BACKGROUND:This study evaluates a novel laser-based pulse-system for weed control characterized by two primary innovations: a thulium-doped yttrium aluminum perovskite (Tm:YAP) laser operating at a 1940 nm wavelength aligned with the peak water absorption band to maximize photothermal efficiency and the implementation of pulsed laser operation. The system's efficacy was examined across varying weed species (dicots and monocots), growth stages (2-3, 4-5, and 7-8 leaf stages), and target locations (growth meristem and stem), alongside technical parameters including beam diameter (0.1-4.7 mm) and exposure time (0.25-2.5 s) and compared against a continuous-wave (CW) system. RESULTS:Targeting the plant stem was significantly more effective than the meristem with mean biomass (proportion of control) values of approximately 0.0 and 0.25, respectively, following a treatment of 1.5 s with beam diameter of 1.6 mm. Across the majority of tested parameters, the pulsed configuration demonstrated no significant advantage over the CW system. Early treatment of the dicot Solanum nigrum at the 2-3 leaf stage resulted with 6% survival using energy density of only 1.5 J mm-2 (0.25 s exposure). However, sensitivity varied greatly by species; Abutilon theophrasti was significantly more susceptible than grass species (e.g., Sorghum halepense), and had a higher effective dose for a 50% response (ED50). CONCLUSION:While pulsed and CW modes yielded similar results, indicating that total energy delivery governs the thermal response, the 1940 nm wavelength demonstrated superior energy efficiency compared to previously reported systems. These findings provide a solid foundation for developing energy-efficient, site-specific robotic weeding technologies. © 2026 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Diamond single crystals are highly promising nonlinear media arising from their extremely high damage threshold, broad transparency window, and potential for phase matching over a wide spectral range. However, in pristine diamond the buildup of even-order nonlinear polarization is forbidden by its centrosymmetric crystal structure. Here, we demonstrate two even-order nonlinear processes from a high-density nitrogen-vacancy (NV)doped diamond sample: broadband terahertz (THz) emission and harmonic generation (HG). In this system, NV centers break the local inversion symmetry, inducing dipoles in the lattice and enabling the buildup of otherwise forbidden even-order responses. The nonlinear THz temporal and spectral emission properties were characterized using time-domain spectroscopy under near-infrared (NIR) femtosecond (fs) excitation, revealing singlecycle, broadband emission extending beyond 4 THz. The HG response in the NIR was investigated using 2.35 mu m fs pulses, with harmonics detected from the 2nd to the 5th order. The NV-diamond cell structure was further analyzed using density functional theory (DFT). Explicit DFT calculations confirm the emergence of a finite second-order nonlinear susceptibility in the NV-diamond system, directly linking the observed THz and HG signals to NV-induced symmetry breaking. This combination of high defect density, internal strain, and the wide bandgap of diamond enables NV-doped diamond to support broadband THz and HG at high intensities without crystal damage.

We investigate resonance-enhanced high harmonic generation (rHHG) in Cr+ by comparing a 1D shape-resonant model, time-dependent density functional theory (TDDFT), and independent particle approximation (IPA) simulations. Previous studies linked rHHG to the 3p -> 3d giant resonance, suggesting a modified four-step model where recolliding electrons are first captured in the autoionizing state before recombining into the ground state, potentially leading to an emission delay associated with the resonance lifetime. While both the 1D-model and TDDFT reproduce experimental spectra, TDDFT reveals that rHHG counterintuitively originates from spin-down 3p states, while spin-up 3d electrons negligibly contribute. The IPA fails to reproduce rHHG, highlighting the significance of electron correlations. Furthermore, TDDFT revealed a correlation induced 480 attosecond time delay, accompanied by a strong phase shift across the resonance, potentially explaining earlier RABBIT measurements. Our work sheds light on long-standing open questions in rHHG and should advance novel ultrafast spectroscopies of electron correlations and resonances.

In this work, a pronounced ultrashort pulse contrast enhancement was realized via the utilization of the nonlinear Transient Grating technique with a fiber-chirped pulse amplifier system in the 1 mu m regime. A YVO4 4 crystal with significantly enhanced nonlinearity relative to glasses yielded a distinct advantage in pulse cleaning by inducing Transient Grating with intensities that are nearly order of magnitude lower compared to, e.g., fused silica. In addition, the clean beam was inherently separated from the generating beams, eliminating the necessity for supplementary filtration, potentially compromising the final contrast. Up to 40 dB contrast enhancement was observed with similar to 1 mu J of energy. The absolute measured peak-to-noise contrast was 80 dB, albeit full verification might be masked by the noise floor limit. Setup modifications for higher pulse energies and corresponding higher efficiencies are underway, with the aim of evaluating their suitability for large laser systems.

