Abstract Extreme nonlinear interactions of THz electromagnetic fields with matter are the next frontier in optics. However, reaching this free space is limited by existing lack appropriate powerful sources. Here, we experimentally demonstrate that two-color filamentation femtosecond mid-infrared laser pulses at 3.9 μm allows one to generate ultrashort sub-cycle sub-milijoule energy and conversion efficiency 2.36%, resulting field amplitudes above 100 MV cm −1 . Our numerical simulations...

Generation and application of energetic, broadband terahertz pulses (bandwidth ~0.1-50 THz) is an active contemporary area research. The main thrust toward the development efficient sources with minimum complexities-a true table-top setup. In this work, we demonstrate generation radiation via ultrashort pulse induced filamentation in liquids-a counterintuitive observation due to their large absorption coefficient regime. generated energy more than order magnitude higher that obtained from...

An important challenge in the field of three-dimensional ultrafast laser processing is to achieve permanent modifications bulk silicon and narrow-gap materials. Recent attempts by increasing energy infrared ultrashort pulses have simply failed. Here, we establish that it because focusing with a maximum numerical aperture about 1.5 conventional schemes does not allow overcoming strong nonlinear plasma effects pre-focal region. We circumvent this limitation exploiting solid-immersion focusing,...

Nonlinear THz photonics is probably the last frontier of nonlinear optics. The strength both electric and magnetic fields these ultrashort low frequency light bunches opens way to exciting science applications. Progress in field though slow because deficiency suitable sources. Here we show that two-color filamentation mid-infrared 3.9 um laser pulses allows one generate single cycle with multi-millijoule energies extreme conversion efficiencies. Moreover, focused peak reach values GV/cm kT,...

Although tightly focused intense ultrashort laser pulses are used in many applications from nano-processing to warm dense matter physics, their nonparaxial propagation implies the use of numerical simulations with vectorial wave equations or exact Maxwell solvers that have serious limitations and thus hindered progress this important field up now. Here we present an elegant robust solution allows one map problem on can be addressed by simple scalar equations. The is based a transformation...

Abstract Ultrafast laser welding is a fast, clean, and contactless technique for joining broad range of materials. Nevertheless, this cannot be applied bonding semiconductors metals. By investigating the nonlinear propagation picosecond pulses in silicon, it elucidated how evolution filaments during prevents energy deposition at semiconductor–metal interface. While restrictions imposed by effects usually inhibit countless applications, possibility to perform ultrafast demonstrated. This...

Abstract The ability to create surface structures with precisely controlled chirality remains a major challenge in laser‐matter interaction experiments. In this work, the of vortex laser beams, characterized by spiral polarization patterns and twisted wavefronts, rough metallic surfaces order is theoretically studied. Using numerical simulations based on finite‐difference time‐domain method, how spin orbital angular momenta influence inhomogeneous energy absorption at investigated optical...

We theoretically study the generation of terahertz (THz) radiation by two-color filamentation ultrashort laser pulses with different wavelengths. consider wavelengths in range from 0.6 to 10.6 μm, thus covering whole existing and future powerful sources near, mid far-infrared. show how parameters filaments generated THz depend on wavelength. demonstrate that there is an optimal wavelength for provides highest conversion efficiency results extremely intense single cycle fields.

We demonstrate both theoretically and experimentally that the harmonics from abruptly auto-focusing ring-Airy beams present a surprising property, they preserve phase distribution of fundamental beam. Consequently, this "phase memory" inherits to abrupt autofocusing behavior, while, under certain conditions, their foci coincide in space with one fundamental. Experiments agree well our theoretical estimates detailed numerical calculations. Our findings open way for use such strong field science.

We show the existence of a family waves that share common interesting property affecting way these propagate and focus. The are superposition twin waves, which conjugate to each other under inversion propagation direction. In analogy holography, "real" "virtual" related, respectively, converging diverging parts beam can be clearly visualized in real space at two distinct foci action focusing lens. Analytic formulas for intensity distribution after derived, while numerical experimental...

