High-power Diode Laser System Research Articles

Clinical experience of transbronchoscopic laser ablation for central airway stenosis using a high-power diode laser-ten years' experience at a single institute.

High-power diode (GaAlAs) laser systems have been used for transbronchoscopic laser ablation for central airway stenosis. Such diode laser systems show a similar clinical effect to a conventional Nd-YAG laser, but the instrument is more compact with easier handling. We use a high-power diode laser system with a non-contact probe for endobronchial ablative therapy. The present study reviewed our experience with transbronchoscopic laser ablation to explore a better clinical approach for managing central airway lesions. We retrospectively reviewed the patients who were treated for central airway lesions by transbronchial laser ablation using the non-contact-type probe from January 2005 to December 2015 at Chiba University Hospital. We investigated the cause of stenosis, number of treatments, laser setting, total amount of energy, complications, and simultaneously performed modality. Thirty-three patients underwent treatment a total of 72 times. There were 23 males, with an average age of 60.3 years old (range, 18-80 years old). The primary causes of the central airway stenosis were neoplastic disease in 22 (16 malignant tumors, 6 benign tumors) and non-neoplastic disease in 11. Among malignant tumors, there were eight tracheal cancer and five lung cancer patients as well as three patients with esophageal cancer. Among benign tumors, there were three hamartomas and one patient each with papilloma, smooth muscle tumor, and glomus tumor. The non-neoplastic causes of airway stenosis were intubation or tracheotomy in four patients, tuberculosis and granulation in two each, and trauma, burn, and surgery in one each. The numbers of treatments were 30 times (1.36 times/patient) for neoplastic diseases and 42 times (3.82 times/patient) for non-neoplastic disease. The total amount of energy was 1,936 J on average (1,674 J for neoplastic diseases and 2,098 J for non-neoplastic disease). There were no major complications related to transbronchial laser ablation therapy. Transbronchoscopic laser ablation using a diode laser system with a non-contact probe can be safely performed and is useful for endobronchial treatment of both neoplastic and non-neoplastic central airway lesions.

Micro-optics assembly for fast axis collimation by means of convolutional neural network.

The manufacture of high-power diode laser systems highly depends on the quality of the collimation of semiconductor laser diodes. The collimation process is conducted by precise alignment of micro-optics, where the first and the most critical step is the placement of the fast axis collimator (FAC) lens. The sub-micron positioning of the FAC lens is conventionally conducted with an active alignment strategy by monitoring changes in the laser beam profile with an external sensitive camera. The optimization of the beam profile characteristics is controlled by a specifically programmed motorized robotic aligner. However, active alignment, a very accurate method, often results in a higher cycle time than the passive approach, where the lens is placed in a pre-measured position. Here, we developed a new active approach, without closed loop control to position the micro-optics, that relies on the use of a pretrained convolutional network (CNN). We trained and evaluated three CNNs that can predict the optimal lens position using the single camera image of the laser beam. We predict that implementation of the best performing CNN-based model would lead to a decrease in alignment time from tens of seconds to hundreds of milliseconds and will be broadly applied in a high-volume manufacturing environment.

Design of high efficiency diode laser module for wireless power transmission

Laser wireless power transmission in unmanned aerial vehicle, satellite station and lunar robot power supply has potential application prospect, whose efficiency becomes the key to the application bottleneck. In order to improve the electro-optic conversion efficiency of the transmitter, the spot uniformity and the effective power ratio in window at the receiver, a design scheme of high efficiency diode laser for the transmitter of laser wireless power transmission was proposed. A high power and high efficiency diode laser system was designed, which is based on space combination with high efficiency, what’s more, the unevenness of the intensity at the receiving end can be optimized to 0.207, and the power ratio in the effective window is more than 94%. A laser wireless power transmission experimental device was built, whose power is over kilowatt, and the rectangular spot was outputted directly by diode laser system, which is matched with rectangular photovoltaic cell, thus the battery array layout rate was improved. The feature of multi-beam modulation was used to improve uniformity of the intensity, which is beneficial to improve the optic–electro conversion efficiency of battery and simplify the power management at the receiving end. The design and research provide reference for the practical application of laser wireless power transmission.