The underline physics of resonance high harmonic generation in plasma plumes is still not well understood. A simple model, which is an extension of the well- known three step model predict the capture of the re-colliding electron into an autoionization state and only then return to the ground state while emitting the HHG photon. Another explanation is a better phase matching due to strong variation of the refractive index near resonance. Here we first rule out the second option. Next, we theocratically study the physical mechanism of high-order harmonic generation (HHG) from chromium ions irradiated by intense laser pulses. By performing a combination of state-of-the-art ab-initio and model simulations that agree with well-known experimental observations, we uncover the fundamental physical picture for HHG in Cr+. We found that the main contribution to resonance enhancement originates from initially occupied spin-down 3p states, while spin-up 3d electrons negligibly contribute to resonance HHG. We studied the phase and emission time of each harmonic and compare it to experimental results.

Laser induced x-ray fluorescence were observed against laser polarization ellipticity. While emission from krypton peaks at linear polarization, a signature of recollision, emission from neon shows opposite trend. We attribute it to two competing processes.

The generation and control of large amplitude plasma gratings and other plasma structures is of paramount importance for the realization of plasma photonics. Autoresonant excitation of such structures by means of chirped amplitude-modulated lasers has been recently discussed and analyzed theoretically. Here we discuss the parameter space for the realization of such a scheme and describe the laser system that was built towards this goal. We also expand our earlier theoretical study to account for the more realistic case of a moderately focused laser beam, instead of the simplified plane wave approximation.

We introduce a hybrid CPA system of Yb-doped fibers and Nd:glass rods, with use of aperiodic-frequency-converter crystal around 526 nm, demonstrated ~40% efficiency, and ~40 dB pulse contrast improvement. New result with novel SLT-made-AFC yielded ~60% efficiency, both showed near full bandwidth conversion. A Neodymium:glass CPA pulse yielded record energy result of 320s μJ in 527 nm second harmonic with the LiNBO3. Additionally, new, very low-cost, robust method, based on time-space nonlinear-index self-focusing effect showed >20-dB contrast enhancement.

Probing the wavefunction of an electron under the ‘forbidden zone’ during tunnel ionization is of paramount importance to answer open questions related to it. We used a curved waveguide to simulate tunnel ionization.

The problem of tunneling ionization and the associated questions of how long it takes for an electron to tunnel through the barrier, and what the tunneling rate has fascinated scientists for almost a century. In strong field physics, tunnel ionization plays an important role, and accurate knowledge of the time-dependent tunnel rate is of paramount importance. The Keldysh theory and other more advanced related theories are often used, but their accuracy is still controversial. In previous work, we suggested using a curved waveguide as a quantum simulator to simulate the tunnel ionization process. Here we implemented for the first time such a curved waveguide and observed the simulated tunneling ionization process. We compare our results with the theory.

Here we report on a simple-to-implement and cost-effective approach for laser pulse contrast enhancement, based on the ${\chi}<^>{(3)}$ nonlinear self-focusing effect. An intentionally induced and gently controlled self-focusing in a thin glass transforms the time-dependent intensity into variation in beam divergence. Followed by a spatial discriminating filter, only the strongly focused fraction traverses the setup, at the expense of efficiency. A numerical model, accounting for the pulse and material parameters via a Gaussian ABCD matrix, provides an estimate for the instantaneous beam waist and transmission efficiency, which enables us to evaluate the resulting contrast enhancement. The estimated contrast enhancement spans between 0.5 and 2.5 orders of magnitude, in conjunction with approximately 25%-90% estimated efficiency, depending on the pulse parameters. In a preliminary experiment we demonstrated the effect with 10s-mu J sub GW regime with approximately 40 $\%$ efficiency and a contrast improvement of more than or equal to 20 dB.

Cr:ZnSe laser amplifier resulted more than 40 uJ , 72fs pulses, at λ0 ~ 2375nm. The CEP stability of the parametrically generated seed stands firm through 6 orders of magnitude of amplification.

We demonstrate temporal shape improvement of a short laser pulse using chirped aperiodic nonlinear frequency converter within an optical parametric amplifier. The aperiodic converter generated walk-off free high spatial quality pulse with ∼40% efficiency second harmonic while preserving the pump bandwidth. A <300 fs idler pulse was generated, with ∼10 nm central wavelength tunability around 1053 nm by pump generation and phase matching control. A pronounced contrast pedestal suppression of up to 40 dB was observed within a few picoseconds range around the peak. Such pedestal suppression has good scalability potential to high energies.

Microstructured targets demonstrate an enhanced coupling of high-intensity laser pulse to a target and play an important role in laser-induced ion acceleration. Here we demonstrate an approach that enables us to control the morphology of amorphous solid water (ASW) microstructured targets, by deposition of water vapor on a charged substrate, cooled down to 100 K. The morphology of the deposited ASW structures is controlled by varying the surface charge on the substrate and the pressure of water vapor. The obtained target is structured as multiple, dense spikes, confined by the charged area on the substrate, with increased aspect ratio of up to 5:1 and having a diameter comparable with the typical spot size of the laser focused onto the target.