Recent advances in ultrafast laser 3D writing offer direct fabrication of in-chip silicon microsystems, but this technique remains extremely challenging, because propagation nonlinearities that limit energy localization inside narrow-band-gap materials. This study examines the complex flux and subsequent unusual modification due to intense picosecond pulses from a thulium-doped fiber laser. The best conditions for reliable data inscription deep are identified, which is critical step toward...

We find the spectral bandwidth scaling laws of THz wave packets, produced from two-color laser filaments, as a function input laser-pulse duration and demonstrate how one can fully recover original broadband packets even using narrow-band detection techniques such widespread electro-optic sampling.

Two-color filamenation in gases is known to produce intense and broadband THz radiation. There are two physical mechanisms responsible for the generation this scheme: four-wave mixing emission from induced plasma currents. The case when main second harmonic linearly polarized well studied including impact each of above mechanisms. However, cases two-color fields have complex polarization states role formation still under-explored. Here we use both photocurrent models order consider by with...

We experimentally demonstrate that the terahertz (THz) emission from two-color laser filaments in gases is strongly affected by pulse repetition rate of driving laser. show at rates above 100 Hz, propagation every next train altered gas density depressions produced preceding pulses. As a result, plasma channels higher become shorter, leading to less efficient THz generation. In particular, we observe 50% decrease emitted energy when increases 6 Hz kHz.

In-volume ultrafast laser direct writing of silicon is generally limited by strong nonlinear propagation effects preventing the production modifications. By using advantageous spectral, temporal, and spatial conditions, we demonstrate that modifications can be repeatably produced inside silicon. Our approach relies on irradiation at $\ensuremath{\approx}2$ $\ensuremath{\mu}\mathrm{m}$ wavelength with temporally distorted femtosecond pulses. These pulses are focused in a way spherical...

Propagation in the air of laser radiation with wavelengths range from 248 to 1240 nm are investigated numerically. It was shown that intensity a filament weakly depends on wavelength long-wave region and decreases significantly UV region. Electron concentration plasma channel increases decrease dependence close quadratic. With an increase characteristic scale variation pulse cross section, radii increase.

We developed a model of femtosecond filamentation which includes high-order Kerr effect and an arbitrary polarization laser pulse. show that circularly polarized pulse has maximum filament intensity. Also, we that, independently the initial polarization, value intensity tends to either linearly or

We demonstrate that paraxial ring-Airy beams can approach the wavelength limit, while observing a counterintuitive, strong enhancement of their focal peak intensity. Using numerical simulations, we show this behavior is result coherent constructive action and nonparaxial energy flow. A simple theoretical model enables us to predict parameter range over which possible.

Stationary self-focusing of collimated elliptic Gaussian beams is studied numerically. It shown that the critical power increases with increasing axial ratio initial cross section. Self-focusing accompanied by oscillations beam transverse size caused competition between diffraction-limited divergence and nonlinear compression. As a/b≥3 increases, aberration occurs, at which, after formation several intensity maxima in section, a global maximum appears centre, which forms focus. The...

The influence of focusing conditions (numerical apertures from 0.004 to 0.06) on absolute energetic characteristics third harmonic generation (THG) in air was experimentally studied for pumping 1R (744 nm wavelength) femtosecond laser pulses. THG observed both sub-critical and super-critical pulses the linear non-linear propagation modes, respectively. maximum efficiency 1.6 × 10−3 obtained our experiments at tight pulse powers.

We derive nonparaxial input conditions for simulations of tightly focused electromagnetic fields by means unidirectional vectorial propagation equations. The derivation is based on the geometrical optics transfer incident electric field from significantly curved reflecting surfaces such as parabolic and conical mirrors to plane, with consideration finite thickness focusing element large convergence angles, making nonparaxial. have benchmarked numerical solutions equations initiated against...

The formation of many filaments in a laser pulse with initial perturbations the intensity propagated turbulent atmosphere is studied numerically. It shown that competition between nonlinear focuses can slow down during their propagation. number increases distance. Nonstationary interference upon defocusing plasma leads to appearance secondary filaments. dynamic produced shortens length and channels.