Showing papers by "IPG Photonics published in 2020"

Preclinical comparison of superpulse thulium fiber laser and a holmium:YAG laser for lithotripsy

Abstract: A superpulse (500 W peak power) thulium fiber laser operating at a 1940 nm wavelength, suitable for lithotripsy, has recently been developed. The goal of this study was to compare stone fragmentation and dusting performance of the prototype superpulse thulium fiber laser with leading commercially available, high-power holmium:YAG lithotripters (wavelength 2100 nm) in a controlled in vitro environment. Two experimental setups were designed for investigating stone ablation rates and retropulsion effects, respectively. In addition, the ablation setup enabled water temperature measurements during stone fragmentation in the laser–stone interaction zone. Human uric acid (UA) and calcium oxalate monohydrate (COM) stones were used for ablation experiments, whereas standard BegoStone phantoms were utilized in retropulsion experiments. The laser settings were matched in terms of pulse energy, pulse repetition rate, and average power. At equivalent settings, thulium fiber laser ablation rates were higher than those for holmium:YAG laser in both dusting mode (threefold for COM stones and 2.5-fold for UA stones) and fragmentation mode (twofold for UA stones). For single-pulse retropulsion experiments, the threshold for onset of stone retropulsion was two to four times higher for thulium fiber laser. The holmium:YAG laser generated significantly stronger retropulsion effects at equal pulse energies. The water temperature elevation near the laser-illuminated volume did not differ between the two lasers. Distinctive features of the thulium fiber laser (optimal wavelength and long pulse duration) resulted in faster stone ablation and lower retropulsion in comparison to the holmium:YAG laser.

In situ observation of nanolite growth in volcanic melt: A driving force for explosive eruptions

Abstract: Although gas exsolution is a major driving force behind explosive volcanic eruptions, viscosity is critical in controlling the escape of bubbles and switching between explosive and effusive behavior. Temperature and composition control melt viscosity, but crystallization above a critical volume (>30 volume %) can lock up the magma, triggering an explosion. Here, we present an alternative to this well-established paradigm by showing how an unexpectedly small volume of nano-sized crystals can cause a disproportionate increase in magma viscosity. Our in situ observations on a basaltic melt, rheological measurements in an analog system, and modeling demonstrate how just a few volume % of nanolites results in a marked increase in viscosity above the critical value needed for explosive fragmentation, even for a low-viscosity melt. Images of nanolites from low-viscosity explosive eruptions and an experimentally produced basaltic pumice show syn-eruptive growth, possibly nucleating a high bubble number density.

Structure and in vitro dissolution of Mg and Sr containing borosilicate bioactive glasses for bone tissue engineering

Abstract: Borosilicate bioactive glasses are promising for bone tissue engineering. The objective was to assess the impact of magnesium and/or strontium, when substituted for calcium on the glasses' thermal and dissolution properties. Both Mg and Sr substitution appeared to enhance the hot forming domain, i.e. the ability to hot process (sinter, draw fibres) without adverse crystallization. Structural analysis indicated that substitution of MgO and/or SrO for CaO results in changes in the BO3/BO4 ratio as well as in the ratio between bridging and non-bridging oxygen atoms in the silicate structure. Additionally, a de-shielding effect was noticed when Ca, Mg and Sr are present together in the glass network, possibly owing to PO43− charge-balanced preferentially by Na+. The Mg and/or Sr substitution resulted in a lower ion release in simulated body fluid and delayed formation of hydroxyapatite. However, once this layer formed it consisted of a Mg/Sr-substituted apatite. This work highlights the effect of combined ionic substitutions on bioactive glass structure and properties.

Mechanical Imaging of a Volcano Plumbing System From GNSS Unsupervised Modeling

Abstract: Identification of internal structures in an active volcano is mandatory to quantify the physical processes preceding eruptions. We propose a fully unsupervised Bayesian inversion method that uses t...

Chromatographic purification of antimony for accurate isotope analysis by MC-ICP-MS

Abstract: A two-step method for purifying antimony (Sb) from geological samples for accurate measurement of Sb isotopic composition using multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was developed. Sb was separated from the matrix using two successive chromatographic columns loaded with AG 1-X4 and AG 50W-X8 resin, respectively. The separation method was calibrated using geological samples by assessing the extraction yield and the reproducibility of the measured isotopic composition, and resulted in a relatively low procedure blank and better recovery (98.7% ± 5.6%, n = 8, 2SD) compared to previous studies. The validation of the whole protocol, together with instrumental analysis, was confirmed by the investigation of the matrix effect and the result of a standard addition experiment. A combined sample-standard bracketing and external normalization (SSB-EN) method using cadmium (Cd) as an internal element was used for mass bias correction, which gave a reproducibility better than 0.04‰ (2SD). A variation of 0.29‰ of the δ123Sb value (relative to the NIST SRM 3102a standard) was observed in artificial and geological samples, implying the potential application of Sb isotopes in various environments.

