High Laser Output Research Articles

Research on all-solid-state blue lasers

Blue lasers have many important applications such as high-density optical data storage, biological and medical diagnostics, color displays, and submarine laser imaging and communication. High efficiency, high brightness and compactness all-solid-state blue lasers have attracted much attention for their merits. In this paper, four main ways for achieving all-solid-state blue lasers are reviewed and compared in detail, such as the semiconductor laser, the frequency-doubling of the semiconductor laser, the up-conversion blue laser, the nonlinear optical frequency conversion of Nd3+-doped or optical parametric oscillating lasers and so on. Results show that the nonlinear optical frequency conversion of the Nd3+-doped lasers is a potential way to realize a high power, high efficiency cw or pulsed blue laser output.

Prototype of a high-power, high-energy industrial XeCl laser

We discuss the results of fabrication and experimental study of a high-power excimer XeCl laser for industrial applications. Compactness of the laser is achieved by the employment of a laser chamber based on a ceramic tube made of . High laser output energy is obtained using a wide-aperture (up to ) volume discharge with pre-ionisation by a creeping discharge. The pre-ionisation is realised through a semi-transparent electrode by the UV radiation of a creeping discharge in the form of uniform plasma sheet on a surface of a plane sapphire plate. The operating lifetime of the gas mixture amounts to at a stabilised average laser power of . The results obtained demonstrate real prospects for developing a new class of excimer XeCl lasers with an average power of .

Compositional dependence of room-temperature Stark splitting of Yb^3+ in several popular glass systems

The room-temperature Stark splitting properties of Yb3+ are practical and valuable for lasers because the working temperature of the gain media intensively increases with the laser output. In this Letter, the room-temperature Stark splitting properties of Yb3+ in several popular laser glasses are contrastively studied. Yb3+-doped germanate (Ge), borate (B), silicate (Si), bismuthate (Bi), tellurite (Te), and fluorophosphate (FP) glasses exhibit large Stark splitting and tend to operate close to the quasi-four-level scheme, whereas phosphate (P) glass shows the weakest Stark splitting and tends to operate close to the quasi-three-level one. Due to the low thermal conductivity of the glass matrix, Yb3+-doped P glass suffers from serious thermal problems and is difficult to achieve high laser output. The Stark splitting is also used to estimate the crystal-field strength of glass hosts and local Yb3+ ligand asymmetry degree. The results show that P glass shows weaker crystal-field effect and lower Yb3+ ligand asymmetry than Ge, Si, and B glasses.

Solid-state grain growth of garnet single crystals of complex composition

Various (Nd-doped (Y,Gd,La,Lu)3(Sc,Al)5O12) garnets were reproducibly grown from a Nd-doped (Y,Gd,La,Lu)3(Sc,Al)5O12 polycrystalline precursor. Single crystals were grown through controlled abnormal grain growth at temperatures between 1750°C and 1850°C. Nd-doped (Y,Gd,La,Lu)3(Sc,Al)5O12 powder was prepared using the co-precipitation method, and single crystals were fabricated by the conversion of polycrystalline material. The phase identification of the specimens was performed using XRD and X-ray double crystal rocking curve (DCRC) analysis. The absorption spectra, fluorescence spectra, and fluorescence lifetimes of samples excited using an 808nm laser diode (LD) were also measured. The fluorescence lifetime of Nd-doped (Y,Gd,La,Lu)3(Sc,Al)5O12 single crystals is longer than that of Nd:YAG; a prolonged fluorescence lifetime helps to achieve a high laser output power. In short, we can fabricate complex mixed-garnet single crystals using the solid-state single-crystal conversion (SCC) method.

The Nd:YAG LIMAX® 120 high-output laser: local effects and resection capacity on liver parenchyma

Various technical options are available for the resection of liver metastases, including CUSA, Ultracision, water-jet, and stapler devices. It has been shown that new generation high-output lasers are suitable for the resection of lung metastases. The goal of the present study was to evaluate the local effects of laser application on liver parenchyma. Livers of freshly slaughtered pigs (N = 6) were analyzed. The handheld laser was vertically held in the clamp of a hydraulic machine and sharply focused on the liver surface. The diode pumped Nd:YAG laser LIMAX® 120 (Gebrüder Martin GmbH & Co. KG, Tuttlingen, Germany) moved evenly over the liver surface at speeds of 5, 10, and 20 mm/s. Laser outputs of 60 and 120 W were applied at every speed. Histological sections (hematoxylin and eosin (HE) staining) of the extension area of vaporization and coagulation were analyzed by the use of the ImageJ software. In addition, the area of the liver parenchyma cut by the laser within 1 min was measured. The vaporized zone appeared wedge-shaped after histological section, whereas the area of coagulation appeared radiated outward. At 10 mm/s and 60 W, the mean vaporization of the measured zone was 356.6 ± 3.9 μm in length. Superficial coagulation was observed at 20 mm/s laser speed, without effective resection. At 120 W and 5 mm/s working speed, the mean vaporization zone and the average width of coagulation were largest with 664.6 ± 5.9 and 375.6 ± 2.3 μm, respectively. The laser output power of 120 W allowed resection of an area of 6 ± 0.4 cm(2) of liver parenchyma within 1 min. The Nd:YAG Laser LIMAX® 120 might be an effective tool for liver parenchyma dissection when it is applied at maximum output (120 W) and at a constant working speed of 5 mm/s.

