Improved stability second harmonic conversion of a diode-pumped Yb:YAG laser at the 0.5 kW level.

We report on efficient and stable, type-I phase-matched second harmonic conversion of a nanosecond high-energy, diode-pumped, Yb:YAG laser. With a frequency-doubling crystal in an enclosed, temperature controller with optical windows, 0.5% energy stability was achieved for approximately half an hour.

Faraday isolator for a 100 J/10 Hz pulsed laser.

We report the first-ever, to the best of our knowledge, demonstration of the optical isolation of a kilowatt average power pulsed laser. A Faraday isolator capable of stable protection of the laser amplifier chain delivering 100 J nanosecond laser pulses at the repetition rate of 10 Hz has been developed and successfully tested. The isolator provided an isolation ratio of 30.

Advanced micro- & nanostructuring for enhanced biocompatibility of stainless steel by multi-beam and beamshaping technology.

Biocompatibility is one of the key issues for implants, especially in the case of stainless steel with medium to low biocompatibility, which may lead to a lack of osseointegration and consequently to implant failure or rejection. To precisely control preferential cell growth sites and, consequently, the biocompatibility of prosthetic devices, two types of surfaces were analyzed, containing periodic nanogrooves laser induced periodic surface structure (LIPSS) and square-shaped micropillars. For the fast and efficient production of these surfaces, the unique combination of high energy ultrashort pulsed laser system with multi-beam and beamshaping technology was applied, resulting in increased productivity by 526% for micropillars and 14 570% for LIPSS compared to single beam methods.

Thermal-stress-induced birefringence management of complex laser systems by means of polarimetry.

The novel method of the thermally-induced polarization changes driven power losses (TIPCL) analysis in the complex laser systems has been developed. The measurement has been tested on the amplifier chain of the 100 J / 10 Hz laser system 'Bivoj' operated at HiLASE Centre. By the usage of the measured non-uniform Mueller matrix of the amplifier chain, the optimization of the ideal input and output polarization state has been calculated numerically.

Adaptive optics system for a short wavelength mid-IR laser based on a Shack-Hartmann wavefront sensor and analysis of thermal noise impacts.

We present an adaptive optics (AO) system for a 1.94-µm laser source. Our system consists of a home-made Shack-Hartmann wavefront sensor and silver-coated bimorph deformable mirror operating in a closed-loop control scheme.

10-µJ few-cycle 12-µm source based on difference-frequency generation driven by a 1-kHz mid-wave infrared OPCPA.

We report on high-energy, few-cycle pulse generation in the long-wave infrared spectral region via difference-frequency generation (DFG) in GaSe and AgGaSe nonlinear crystals. The DFG is driven by the signal at 3.5 µm and idler at 5 µm of a high-power mid-wave infrared optical parametric chirped pulse amplification (OPCPA) system operating at a 1-kHz repetition rate.

Investigation of the lasing performance of a crystalline-coated Yb:YAG thin-disk directly bonded onto a silicon carbide heatsink.

We investigated the use of crystalline coatings as the highly reflective coating of an Yb:YAG thin disk directly bonded onto a silicon carbide heatsink. Compared to commonly used ion-beam-sputtered coatings, it possesses lower optical losses and higher thermal conductivity, resulting in better heat management and laser outputs. We pumped the disk up to 1.

LIPSS-based functional surfaces produced by multi-beam nanostructuring with 2601 beams and real-time thermal processes measurement.

A unique combination of the ultrashort high-energy pulsed laser system with exceptional beam quality and a novel Diffractive Optical Element (DOE) enables simultaneous production of 2601 spots organized in the square-shaped 1 × 1 mm matrix in less than 0.01 ms. By adjusting the laser and processing parameters each spot can contain Laser Induced Periodic Surface Structures (LIPSS, ripples), including high-spatial frequency LIPSS (HFSL) and low-spatial frequency LIPSS (LSFL).

150 J DPSSL operating at 1.5 kW level.

We report on obtaining output energy of 146 J in 10 ns long pulses at 10 Hz repetition rate from Bivoj, a multi-Joule multi-slab cryogenic gas-cooled diode pumped solid state laser, by overcoming its damage threshold bottleneck. This is a 40% energy and power increase of the laser system in comparison to our previous publication and to the most powerful multi-Joule high power laser system.

Towards Rapid Fabrication of Superhydrophobic Surfaces by Multi-Beam Nanostructuring with 40,401 Beams.

Superhydrophobic surfaces attract a lot of attention due to many potential applications including anti-icing, anti-corrosion, self-cleaning or drag-reduction surfaces. Despite a list of attractive applications of superhydrophobic surfaces and demonstrated capability of lasers to produce them, the speed of laser micro and nanostructuring is still low with respect to many industry standards. Up-to-now, most promising multi-beam solutions can improve processing speed a hundred to a thousand times.

Anti-Reflection Nanostructures on Tempered Glass by Dynamic Beam Shaping.

Reflectivity and surface topography of tempered glass were modified without any thermal damage to the surroundings by utilizing 1.7 ps ultrashort pulsed laser on its fundamental wavelength of 1030 nm. To speed up the fabrication, a dynamic beam shaping unit combined with a galvanometer scanning head was applied to divide the initial laser beam into a matrix of beamlets with adjustable beamlets number and separation distance.

Large-Beam Picosecond Interference Patterning of Metallic Substrates.