High-efficient kW-level single-mode ytterbium fiber lasers in all-fiber format with diffraction-limited beam at wavelengths in 1000-1030 nm spectral range

Abstract: The kW-level single-mode Yb fiber lasers at wavelengths in 1000 -1030nm spectral range with diffraction-limited beam and with direct diode pumping are remarkable high brightness and low quantum defect sources for tandem pumping of multi-kilowatt fiber and crystal laser systems. In this paper we present SM Yb fiber lasers in all-fiber format with powers 0.75kW, 0.90kW, 1.33kW and 1.40kW at 1007nm, 1010nm, 1018nm and 1030nm respectively with M2 values of output beams < 1.1. These are the highest powers of single mode CW Yb fiber lasers at wavelengths near 1 micron to the best of our knowledge. The fiber oscillators with direct diode pumping are highly efficient and have optical slope efficiencies from 64% at 1007nm to 78% at 1018nm relative to total laser diode pump power. The fiber lasers have 3-5m output delivery cable terminated with a LC-8 connector in dependence on power level and MFD of output fiber. The pump and non-linear process (SRS and MI) limitations are discussed.

Wavelength tunable, single-longitudinal-mode optical parametric oscillator with a transversally chirped volume Bragg grating.

Abstract: We report on single-longitudinal-mode (SLM) operation of a low-threshold optical parametric oscillator, with a 17 nm tunability near 2 µm. The oscillator uses a MgO:PPLN crystal in Type 0 quasi-phase-matching configuration, pumped by a 1.064 µm SLM laser. Despite the huge acceptance bandwidth near-degeneracy of MgO:PPLN, spectral selection down to a SLM is achieved by combining a volume Bragg reflector and Vernier filtering in nested signal and idler cavities. Tunability over 17 nm is demonstrated owing to a transverse chirp of the grating period of the Bragg reflector.

Magnetar formation through a convective dynamo in protoneutron stars.

Abstract: The release of spin-down energy by a magnetar is a promising scenario to power several classes of extreme explosive transients. However, it lacks a firm basis because magnetar formation still represents a theoretical challenge. Using the first three-dimensional simulations of a convective dynamo based on a protoneutron star interior model, we demonstrate that the required dipolar magnetic field can be consistently generated for sufficiently fast rotation rates. The dynamo instability saturates in the magnetostrophic regime with the magnetic energy exceeding the kinetic energy by a factor of up to 10. Our results are compatible with the observational constraints on galactic magnetar field strength and provide strong theoretical support for millisecond protomagnetar models of gamma-ray burst and superluminous supernova central engines.

Spectroscopic characterization of Fe:ZnAl2O4, Fe:MgAl2O4 and Fe:InP crystals for mid-IR laser applications

Abstract: There is strong demand for effective gain materials for the 3.0-3.9 μm spectral range not nicely covered by Cr:ZnSe and Fe:ZnSe amplification bands. We characterized, Fe:ZnAl2O4 ceramic sample, Fe:MgAl2O4 and Fe:InP single crystals as promising laser materials for this mid-IR spectral range. In all crystals, the absorption bands corresponding to 5E↔5T2 transition of Fe2+ ions in the tetrahedral sites were measured. In addition, absorption band of Fe2+ ions in the octahedral sites were observed in Fe:ZnAl2O4 sample with maximum absorption cross-section at ~1.0 μm. From the absorption measurements, the radiative lifetime of Fe:MgAl2O4 was calculated to be 60 μs. Saturation absorption of Fe2+ ions in Fe:ZnAl2O4 was studied using Ho:YAG@2.09 μm and Er:YAG@2.94 μm lasers. Saturation measurements were taken up to energy density of 2 J/cm2 and showed no saturation of absorption. This can be explained by a fast non-radiative (<100 ps) relaxation time from the 5T2 level of Fe2+ ions in the Fe:ZnAl2O4 sample at RT. A strong mid-IR photoluminescence (PL) signal in Fe:InP crystal was detected under the direct excitation of the 5E↔5T2 transition of Fe2+ ions using Er:YAG@2.94 μm laser as well as excitation using photo-ionization process under radiation from Nd:YAG@1.064 μm laser. This indicates that Fe:InP crystals could become promising mid-IR laser media with optimization of fabrication technology.

Prospects of Massive Parallelism in Si-Photonic Transceivers for SDM Networks

Abstract: The continues increase in bandwidth demands in optical communication pushes transceivers modules towards higher levels of integration and lower power consumption and cost. Spatial division multiplexing (SDM) is being seen as the solution to bridge the gap between data generation and transport. We review the current status for photonic integration and outline the prospects of SDM and photonic integration combined for future opportunities.