Experimental Study on Effect of Laser Hardening Parameters on Carbon Steel, Non-Malleable Cast iron and X20Cr13 Materials

Laser hardening is a surface heat treatment process used to enhance tribological and mechanical properties of metals which also leads to increase in service life of the components. Material removal, wear and tear, load concentration occurs mostly at rotating and reciprocating parts. Hence it is sufficient to enhance the hardness of a component at functional areas rather than the entire component. Laser hardening process is designed to change the microstructure of metals through controlled heating and cooling to get a modified surface. The constraints of traditional surface heat treatment process such as inability to treat specific area, distortion, poor degree of controllability, requirement of a quenching medium, long cycle time can be overcome by using Laser surface heat treatment and in addition to that it can be automated. With its benefits Laser surface hardening turns out to be a cost effective and energy saving process. The presented work is an investigation of the laser surface hardening via experimental results making use of a 6 axis robotic arm and a 10KW high power diode laser system as heat source with a wavelength of 980nm on leading automotive parts such as retainer, hub, and turbine blade whose materials being non-malleable cast iron, carbon steel, X20Cr13 respectively. Process parameters such as laser power from power source, scan speed were varied to understand the influence on resulting heat treated surface and efforts were made to optimize the process parameters to attain maximum hardness for the component to enhance its working life.

High Power High Efficiency Diode Laser Stack for Processing

High-power diode lasers based on GaAs semiconductor bars are well established as reliable and highly efficient laser sources. As diode laser is simple in structure, small size, longer life expectancy with the advantages of low prices, it is widely used in the industry processing, such as heat treating, welding, hardening, cladding and so on. Respectively, diode laser could make it possible to establish the practical application because of rectangular beam patterns which are suitable to make fine bead with less power. At this power level, it can have many important applications, such as surgery, welding of polymers, soldering, coatings and surface treatment of metals. But there are some applications, which require much higher power and brightness, e.g. hardening, key hole welding, cutting and metal welding. In addition, High power diode lasers in the military field also have important applications. So all developed countries have attached great importance to high-power diode laser system and its applications. This is mainly due their low performance. In this paper we will introduce the structure and the principle of the high power diode stack.

Microstructural characterization of Ni-based self-fluxing alloy after selective surface-engineering using diode laser

The microstructural characterization of thermal-sprayed Ni-based self-fluxing alloy (Metco-16C®) after laser-assisted homogenization treatment was performed. To this end, a high-power diode laser system was used. This supported the real-time control of the target homogenization temperature at the substrate surface. Non-homogeneities of the macrosegregation of certain elements (C and Cu) and the local concentration of Cr-based carbides and borides in certain regions in the as-sprayed state could be enhanced with the application of homogenization. After homogenization at 1423 K, the hardness of the thermal-sprayed layer was found to have increased by 1280 HV from the as-sprayed state (750 HV). At this homogenization temperature, the microstructure of the thermal-sprayed layer consisted of a lamellar structuring of the matrix phase (austenite and Ni3Si) with fine (<5 μm) carbides and borides (the rod-like phase of Cr5B3, the lumpy phase of M23C6, and the extra-fine phase of M7C3). Despite the formation of several kinds of carbides and borides during homogenization at 1473 K, the lowest hardness level was found to be less than that of the as-sprayed state, because of the liquid-state homogenization treatment without formation of lamellar structuring between austenite and Ni3Si.

Laser-assisted selective fusing of thermal sprayed Ni-based self-fluxing alloys by using high-power diode lasers

Fusing treatment of Ni-based self-fluxing alloys (Metco-16C and 1276F) was performed using high-power diode lasers to control the temperature of the substrate’s surface in real time. The effects of the fusing treatment temperature on the microstructural change and hardness distribution were also investigated. For Metco-16C and 1276F, the macrostructural inhomogeneity (voids) within the thermal sprayed layer decreased considerably as the fusing temperature increased. For both self-fluxing alloys, the optimal temperature for fusing was approximately 1423 K (for Metco-16C) and 1373 K (for 1276F), both of which are within the solid state temperature range; these temperatures maximize the alloy hardness together with the macrostructural homogeneity. In this temperature range, the microstructure consists of a lamellar-structured matrix phase with fine (<5 μm) carbides and borides. Selective fusing for a thermal sprayed layer 0.2–0.5 mm in thickness could be successfully achieved in a high-power diode laser system.