In this paper, we introduce a method to efficiently use a high-energy pulsed 1.7 ps HiLASE Perla laser system for two beam interference patterning. The newly developed method of large-beam interference patterning permits the production of micro and sub-micron sized features on a treated surface with increased processing throughputs by enlarging the interference area.

Experimental study on compression of 216-W laser pulses below 2 ps at 1030 nm with chirped volume Bragg grating.

We report on the characterization of a high-power, chirped volume Bragg grating (CVBG) pulse compressor. It includes measurements of the CVBG's diffraction efficiency, beam profile, beam quality ( parameter), pulse spectrum, the CVBG's temperature, and the thermal lens. These parameters were monitored for a wide range of input laser powers and with different clamping forces applied on the CVBG.

Laser-induced crystallization of anodic TiO nanotube layers.

In this study, crystallization of amorphous TiO nanotube (TNT) layers upon optimized laser annealing is shown. The resulting anatase TNT layers do not show any signs of deformation or melting. The crystallinity of the laser annealed TNT layers was investigated using X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM).

New observations on DUV radiation at 257 nm and 206 nm produced by a picosecond diode pumped thin-disk laser.

We report new observations on picosecond deep ultraviolet coherent beams generated in a CLBO as the fourth and fifth harmonics of a diode pumped high average power Yb:YAG thin disk laser operating at 77 kHz repetition rate at 1030 nm. The effects of the two-photon absorption were observed, e.g.

High power picosecond parametric mid-IR source tunable between 1.7 and 2.6 μm.

A high-average-power wavelength-tunable picosecond mid-IR source based on parametric downconversion has been developed. The conversion system consists of two stages, optical parametric generator and optical parametric amplifier (OPA), which are pumped by an Yb:YAG thin-disk laser operated at 77 kHz repetition rate, 1030 nm wavelength, and pulse duration down to 1.3 ps.

Picosecond green and deep ultraviolet pulses generated by a high-power 100 kHz thin-disk laser.

We report on the generation of the second (515 nm) and fourth (257.5 nm) harmonics from a 100 kHz diode-pumped solid-state laser operating at a wavelength of 1030 nm which uses one Yb:YAG thin disk in the regenerative amplifier and delivers 60 W of the average output power in pulses of 4 ps duration. Thirty-five W in green light and 6 W in deep ultraviolet (DUV) were achieved.

Cryogenically-cooled Yb:YGAG ceramic mode-locked laser.

This work reports on a liquid-nitrogen-cooled, SESAM mode-locked Yb:YGAG (Yb:Y(3)Ga(2)Al(3)O(12)) ceramic laser. The Yb:YGAG has a similar structure to Yb:YAG, but its emission spectrum at low temperature remains much broader, which is suitable for ultrashort pulse generation and amplification. A stable pulse train with 119-MHz repetition rate was obtained at a wavelength of 1026 nm.

Suppression of nonlinear phonon relaxation in Yb:YAG thin disk via zero phonon line pumping.

A quantitative comparison of conventional absorption line (940 nm) pumping and zero phonon line (ZPL) (969 nm) pumping of a Yb:YAG thin disk laser is reported. Characteristics of an output beam profile, surface temperature, and deformation of a thin disk under the different pump wavelengths are evaluated. We found that a nonlinear phonon relaxation (NPR) of the excited state in Yb:YAG, which induces nonlinear temperature rise and large aspheric deformation, did not appear in the case of a ZPL pumped Yb:YAG thin disk.

Optimization of beam quality and optical-to-optical efficiency of Yb:YAG thin-disk regenerative amplifier by pulsed pumping.

We demonstrate an optimization method of beam quality and optical-to-optical (O-O) efficiency by using pulsed pumping. By changing the pulse duration and the peak intensity of pump pulse at the repetition rate of 1 kHz, the beam quality and O-O efficiency of the Yb:YAG thin-disk regenerative amplifier can be improved. We applied this method to the regenerative amplifier under the pumping wavelength of both 940 and 969 nm, and found that the method was effective in both pumping wavelengths.

Femtosecond pulse parametric amplification at narrowband high power gas laser pumping.

In ultrashort pulse amplification a narrowband gas pump pulse laser has been used for the first time. An all-stage optical parametric chirped pulse amplifier (OPCPA) was driven by a single-shot iodine photodissociation laser. For the first time a broadband amplification was achieved in potassium dihydrogen phosphate crystal at 800 nm seeding.

Comparison of aragonitic molluscan shell proteins.

Acidic macromolecules, as a nucleation factor for mollusc shell formation, are a major focus of research. It remains unclear, however, whether acidic macromolecules are present only in calcified shell organic matrices, and which acidic macromolecules are crucial for the nucleation process by binding to chitin as structural components. To clarify these questions, we applied 2D gel electrophoresis and amino acid analysis to soluble shell organic matrices from nacre shell, non-nacre aragonitic shell and non-calcified squid shells.

Molluscan shell evolution with review of shell calcification hypothesis.

Biomineralization research on mollusc shells has mostly focused on nacre formation. Chitin, silk fibroin protein, and acidic macromolecules are important components for shell formation. Although the principle concept behind shell calcification was developed many years ago, the individual components have not been well scrutinized.

A perspective on errors, bias, and interpretation in the forensic sciences and direction for continuing advancement.

The forensic sciences are under review more so than ever before. Such review is necessary and healthy and should be a continuous process. It identifies areas for improvement in quality practices and services.