We present a systematic experimental comparison of single-pass second-harmonic generation (SHG) in bismuth triborate (BiBO) and lithium triborate (LBO) nonlinear crystals, driven by a 1.3 ps, 91 kHz laser at 1030 nm with up to 57 W of average input power. Both crystals yielded 32 W of second harmonic (SH) output at 515 nm, corresponding to a conversion efficiency of 56 %, which to the best of our knowledge represents the highest SH output power reported in the green spectral region using a BiBO crystal. Power dependence, long-term stability, beam quality, pulse duration, spectral properties, thermal effects, and angular acceptance bandwidth are characterized and directly compared for both crystals. These results provide quantitative performance benchmarks to guide the selection of nonlinear crystals for high-average-power, ultrashort-pulse frequency conversion near 1030 nm.

We present a reference-free computational wavefront sensor based on binary amplitude modulation and phase retrieval. The method employs a Digital Micromirror Device as a programmable amplitude modulator and reconstructs the complex optical field from multiple far-field intensity measurements using the Reweighted Amplitude Flow algorithm with Optimal Spectral Initialization. Unlike classical pupil-plane wavefront sensors, the proposed architecture contains no wavelength-specific optical elements, enabling straightforward adaptation across a broad spectral range. The achievable spatial resolution of the reconstructed wavefront scales directly with the modulator resolution. We experimentally demonstrate wavefront reconstruction at 650 nm and at 2116 nm, a wavelength regime where commercial wavefront sensors are scarce. At 650 nm, the reconstructed wavefront is validated against a commercial lateral shearing interferometer, and the sensor is further integrated into a closed-loop adaptive optics system using a deformable mirror. The proposed approach is particularly suited for applications requiring high spatial resolution and large dynamic range in slowly varying or quasi-static laser fields, where computational reconstruction speed is not a primary concern.

The effects of laser shock peening (LSP) on subtractively manufactured (SM) and additively manufactured (AM) Ti-6Al-4V alloys in pH 2 buffer solution were investigated. LSP increased the surface roughness from 0.25 ± 0.05 μm to 0.6 ± 0.1 μm, raised Vickers hardness by 12-16%, and introduced compressive residual stresses of 400-950 MPa. Microstructural analysis indicated that LSP promoted β-phase formation and grain refinement in SM alloys, while reducing the α'-phase fraction in AM alloys. Electrochemical testing revealed that all LSP-treated specimens exhibited active-passive transitions, unlike the stable passive response of unpeened samples. The corrosion rate (icorr) decreased from approximately 5 × 10-6 to 1 × 10-6 A·cm-2 after LSP. During 24 h potentiostatic polarization at 1.3 VSCE, the passive current density stabilized at 10-8-10-7 A·cm-2, with LSP AM specimens exhibiting values approximately twice those of their unpeened counterparts. Mott-Schottky analysis confirmed that the donor density (ND) in the SM alloy changed negligibly after LSP, indicating a stable passive alloy. In contrast, the ND for the AM alloy increased from 1 × 1019 to 3 × 1019 cm-3, suggesting an oxygen-vacancy-rich, less stable passive film. Overall, LSP reduces the corrosion rate primarily through the introduction of compressive residual stress but may impair the long-term passive-film stability of AM Ti-6Al-4V owing to defect generation. In contrast, the SM alloy maintains passive-film stability under identical treatment conditions.

