, and Tb4O7). The plasmas induced by femtosecond pulses have proven to be a more efficient medium for HHG than the plasmas produced by picosecond pulses in the case of two-color pump HHG. We analyze the advantages of laser ablation using femtosecond pulses for the extension of the cutoff energy of generated harmonic in lanthanide plasma. We have shown that Yb plasma is the efficient medium for the harmonic generation up to the 73rd order, which is one of the largest orders generated in laser-produced plasmas.High-order harmonic generation (HHG) in atoms and molecules allows the study of the static and dynamic properties of these systems. We present the results of HHG studies in the plasmas produced using femtosecond and picosecond laser pulses on the surfaces of lanthanides and their oxides (La, Yb, Pr6O11, and Tb4O7). The plasmas induced by femtosecond pulses have proven to be a more efficient medium for HHG than the plasmas produced by picosecond pulses in the case of two-color pump HHG. We analyze the advantages of laser ablation using femtosecond pulses for the extension of the cutoff energy of generated harmonic in lanthanide plasma. We have shown that Yb plasma is the efficient medium for the harmonic generation up to the 73rd order, which is one of the largest orders generated in laser-produced plasmas.

Attosecond science relies on the use of intense, waveform-controlled, few-cycle laser pulses to control extreme nonlinear optical processes taking place within a fraction of an optical period. A number of techniques are available for retrieving the amplitude envelope and chirp of such few-cycle laser pulses. However, their full characterization requires detection of the absolute offset between the rapidly oscillating carrier wave and the pulse envelope, the carrier–envelope phase (CEP). So far, this has only been feasible with photoelectron spectroscopy, relying on complex vacuum set-ups. Here, we present a technique that enables the detection of the CEP of few-cycle laser pulses under ambient conditions. This is based on the CEP-dependence of directly measurable electric currents generated by the electric field of light in a metal–dielectric–metal nanojunction. The device holds promise for routine measurement and monitoring of the CEP in attosecond laboratories.