Optical design and development of a fiber coupled high-power diode laser system for laser transmission welding of plastics

Eva Rodriguez-VidalIban QuintanaJon EtxarriUrko AzkorbebeitiaDeitze OtaduyIK4-TEKNIKERPolo Tecnologico de EibarCalle Inaki Goenaga, 520600 Eibar, Gipuzkoa, SpainE-mail: erodriguez@tekniker.esFrancisco GonzalezFernando MorenoUniversity of CantabriaGroup of OpticsApplied Physics DepartmentAvenida de los Castros, s/n39005, Santander, SpainAbstract. Laser transmission welding (LTW) of thermoplastics is a directbonding technique already used in different industrial applications sectorssuch as automobiles, microfluidics, electronics, and biomedicine. LTWevolves localized heating at the interface of two pieces of plastic to bejoined. One of the plastic pieces needs to be optically transparent tothe laser radiation whereas the other part has to be absorbent, beingthat the radiation produced by high power diode lasers is a good alterna-tive for this process. As consequence, a tailored laser system has beendesigned and developed to obtain high quality weld seams with weldwidths between 0.7 and 1.4 mm. The developed laser system consistsof two diode laser bars (50 W per bar) coupled into an optical fiberusing a nonimaging solution: equalization of the beam parameter product(BPP) in the slow and fast axes by a pair of step-mirrors. The powerscaling was carried out by means of a multiplexing polarization technique.The analysis of energy balance and beam quality was performed consid-ering ray tracing simulation (ZEMAX®) and experimental validation. Thewelding experiments were conducted on acrylonitrile/butadiene/styrene(ABS), a thermoplastic frequently used in automotive, electronics and air-craft applications, doped with two different concentrations of carbon nano-tubes (0.01% and 0.05% CNTs). Quality of the weld seams on ABS wasanalyzed in terms of the process parameters (welding speed, laser powerand clamping pressure) by visual and optical microscope inspections.Mechanical properties of weld seams were analyzed by mechanicalshear tests. High quality weld seams were produced in ABS, revealingthe potential of the laser developed in this work for a wide range of plasticwelding applications.

Fastin situphase and stress analysis during laser surface treatment: A synchrotron x-ray diffraction approach

An in situ stress analysis by means of synchrotron x-ray diffraction was carried out during laser surface hardening of steel. A single exposure set-up that based on a special arrangement of two fast silicon strip line detectors was established, allowing for fast stress analysis according to the sin(2)ψ x-ray analysis method. For the in situ experiments a process chamber was designed and manufactured, which is described in detail. First measurements were carried out at the HZG undulator imaging beamline (IBL, beamline P05) at the synchrotron storage ring PETRA III, DESY, Hamburg (Germany). The laser processing was carried out using a 6 kW high power diode laser system. Two different laser optics were compared, a Gaussian optic with a focus spot of ø 3 mm and a homogenizing optic with a rectangular spot dimension of 8 × 8 mm(2). The laser processing was carried out using spot hardening at a heating-/cooling rate of 1000 K/s and was controlled via pyrometric temperature measurement using a control temperature of 1150 °C. The set-up being established during the measuring campaign allowed for this first realization data collection rates of 10Hz. The data evaluation procedure applied enables the separation of thermal from elastic strains and gains unprecedented insight into the laser hardening process.

Dual-wavelength high-power diode laser system based on an external-cavity tapered amplifier with tunable frequency difference

A dual-wavelength high-power semiconductor laser system based on a tapered amplifier with double-Littrow external cavity is demonstrated around 800 nm. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 10.0 THz. To our knowledge, this is the broadest tuning range of the frequency difference from a dual-wavelength diode laser system. The spectrum, output power, and beam quality of the diode laser system are characterized. The power stability of each wavelength is measured, and the power fluctuations of the two wavelengths are almost of opposite phase. The simultaneous emission of the two wavelengths is verified by a sum-frequency generation experiment in a bismuth triborate nonlinear crystal.