High-Power Distributed Feedback Terahertz Quantum Cascade Lasers

Single-mode operation of distributed feedback (DFB) terahertz quantum cascade lasers based on metal-stripe surface grating structure is reported. Strong DFB coupling and low waveguide loss conditions are obtained while maintaining a high laser output power. A record high edge-emitting optical power of 57 mW, ~ 96.2 μm at 10 K together with a well-shaped far-field pattern is presented. Reliable dynamic single-mode emission at all injection currents and operating temperatures is realized with a side-mode suppression ratio .

OP-31 The Nd:YAG LIMAX® 120 high-output laser: local effects and resection capacity on liver parenchyma

OP-31 The Nd:YAG LIMAX® 120 high-output laser: local effects and resection capacity on liver parenchyma

The Measurement of Singlet Oxygen Production in an Experimental Tongue Cancer Model as an Indicator for Photodynamic Therapy

Purpose: Photodynamic therapy (PDT) induced singlet oxygen (1O2) can cause rapid necrosis of solid tumors. Using a new near-infrared photomultiplier tube system, the 1O2 production was monitored in realtime for HSC-3 tongue cancer cells and in vivo tissue, and the relationship between the 1O2 production and anti-tumor effects was investigated. Experimental Design: Using 5-aminolevulinic acid (5-ALA), 1O2 generation was induced with a variety of laser parameters (fluence and irradiation) in vivo. During this time, tumor death was evaluated. Based on the 1O2 production, the optimal irradiation conditions and the long-term outcome were investigated on a subcutaneous tongue cancer model over 90 days. Methods and Results: The 1O2 production showed a strong correlation with the laser output in a dose-dependent manner. At high laser output, the 1O2 levels were high and caused gradual but strong antitumor effects, whereas at low laser outputs, the 1O2 levels were low and the anti-tumor effects were rapid but superficial. We then performed PDT in an experimental tongue cancer model at an irradiance lower than 150 mW/cm, which was identified in the first part of the study as the optimal irradiance value based on the 1O2 production. Within the 90 days post PDT, PDT-induced hemorrhagic necrosis was observed in 8 mice out of 10 within 5 days. In the other 2 mice, no sign of necrosis was seen until 25 days after PDT. The tumor volume of the PDT group continued to decline except for 2 mice which showed some slight growth over 70 days after PDT. In the control group, tumor size increased dramatically over 70 days. Conclusions: The present studies established 1O2 levels as an indicator for optimal irradiation during PDT, and showed a relationship between the 1O2 production and the photodynamic effects. Although 5ALA mediated PDT showed a strong anti-tumor effect on larger subcutaneous tongue tumors, it might be more effective for small tumors of oral cavity.

Experimental study on coherent beam combination of fiber amplifiers using adaptive power-in-the-bucket cost function

Beam combination (BC) of fiber amplifiers based on master-oscillator-power-amplifier configuration is an outstanding way to generate high power and high beam quality laser output, where the tip/tilt aberrations among beamlets are considered as a serious influence factor to BC effects. In this paper, a new tip/tilt control method based on adaptive power-in-the-bucket (PIB) cost function is proposed to solve the problem of restricted tip/tilt correcting value in current BC systems. Experimental setup of coherent BC of two-channel 2 W fiber amplifier array is established. Home-made piezoelectric-ring fiber-optic phase-modulator and adaptive fiber-optics collimator are employed to correct piston-and tip/tilt-type aberrations, respectively. The feasibility of proposed tip/tilt control method using adaptive-PIB is demonstrated and nice effect of coherent BC is achieved.

