Spectra-Physics (Austria)

ABSTRACT: Yerba mate seedling production is inefficient and costly, as the seeds have slow and low germination (<20%) and are often embryoless. Because the plant is grown in low-fertility soils, particularly in terms of phosphorus, nutritional deficiencies in the mother trees likely contribute to poor seed quality. Therefore, this study investigates the impact of phosphorus fertilization on the seed quality of yerba mate (Ilex paraguariensis A. St.-Hil.). The experiment was conducted in a seed production area with 1,822 plants, using P2O5 doses of 0, 48, 96, 182, and 288 kg.ha-1. Seed quality was assessed by the 1% tetrazolium test, thousand-seed weight (TSW), and the seed phosphorus content was determined. The results indicated no difference between treatments in seed phosphorus content or 1,000-seed weight, which was 8.0 g. However, seed viability increased with phosphorus application, with the highest quality observed in the 288 kg P2O5 ha-1 treatment. Phosphorus-fertilized mother plants were 2.58 times more likely to produce seeds with embryos. The study demonstrated that phosphorus plays a fundamental role in seed quality, improving viability and embryo presence.

The Al2024 matrix composites reinforced by different weight percentages of nano-ZrO2 particles prepared by stir-cast method. Physical and mechanical properties (microhardness, compressive test and elastic moduli) of the prepared composites samples were measured. Moreover, the effect of sliding distance and applied load on the wear behavior of all prepared samples was studied. The results showed that the relative density of the Al2024 matrix decreased with increase of the nano-ZrO2 particles while the apparent porosity increased. Moreover, significant improvement in mechanical properties, for example microhardness, ultimate strength, strengthening efficiency and Young’s modulus. The wear rate decreased as the reinforcement content increased while it increased with the increase of the sliding distance and applied load. The microhardness, ultimate strength, bulk modulus of the composites containing 10 wt.% ZrO2 sample improved to approximately 31, 60 and 49%, respectively. For the same sample, the wear rate improved around 20.2 and 21.3 under applied loads 10 and 40 N, respectively.

Ultrashort pulse laser structuring enables direct modification of glass surfaces to generate superhydrophilic properties for anti-fogging applications. This approach makes coatings dispensable and the generated surfaces remain thermally, mechanically, and chemically resistant. However, the laser-generated structures usually cause scattering, which decreases transmission and may disturb the vision through the modified glass in the dry state. The aim of this study was to find a laser-processing strategy to achieve superhydrophilic, anti-fogging properties on glass surfaces with maximum transmission and minimal visual perception of the generated structure. For this purpose, we used an ultrashort-pulsed laser to generate periodic patterns of rippled circles or rough holes with varying pitch. The water contact angle and transmission of the structured glasses were measured as a function of the structured area. It was found that a periodic pattern of holes, which covers less than 1% of the surface, is already sufficient to reach the superhydrophilic state (contact angle < 5°) and provides nearly the same transmission as pristine glass. Pictures of objects imaged through dry, structured glasses, which were placed close to the lens or object, showed in both cases only a minimal decrease of contrast. If this minor drawback can be accepted, this direct laser structuring approach could be an interesting alternative to coating-based techniques and leaves even room to apply additional coatings for the fabrication of multi-functional special glasses.

Heat-sensitive materials, such as polymers, are used increasingly in various industrial sectors such as medical device manufacturing and organic electronics. Medical applications include implantable devices like stents, catheters and wires, which need to be structured and cut with minimum heat damage. Also the flat panel display market moves from LCD displays to organic LED (OLED) solutions, which utilize heat-sensitive polymer substrates. In both areas, the substrates often consist of multilayer stacks with different types of materials, such as metals, dielectric layers and polymers with different physical characteristic. The different thermal behavior and laser absorption properties of the materials used makes these stacks difficult to machine using conventional laser sources. Femtosecond lasers are an enabling technology for micromachining of these materials since it is possible to machine ultrafine structures with minimum thermal impact and very precise control over material removed. An industrial femtosecond Spirit HE laser system from Spectra-Physics with pulse duration 120 μJ and average output powers of >16 W is an ideal tool for industrial micromachining of a wide range of materials with highest quality and efficiency. The laser offers process flexibility with programmable pulse energy, repetition rate, and pulse width. In this paper, we provide an overview of machining heat-sensitive materials using Spirit HE laser. In particular, we show how the laser parameters (e.g. laser wavelength, pulse duration, applied energy and repetition rate) and the processing strategy (gas assisted single pass cut vs. multi-scan process) influence the efficiency and quality of laser processing.

Cutting and drilling of transparent materials using short pulsed laser systems are important industrial production processes. Applications ranging from sapphire cutting, hardened glass processing, and flat panel display cutting, to diamond processing are possible. The ablation process using a Gaussian laser beam incident on the topside of a sample with several parallel overlapping lines leads to a V-shaped structured groove. This limits the structuring depth for a given kerf width. The unique possibility for transparent materials to start the ablation process from the backside of the sample is a well-known strategy to improve the aspect ratio of the ablated features. This work compares the achievable groove depth depending on the kerf width for front-side and back-side ablation and presents the best relation between the kerf width and number of overscans. Additionally, the influence of the number of pulses in one burst train on the ablation efficiency is investigated. The experiments were carried out using Spirit HE laser from Spectra-Physics, with the features of adjustable pulse duration from 16 W ( at 1040 nm wavelength).

Few cycle pulse damage of ultra-broad band chirped mirror was studied with 5 fs pulses showing dramatic damage morphology, which has been analyzed with cross-sectional scanning electron microscopy, showing delamination behavior of the top few layers.

We have developed and characterized ablative and non-ablative femtosecond laser processes for precision machining of transparent materials. Ablation process is compared with a newly developed non-ablative patent pending femtosecond process, ClearShape™, using the Spectra-Physics® Spirit® industrial femtosecond laser.

Optical parametric amplifiers (OPAs) have been used to extend the wavelength range available from amplified Ti:sapphire lasers [1,2]. These systems typically produce 100 fsec pulses throughout the visible and near infrared. Recently, there has been much interest in generating wavelengths beyond 3 μm, often by means of difference frequency mixing [3]. Direct generation of pulses from an OPA however, offers the potential for higher energy. We report, for the first time, generation of 3 to 5 μm pulses directly from a potassium niobate (KNbO3) OPA pumped by an amplified Ti:sapphire laser [4].

The authors have produced transform-limited pulses ranging from 100 ps to 40 fs duration from a Ti:sapphire laser. Output powers in excess of 1 W and peak powers of 0.5 MW have been observed. They describe the technique of regenerative mode locking and present evidence that a transient with a peak power of more than 10 kW is required to initiate mode locking. The role of group velocity dispersion is highlighted and a value of -750 fs/sup 2/ is measured for the group delay dispersion in an operating laser. The authors describe the limits on both the power and pulsewidth obtainable from this laser and present pulse compression experiments which produce 17 fs pulses with 70 mW of average power.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>