Laser-assisted surface engineering of thin film electrode materials for lithium-ion batteries

ABSTRACTElectrode thin films made of LiCoO2, Li-Mn-O and SnO2 were synthesized by rf magnetron sputtering on silicon and stainless steel substrates. In order to increase the active surface direct laser structuring methods using ns- and ps-laser sources were applied. A laser system operating at a wavelength of 248 nm with a pulse length of 4-6 ns and repetition rates up to 500 Hz enabled the formation of high aspect ratio micro- and sub-micron structures with feature sizes down to less than 400 nm. Subsequent to the laser structuring process, laser annealing of LiCoO2 and Li-Mn-O was performed in order to achieve an appropriate crystalline phase which shows improved electrochemical cycling performance. Laser annealing was applied via a high power diode laser system operating at a wavelength of 940 nm. In case of LiCoO2 the high temperature phase was obtained through laser-annealing while for Li-Mn-O the spinel phase was formed. For both LiCoO2 and Li-Mn-O thin films appropriate annealing parameters were temperatures of up to 680 °C and an annealing time of 100 s.

4140 耐熱構造試験用半導体レーザの加熱特性評価(S76-1 宇宙構造・材料(1),S76 宇宙構造・材料)

4140 耐熱構造試験用半導体レーザの加熱特性評価(S76-1 宇宙構造・材料(1),S76 宇宙構造・材料)

3D GAS FLOW VISUALIZATION IN OXYGENATOR OF HEART LUNG MACHINE WITH HYPERPOLARIZED 3He GAS MRI

It is important to know the flow path of oxygen and blood insideoxygenator. However, there is no way to observe the actual gas flow inside the oxygenator. In this study, we utilized the novel hyperpolarized(HP) 3He gas MRI technique to monitor the gas flowing through theoxygenator. Hyperpolarization of the noble gas nuclei is achieved byspin exchange with rubidium atoms that have been optically pumpedinto one electronic spin state with the use of circularly polarized light from a high-power diode laser system. The HP 3He gas was then inducedin to the oxygenator (HPO-2OH-C, Senko medical instrument) and wasimaged using a 1.5T clinical MRI system. The MRI imaging parameters included TR=75ms, TE=1.3ms, slice thickness 10mm, matrixsize = 256×256, and FOV=30×30cm. Both projection images and multislice images were obtained. The images were reconstructed to generate 3D images using in-house software. The projection images were created every 400msec after injection of 3He gas into the oxygenator. This method can observe the gas flow in the oxygenator with high spatial and temporal resolution. The signal intensity of the images directly reflects the concentration and distribution of the gas inside the fiber. Gas obstructions can be detected in the part of the hollow fiber where the fiber path changes. 3D rendered images of the gas flow were generated. The HP gas MRI method is the best analysis method for the visualization of gas flow in the oxygenator. We are presently working on visualization of the transition of the gas into the liquid blood phase.

Recubrimientos superficiales con láseres de diodos de alta potencia

Nowadays, high power diode laser systems are available in the market. These systems, based on arrays of small diode lasers, can achieve more than 1 kW of output power and are currently offering new possibilities in the field of laser material processing where CO 2 and Nd:YAG lasers were used up to the present. The results obtained in some materials cladding based on cobalt and nickel alloys as additional materials is presented. The instrumental set-up used in these experiments are described.

Fabrication of two-sided anamorphic microlenses and direct coupling of tapered high-power diode laser to single-mode fiber

An anamorphic microlens has been developed to couple a tapered unstable-resonator laser directly to a single-mode fiber, and has demonstrated capability for simple, compact and efficient high-power diode laser systems. Far high collection and coupling efficiencies, the refractive microlens has been fabricated by utilizing both sides of a GaP substrate, in which the first side was used to remove the astigmatism of the laser output and the second side to focus the beam to a spot size comparable to the fiber mode. The microlenses have been accurately formed by using a recent technique of mass-transport smoothing of etched multimesa preforms. Initial fiber-coupling experiments showed powers as high as 360 mW at the fiber output, and coupling efficiency as high as 29.5% has been measured at a lower power.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>