Nd:YAGレーザーがヒト歯肉線維芽細胞に与える影響について

This study was performed in order to investigate the effects of Nd:YAG laser irradiation on human gingival fibroblasts (Gin-1), as represented by cell proliferation activity rate and TGF-β1 and Type I collagen production rate, as well as HSP47 expression.Gin-1 cells were irradiated for 10 seconds at laser outputs of 2W (5pps/400mJ, 100pps/20mJ) and 7.2W (40pps/180mJ, 90pps/80mJ), at irradiation distances of 10mm or 20mm. Culture supernatant was recovered after 3 and 5 days of culture following laser irradiation and investigated for cell proliferation rate (modified MTT), and TGF-β1 and Type I collagen production rate (ELISA method). Gin-1 was also subjected to immunofluorescent staining after 3 hours of culture following laser irradiation, and observed for HSP47 expression by confocal laser scanning microscopy.On the 5th day of culture, both of the groups irradiated by 2W at 10mm exhibited significantly higher cell proliferation rates than controls, and on the 3rd day of culture the group irradiated by 7.2W (90pps/80mJ) at 10mm exhibited significantly higher TGF-β1 production rates than controls. Among the 10mm irradiation groups on the 3rd day, both of the 7.2W groups exhibited significantly higher Type I collagen production rates than controls. Intracytoplasmic HSP47 expression was found in all groups.Thus, high-output laser irradiation with an increased irradiation distance exerts a cell activating effect without harmful heating, similar to that of low-output laser irradiation.

Simulations of conjugate Dammann grating based 2D coherent solid-state laser array combination

Conjugate Dammann grating based coherent beam combing technique is an efficient way of combining phase-locked laser array into one high-power high beam-quality laser output. In this paper, this technique is applied to the combination of two-dimensional phase-locked array of solid state laser beams. Square apertures that could increase the areal fill factor of 21.5% are adopted. Numerical and experimental simulations of the combinations of 4×4 and 5×5 2D coherent laser arrays are carried out. The influences of manufacturing and positioning errors of the conjugate Dammann gratings to the beam combining efficiency are also discussed in detail.

Ultra-fast photo-patterning of hydroxamic acid layers adsorbed on TiAlN: The challenge of modeling thermally induced desorption

Long-chain n-alkyl terminated hydroxamic acids (HA) are used for the modification of titanium aluminum nitride (TiAlN) surfaces. HA coatings improve the hydrophobicity of this wear resistant and industrially relevant ceramic. Therefore, HAs with different structural properties are evaluated with respect to their wear resistance and their thermal desorption properties. In order to find new coatings for rewritable offset printing plates, the changes in the surface polarity, composition, and morphology are analyzed by contact angle measurements, X-ray photoemission spectroscopy (XPS), and scanning force microscopy (SFM), respectively. The results are referenced to the strongly bonding molecule n-dodecyl phosphonate (PO11M), which has been used for surface hydrophobization before but proved difficult to remove due to the high laser outputs required for thermal desorption. It is found that for certain HAs, an equally good hydrophobization compared to PO11M can be achieved. Contact angles obtained for different hydroxamic acid coatings can be correlated to their modes of adsorption. Only for selected HA species, resistance to mechanical wear is sufficient for further investigations. Photo-patterning of these hydroxamic acid layers is achieved using a high energy IR laser beam at different energy inputs. Fitting of the obtained data and further evaluation using finite element analysis (FEM) calculations reveal significantly reduced energy consumption of about 20% for the removal of a specific hydroxamic acid coating from the ceramic surface compared to PO11M.

Theoretical analysis of characteristics for 2 μm Tm3+:Ho3+ co-doped silica fiber laser pumped by a 1550 nm fiber laser

We established a theoretical model of 2μm Tm3+:Ho3+ co-doped silica fiber laser pumped by a 1550nm fiber laser based on the rate-equation theory and performed the numerical simulation using Runge–Kutta algorithm and Newton–Raphson algorithm. The intracavity power distributions of both pump and laser of the Tm3+:Ho3+ co-doped silica fiber laser based on the Tm3+:Ho3+ co-doped silica fiber supplied by the National Optics Institute in Canada (NOIC) were obtained. The effects of the output reflectivity R4(λs) at the output laser wavelength λs and the concentrations of Tm3+ and Ho3+ in the fiber on laser output performance were analyzed. In order to achieve a high laser output power, the optimal R4(λs) of 0.13 was verified and the optimal Tm:Ho ratio of 1:2.4 was proposed. Finally, better output performance for the fiber laser based on the optimized Tm3+:Ho3+ co-doped silica fiber was obtained than the laser using the fiber supplied by the NOIC. This theoretical model and numerical simulation results will guide the fabrication of 2μm Tm3+:Ho3+ co-doped all-fiber lasers pumped by 1600-nm-band (1500–1750nm) Er3+:Yb3+ co-doped silica fiber lasers.