Patterning and removal of circuit board material using ultrafast lasers

Abstract: A method for fabricating a printed circuit, comprising: darkening a surface location of a conductive material with one or more ultrafast pulses of laser radiation and ablating the conductive material at the surface location with one or more longer duration pulses of laser radiation to produce traces or micro via patterns on the surface of a PCB. A hole for a blind micro via is produced by ablating the conductive material at the darkened surface location with one or more longer duration pulses of laser radiation and cleaning a second conductive material under the substrate with one or more further longer duration pulses of laser radiation.

Optical Frequency Comb Based on Cr:ZnS Laser

Abstract: We report mid-IR frequency comb with 3.25 W average power and spectrum spanning 60 THz near 2.4 μm. We stabilized the offset frequency of the comb with accumulated phase error of 75 mrads.

Gas Shielding Device for Use with a Laser Processing Head

Abstract: A gas shielding device may be used with a laser processing head, such as a welding head, to diffuse and distribute a shield gas over a larger gas shielding area for shielding a larger area of metal. The gas shielding device may be coupled to the laser processing head to move with the laser beam and may be arranged coaxially to provide the larger shielding effect in all directions of welding. The gas shielding device is particularly useful for welding titanium or other metals that are highly reactive with gases in the air and/or for larger welding areas (e.g., where the laser beam is wobbled).

Frontiers of Ultrafast Mid-IR Lasers Based on Polycrystalline TM:II-VI Semiconductors

Abstract: We give an overview of recent experimental results on mid-IR femtosecond lasers and optical frequency combs based on TM:II-VI media providing access to few-cycle pulses with Watt-level power over 2–20 µm spectral range.

Pulse configurable fiber laser unit

Abstract: A pulse configurable laser unit is an environmentally stable, mechanically robust, and maintenance-free ultrafast laser source for low-energy industrial, medical and analytical applications. The key features of the laser unit are a reliable, self-starting fiber oscillator and an integrated programmable pulse shaper. The combination of these components allows taking full advantage of the laser's broad bandwidth ultrashort pulse duration and arbitrary waveform generation via spectral phase manipulation. The source can routinely deliver near-TL, sub-60 fs pulses with megawatt-level peak power. The output pulse dispersion can be tuned to pre-compensate phase distortions down the line as well as to optimize the pulse profile for a specific application.

Advanced Solid-State Lasers 2019: focus issue introduction

Abstract: This joint issue of Optics Express and Optical Materials Express features 17 state-of-the art articles written by authors who participated in the international conference Advanced Solid-State Lasers held in Vienna, Austria, from September 29 to October 3, 2019. This introduction provides a summary of these articles that cover numerous areas of solid-state lasers from materials research to sources and from design to experimental demonstration.

Record Unrepeatered 400G 16QAM Signal Transmission over 526 km of Terrestrial Ultra-Low Loss Optical Fiber

Abstract: We demonstrated a record transmission of 400G 16QAM signal over 526 km of terrestrial ultra-low loss and large effective area fibers. Third-order Raman amplifiers and Remote Optical Pump Amplifiers (ROPA) were used to achieve the best-in-class performance. The total span loss was 86.24 dB.

Systems and Methods for Monitoring and/or Controlling Wobble-Processing Using Inline Coherent Imaging (ICI)

Abstract: A system and method may be used to monitor and/or control material processing where a process beam is moved in a wobble pattern, such as a wobble-welding process. While at least one process beam is moved according to a wobble pattern on a processing site (e.g., a weld site) of a workpiece, an ICI system moves an imaging beam at least partially independently of the process beam to one or more measurement locations on the wobble pattern and obtains ICI measurements (e.g., depth measurements) at those locations. The ICI measurement(s) may be used, for example, to evaluate keyhole and/or melt pool characteristics during a welding process. Although the present application describes wobble welding processes, the systems and methods described herein may also be used with other material processing applications where a laser or other energy beam is wobbled or dithered during processing including, without limitation, additive manufacturing, marking and material removal.

Long-wave IR femtosecond supercontinuum generation with Cr:ZnS lasers

Abstract: We give an overview of experimental results on mid-IR femtosecond lasers and frequency combs based on polycrystalline Cr$^{2+}$: ZnS providing access to few-cycle pulses in the spectral range 2–$;3\mu \mathrm{m}$. We also discuss the techniques for generation of multi-octave coherent femtosecond continua with Cr$^{2+}$: ZnS lasers.

Advanced Solid-State Lasers 2019: focus issue introduction.

Abstract: This joint issue of Optics Express and Optical Materials Express features 17 state-of-the art articles written by authors who participated in the international conference Advanced Solid-State Lasers held in Vienna, Austria, from September 29 to October 3, 2019. This introduction provides a summary of these articles that cover numerous areas of solid-state lasers from materials research to sources and from design to experimental demonstration.