Predicting the steady-state performance of high-power thin-disk lasers requires not only pump-signal energy transfer but also how disk deformation contributes intra-cavity mode formation. In this work, we address the output-power reduction that occurs even when the laser remains in a single-mode regime with M^2 around 1.1. We developed a numerical model in which the pump-induced inversion is initialized from a non-lasing multi-pass absorption model and then coupled to two-dimensional cavity-field propagation using measured disk optical path difference (OPD) maps. Applied to the Yb:YAG thin-disk laser, the model reproduces the residual pump fraction and predicts the signal power, beam diameter, and M^2 with errors of 3.0%, 1.7%, and 0.05, respectively. To interpret the measured OPD, the disk surface is further analyzed by Zernike decomposition, and the defocus term is converted into an equivalent radius of curvature (eROC). The eROC-based simulation provides the defocus-only reference performance that is theoretically reachable in the absence of higher-order aberrations, whereas the measured-OPD simulation reproduces the experimentally observed power reduction at high pump intensity. The comparison quantitatively shows that higher-order aberrations beyond defocus reduce the overlap with the fundamental cavity mode and limit power scaling, even before strong M^2 degradation appears. This result identifies aberration-induced modal loss as a key limitation in high-power single-mode thin-disk lasers.

A holmium-doped yttrium aluminum garnet (Ho:YAG) thin disk was experimentally investigated under Q-switching and cavity-dumping operation schemes, pumped by a 1.9 & micro;m laser diode (LD). The laser generated pulses at 2090 nm with energies more than 6 mJ and pulse duration down to 3.8 ns, corresponding to a peak power of 1.6 MW with near-diffraction-limited beam quality. The compact and robust system was used for laser-induced breakdown spectroscopy (LIBS) experiments, demonstrating its practical usability. These results represent, to the best of our knowledge, the first demonstration of a Ho:YAG thin-disk laser providing MW peak power in the nanosecond regime.

Tilting waveplates in high-energy laser systems alters effective phase retardance and azimuth, causing polarization changes. Mueller-matrix polarimetry quantifies these tilt-induced effects in large-aperture optics, informing alignment strategies to improve polarization control and overall system performance.

Functional polymer surfaces with tailored wettability, antibacterial and adhesion properties are increasingly required in medical, packaging and consumer applications. Laser structuring of steel mould inserts followed by injection moulding offers a scalable manufacturing route, but conventional single-beam texturing has limited throughput. Here, we present a selective acceleration strategy that applies different laser techniques to micro- and nanostructuring. Deep microhole drilling was accelerated up to 20-fold by operating an ultrashort-pulse fibre laser at a repetition rate of 1 MHz in single-beam mode. For laser-induced periodic surface structures (LIPSS), line-beam shaping with a spatial light modulator increased productivity by 35-fold, reaching processing speeds above 100 cm$^2$ min$^{-1}$ while retaining sub-micrometre fidelity. Replication experiments with polypropylene (PP), PA66 and ABS confirmed successful transfer of micro- and nanostructures, with PP showing the highest fidelity. Vacuum-assisted injection moulding increased replicated feature height by 56--283 percent. All laser-textured PP surfaces showed higher static water contact angles than the untreated reference, reaching approximately $134^\circ$ in the Wenzel regime. Structured PA66 surfaces reduced bacterial retention by up to 99.8 percent for E. coli and approximately 90 percent for S. aureus. Laser texturing also increased the shear strength of PP joints bonded with a non-optimised adhesive by up to 30-fold. This approach provides a practical, coating-free route to functional polymer components and helps bridge the gap between laboratory laser texturing and industrial injection moulding.

We demonstrate real-time wavefront correction in a high-energy high-average-power DiPOLE100/Bivoj laser using adaptive optics. A bimorph deformable mirror and a Shack-Hartmann wavefront sensor reduced wavefront error 10-fold and improved the Strehl ratio 11-fold. Design aspects such as the deformable mirror actuator geometry, optimal placement and loop frequency are discussed for integration into next-generation high-energy high-average-power lasers.

We present results of frequency tripling experiments performed at the Hilase facility on a cryogenically gas cooled multi-slab ytterbium-doped yttrium aluminum garnet laser system, Bivoj/DiPOLE. The laser produces high-energy ns pulses at 10 Hz repetition rate, which are frequency doubled using a type-I phase-matched lithium triborate (LBO) crystal and consequently frequency summed using a type-II phase-matched LBO crystal. We demonstrated a stable frequency conversion to 343 nm at 50 J energy and 10 Hz repetition rate with conversion efficiency of 53%.