High efficiency and good beam quality of electro-optic, cavity-dumped and double-end pumped Nd:YLF laser

In this paper, we describe a Nd:YLF laser based on high-speed RTP electro-optical cavity dumping technique. Two home-made 150 W fiber pump modules are used from both sides to pump Nd:YLF crystal. Coupling systems are the key elements in end-pumped solid-state lasers, the aberrations of which greatly affect the efficiency of the lasers. In order to get high efficient and good quality laser output, the optical software ZEMAX is used to design a four-piece coupling system. When the pumped energy is 32 mJ at the repetition rate of 1 Hz, the output energy is 6.5 mJ with 2.5 ns pulse width. When the pumped energy is 13.1 W at the repetition rate of 200 Hz, the output energy is 2.2 W with small M 2 factor where M 2 is 1.04, and M 2 is 1.05, and the light-light conversion efficiency is up to 16.8%.

Inverter power supply and control system for high pulse energy laser shock processing

In order to meet high pulse laser output, the laser shock power supply based on insulated gate bipolar transistor (IGBT) inverter technology, constant current-constant voltage charger mode, high voltage pulse spark, and high pulse current discharger technology is designed. The master oscillator stage and two amplifier stages for xenon flash lamp spark and discharge circuits are designed in this power supply. The voltage of energy storage capacitors can be adjusted from 1 000 to 3 000 V. A variety of measures, such as FREE and Q-switch mode, trigger signal delay, water confining layer control, cooling water control are provided for laser shock processing technology optimization.

Experimental study of SBS suppression and coherence property of 1064 nm high power multi-tone fiber amplifier

Seeding high power fiber amplifier employing multi-tone fiber laser is an effective approach to suppress stimulated Brillouin scattering (SBS). In this paper, a two-stage 1064 nm high power fiber amplification system was set up. Single-, two- and three-tone fiber lasers were employed. SBS threshold powers and maximum output powers of the multi-tone cases are enhanced compared with the single-tone case. The multi-tone amplifiers also show comparable optical-to-optical efficiency to the single-tone amplifier. To demonstrate and validate coherence property of the two multi-tone fiber amplifiers, the output laser beams of the amplifiers were self-interfered in our self-made coherent beam combining system. The laser beams of the multi-tone cases showed good coherence property comparable to the single-tone case, which implied that the high power output laser light of the multi-tone fiber amplifiers could be used for coherent beam combining.

Laser remelting of alumina tile surfaces: corrosion testing in aqueous solution

Laser treatment of alumina surfaces in a nitrogen gas environment was carried out and the corrosion response of the resulting surfaces is examined. The corrosion tests were carried out using 5% NaCl solution for seven days, with continuous steering by a magnetic stirrer. Metallurgical and morphological changes in the laser irradiated region are examined using the scanning electron microscope, optical microscope, X-ray diffraction. It was found that formation of nitride (AlN) compounds was evident with a compact and dense structure formed in the laser irradiated region. Moreover, a few shallow pit sites are evident around the crack tips after the static corrosion tests, especially at a high laser output power.

Beam structure of a diode-side-pumped Nd:YVO4 slab laser

The beam spatial structure of a diode-side-pumped Nd:YVO4 slab laser with grazing-incidence bounce geometry is studied. It is found how the mode structure changes with changing the cavity parameters in the cw and active Q-switching regimes. The parameters that allow one to improve the output beam quality retaining high output laser power are found.

Partial laser and gas nitriding of titanium components

Abstract Gas nitriding and laser gas nitriding processes were studied to produce thick and well adhering nitride layers on titanium alloys. A multitude of process parameters have been varied for the nitriding of Ti-6Al-4V substrates. The nitride layers were investigated with optical and electron microscopy, micro hardness testing and glow discharge optical emission spectroscopy. Gas nitriding resulted in strongly adherent nitride layers of up to 5 µm in thickness. Laser gas nitriding with high laser output resulted in very thick (> 500 µm) nitride layers with excellent surface adhesion. A partial melting of the surface during the process altered the surface contour; hence, a reshaping of the component may be necessary. A melting of the substrate surface was avoided through laser gas nitriding with low laser output and additional cooling. However, the up to 100 µm thick nitride layers showed cracks at the interfaces to the substrate.

Diffractive multi-beam surface micro-processing using 10 ps laser pulses

A high repetition rate picosecond laser system is combined with a spatial light modulator (SLM) for diffractive multiple beam processing. The effect of the zero order beam is eliminated by adding a Fresnel zone lens (FZL) to defocus the un-diffracted beam at the processing plane. Chromatic dispersion, which is evident with a large bandwidth femtosecond pulses leading to the problem of distorted hole shape is eliminated due to the much narrower spectral bandwidth, ∼0.1 nm at 10 ps pulselength, resulting in highly uniform intensity spots, independent of diffraction angle. In addition, high-throughput processing is demonstrated by combining the high power laser output, 2.5 W at λ ≈ 1064 nm and fast repetition rate, f ≈ 20 kHz with P > 1.2 W diffracted into 25 parallel beams. This has the effect of creating an “effective” repetition rate of 500 kHz without restrictive scan speeds.