As one of the most important physical processes of strong-field laser-matter interaction, laser-driven electron-ion recollision is the fundamental process. As we have known, the well-known three-step model of HHG predicts that the cutoff law obeys E-cutoff = I-p + 3.17U(p), implying that the maximum kinetic energy of returning electron can be greatly extended by increasing the driving wavelength. With the long wavelength mid-infrared laser pulse, it is easy for the ponderomotive energy of the returning electron to be very large to excite the deep inner-shell electron, which may be used to investigate the ultrafast inner-shell electron dynamics.

Replacing conventional optical elements with plasma-based optical elements will allow for the manipulation of unprecedented laser intensities. This may enable dynamic manipulation of laser focusing and polarization, at ultrafast time scales, and intensities that are far beyond the optics damage threshold of crystal-based photonics devices. The challenge is to create novel, robust, optical elements on nanosecond timescales. In one approach 1, we create large amplitude nonlinear ion acoustic waves which can act as Bragg structures. The general method of autoresonance is employed to excite and control the structures. Simple analytic and numerical models predict1 relative plasma density modulations greater than unity. The second scheme is to control2 the polarization of a light wave via its interaction with an auxiliary beam in a plasma.

We present an all-passive efficient KGW Raman laser with an external-cavity configuration in the 2 µm spectral regime. The Raman laser was pumped by a passively Q-switched Tm:YAP laser emitting at 1935 nm. Due to the bi-axial properties of the KGW crystal, the laser exhibits stimulated Raman emission at two separate spectral lines: 2272 nm and 2343 nm. The output energies achieved at these two lines are 340 µJ/pulse and 450 µJ/pulse, accordingly. The seed to Raman laser conversion efficiencies achieved of 19.2% and 23.5%, respectively, are comparable to actively Q-switched laser arrangements. To the best of our knowledge, this is the first time an efficient Raman laser in the 2 µm regime is demonstrated in a completely passive configuration.

The dynamics and the decay processes of inner-shell excited atoms are of great interest in physics, chemistry, biology, and technology. The highly excited state decays very quickly through different channels, both radiative and non-radiative. It is therefore a long-standing goal to study such dynamics directly in the time domain. Using few-cycle infrared laser pulses, we investigated the excitation and ionization of inner-shell electrons through laser-induced electron re-collision with the original parent ions and measured the dependence of the emitted x-ray spectra on the intensity and ellipticity of the driving laser. These directly re-colliding electrons can be used as the initiating pump step in pump/probe experiments for studying core-hole dynamics at their natural temporal scale. In our experiment we found that the dependence of the x-ray emission spectrum on the laser intensity and polarization state varies distinctly for the two kinds of atomic systems. Relying on our data and numerical simulations, we explain this behavior by the presence of different excitation mechanisms that are contributing in different ratios to the respective overall x-ray emission yields. Direct re-collision excitation competes with indirect collisions with neighboring atoms by electrons having "drifted away" from the original parent ion.

We demonstrate an external-cavity KGd(WO4)(2) (KGW) Raman laser, pumped by an actively Q-switch Tm:YLF MOPA. The fundamental spectral line emitting at 1881 nm allowed the KGW bi-axial crystal to lase at two separate output spectral lines, 2198 and 2265 nm, depending on the seed polarization axis relative to the KGW's axis. The Tm:YLF seed was amplified using a double-pass Tm:YLF crystal based MOPA setup. After amplification, the seed achieved an output power of 9.15 W, and an energy pulse of 4.57 mJ, a pulse duration of 43 ns at a repetition rate of 2 kHz. The max output average power achieved for the 2265 nm was 1.85 W, with a pulse energy of 0.923 mJ at a repetition rate of 2 kHz implying a conversion efficiency of similar to 20.5%. We noticed a very low conversion efficiency of the shorter KGW spectral shift (at 2198 nm). The reason for this efficiency drop was validated to be the 2nd stokes forming and thus consuming the 1st stokes energy. In favor of the KGW inherent properties and according to the aforementioned results, this crystal appears to be suitable for power scaling as well as for improvement of the Raman conversion efficiency in this spectral range. The KGW crystal is well known for its use in shorter spectral wavelengths. To the best of our knowledge, it is the highest average power achieved by lasing in the 2 mu m region using SRS with KGW.

Cr:ZnSe laser amplifier resulted more than 40 uJ , 72fs pulses, at X0 ~ 2375nm. The CEP stability of the parametrically generated seed stands firm through 6 orders of magnitude of amplification.