This article demonstrates that 3D-printed parts can replace metal parts in optomechanics in the correct circumstances. Three examples are shown: a clamping fork for pedestal holders where stability is important, an adjustable mirror holder where the rigidity is the main criterion, and a stray light shield where the transmissivity is critical. By combining carbon-fiber-reinforced polymers (CFRPs) with 3D printing, it is possible to produce components that fill the gap between standard 3D-printed plastics and metal parts in terms of strength and stability. These parts are designed to be lighter, more compact, and easier to modify, while keeping good mechanical properties such as resistance to vibration, shape accuracy, and controlled thermal expansion. The article focuses on the application of composite 3D printing on optomechanical components. It compares different methods of composite 3D printing, including fused filament fabrication (FFF) with either chopped fibers or with continuous fiber reinforcement. Three examples from the HiLASE Centre demonstrate how these parts are used in practice, confirming that it is indeed possible to 3D print components that are lighter and cheaper yet still highly functional compared to their off-the-shelf counterparts—for example, lightweight and stiff mounts, shielding against stray laser light, or flexible elements allowing fine mechanical adjustments. Simulations of the deformations are included to compare the printed and metal versions. The article ends with a summary of the benefits and limitations of using 3D-printed composites in optomechanics.

Recent advancements in photonics have intensified the performance requirements for optical systems and present significant challenges for optical coating technologies. Conventional interference coating systems often prove to be insufficient, especially in applications requiring large angles of light incidence or a wide wavelength range. Nanostructures, which consist of an air material mixture, offer promising alternatives. In this work, silica nanostructures are manufactured by the AR-plas2 method, in which first an organic layer is evaporated onto a substrate. This organic layer forms self-organizing nanostructures by a plasma etching step, which are subsequently coated with silica. Finally, the organic residues are removed by additional plasma etching and heat treatment steps, which results in hollow silica structures. The work examines the optical and functional properties of these structures designed for 355 nm to demonstrate their use as anti-reflective coatings for advanced optical systems.

We present a study of second harmonic generation (SHG) and third harmonic generation (THG) in lithium triborate (LBO) crystals using a high-energy, 10-J-class, 10 Hz ytterbium-doped yttrium aluminum garnet laser system. We achieved high conversion efficiencies of 75% for SHG and 56% for THG for Gaussian-like temporal pulse shapes and top-hat-like beam profiles. The angular and temperature dependence of the LBO crystals was measured and validated through numerical simulations. The SHG process exhibited an angular acceptance bandwidth of 1.33 mrad and a temperature acceptance bandwidth of 2.61 K, while the THG process showed 1.19 mrad and 1.35 K, respectively. In addition, long-term stability measurements revealed root mean square energy stabilities of 1.3% for SHG and 1.24% for THG. These results showcase the reliability of LBO crystals for high-energy, high-average-power harmonic generation. The developed system offers automated switching between harmonics provided at the system output. The system can be easily adapted to neodymium-doped yttrium aluminum garnet based pump lasers as well.

A high-power picosecond laser offered to users at the HiLASE Laser Centre has been equipped with a harmonics generation system to expand application possibilities. The fundamental beam of 1030 nm is produced by a diode-pumped Yb:YAG thin-disk laser at similar to 1 ps pulse duration and 90 kHz repetition rate. Harmonic frequencies are produced from the fundamental wavelength; second (515 nm), third (343 nm), fourth (258 nm), and fifth (206 nm). The advantage of picosecond pulses when used for materials processing is a small thermal load on the sample surface. UV and DUV processing bring another advantage during the machining: micro-holes production with sharp cutting edges. The visible (VIS, 515 nm) and deep-ultraviolet (DUV, 258 nm) radiation are produced by frequency doubling of the fundamental and visible beams, respectively. The nonlinear crystals used for this are LBO (SHG) and CLBO (FHG). By sumfrequency mixing are generated the ultraviolet (UV) (1 omega + 2 omega = 3 omega, 343 nm) and the deep-ultraviolet (DUV, 1 omega + 4 omega = 5 omega, 206 nm). The crystals used are LBO (Type I, 3 omega) and CLBO (Type I, 5.). We present the latest results achieved at each harmonic, their optical properties and their typical applications. Recently, the laser provided the users with 75 W at the fundamental, up to 39 W at 515 nm, 21 W at 343 nm, 8 W at 258 nm and 1.5 W at 206 nm.

Efficient, high-energy (multi-J), high pulse rate (multi-Hz) nanosecond lasers are required for industrial materials processing, research into high energy density physics phenomena, inertial confinement fusion and pumping of high peak power (few 100s TW to PW) femtosecond amplifiers.

ABSTRACT In the present work, laser shock peening (LSP) was applied on critical areas of ball pins made of 41CrS4 steel to extend their fatigue life. The treatment introduced compressive residual stresses up to a depth of 1 mm with maximum value of −592 MPa on the ball pin surface. This led to a suppression of fretting fatigue in the conical section of the ball pin under lower stress amplitudes and overall fatigue life improvement by a factor of 2.4. After LSP, the crack propagation speed was slowed down to 0.001 μm/cycle down from 0.1 μm/cycle. At high stress amplitudes, the location of the main fatigue crack shifted into a notched part of the ball pin. The combined effect of high stress amplitude and stress concentration changed the elastic strain dominated high cycle fatigue to plastic strain dominated low cycle fatigue where the LSP treatment had no significant impact on the fatigue life.

We report on a compact 2.09-mu m Ho:YAG thin-disk laser directly pumped with a 1.91-mu m diode laser. High-peak-power operation in single-mode beam was achieved using the cavity-dumping technique, producing pulses with 6.2 mJ energy, 3.7 ns duration, 1.7 MW peak power, and 0.66% RMS pulse-to-pulse stability at 500 Hz repetition rate. Performance of the laser system in Q-switched and CW operation will be also presented. High peak power and brightness of the laser output makes it promising for various applications, such as 2-mu m LIDT measurements or as a driving source for laser-induced breakdown spectroscopy.

In this work Laser Peening without Coating (LPwC) was applied underwater on heterogeneous weld joint made of P265GH and X6CrNiTi18-10 steel tubes to prevent Environmental Assisted Cracking on the weld/P265GH steel fusion boundary. Special laser head was designed to precisely deliver 200 mJ green laser beam on the centrally located weld interface on the inner surface of a pipe 76 mm wide and 420 mm long. Residual stress analysis revealed that the LPwC treatment led to generation of compressive residual stresses in the critical fusion boundary area with the magnitude of -168 MPa despite the absence of a protective layer in the peening process. The depth of compressive stresses reached up to 0.8 mm. Plastic deformation induced by LPwC led to grain refinement in the microstructure and improved hardness by 16 %. Samples sectioned from the treated pipe were subjected to accelerated corrosion-mechanical testing which showed more than 2.5x increase in cycles to failure after LPwC. Fractography analysis showed shorter length and decreased number of corrosion cracks after LPwC as well as formation of protective oxide layer on top of the treated surface. 3-point bend testing further showed more than 8x increase in corrosion fatigue life.

Recently, a polarimetric method for thermally-induced polarization change-driven power loss (TIPCL) mitigation in complex laser systems has been developed. However, the final optimization relies on a four-parameter numerical process. This article provides a fully analytical direct calculation alternative to this optimization process. The validity of this approach is demonstrated in previously published data from the pulsed laser system Bivoj/DiPOLE100. The new approach provides a deeper insight into the polarimetric method for TIPCL suppression and also brings a more precise, reliable, and faster alternative to the numerical process used earlier.