Showing papers on "Laser power scaling published in 2004"
TL;DR: A highly-efficient cladding-pumped ytterbium-doped fiber laser generating 1.36 kW of continuous-wave output power at 1.1 mum with 83% slope efficiency and near diffraction-limited beam quality is demonstrated.
Abstract: We have demonstrated a highly-efficient cladding-pumped ytterbium-doped fiber laser generating 1.36 kW of continuous-wave output power at 1.1 µm with 83% slope efficiency and near diffraction-limited beam quality. The laser was end-pumped through both fiber ends and showed no evidence of roll-over even at the highest output power, which was limited only by available pump power.
887 citations
TL;DR: The demonstration of the first silicon Raman laser using a silicon waveguide as the gain medium and has a clear threshold at 9 W peak pump pulse power and a slope efficiency of 8.5%.
Abstract: We report the demonstration of the first silicon Raman laser. Experimentally, pulsed Raman laser emission at 1675 nm with 25 MHz repetition rate is demonstrated using a silicon waveguide as the gain medium. The laser has a clear threshold at 9 W peak pump pulse power and a slope efficiency of 8.5%.
823 citations
TL;DR: In this article, the effects of processing conditions, such as laser power, scan speed, powder feed rate, etc. on the microstructure of the build have been assessed and it has been found that Ti-6Al-4V is very susceptible to the formation of columnar grains during laser deposition.
372 citations
TL;DR: In this article, the first experimental demonstration of an end-pumped Cs laser using a Ti:sapphire laser for pump excitation is presented, and a discussion is given on power scaling diodepumped alkali lasers, indicating a potential efficiency advantage over power-scaled diode-pump solid-state lasers.
Abstract: End-pumped alkali vapor lasers excited on their D2 transition and lased on their D1 transition offer a pathway to high average power that potentially competes with diode-pumped solid-state lasers in many applications that require cw or quasi-cw laser operation. We report on the first experimental demonstration of an end-pumped Cs laser using a Ti:sapphire laser for pump excitation. Detailed experimental and model results are presented that indicate our understanding of the underlying physics involved in such systems is complete. Using an extrapolation of our developed model, a discussion is given on power scaling diode-pumped alkali lasers, indicating a potential efficiency advantage over power-scaled diode-pumped solid-state lasers.
221 citations
TL;DR: In this paper, an Ag target was irradiated with a 532-nm laser beam in pure water to synthesize very small spherical particles with a typical size of 2-5 nm.
Abstract: We have successfully produced silver nanoparticles by irradiating an Ag target with a 532-nm laser beam in pure water. By working with high laser power and small spot sizes, we were able to synthesize very small spherical particles with a typical size of 2–5 nm. The influence of the beam spot size, the laser power, and the ablation time were studied, and the possible mechanisms of particle formation are discussed.
188 citations
TL;DR: Waveguides manufactured with the 520-nm radiation from a frequency-doubled, diode-pumped, cavity-dumped Yb:glass laser operating at a 166-KHz repetition rate, with a 300-fs pulse duration are demonstrated.
Abstract: Laser action is demonstrated in a 20-mm-long waveguide fabricated on an Er:Yb-doped phosphate glass by femtosecond laser pulses. An output power of 1.7 mW with approximately 300 mW of pump power coupled into the waveguide is obtained at 1533.5 nm. Waveguides are manufactured with the 520-nm radiation from a frequency-doubled, diode-pumped, cavity-dumped Yb:glass laser operating at a 166-KHz repetition rate, with a 300-fs pulse duration.
184 citations
TL;DR: In this article, a systematic experimental examination of the cavity enhanced Raman spectroscopy of water droplets is presented, in particular, the influences of laser power and illumination geometry, ionic strength and the presence of a second Raman active scatterer, nitrate, on the shape of the water Raman band are explored.
Abstract: Micron-sized liquid droplets exhibit unique optical properties, including lower threshold energies for non-linear optical processes than are observed in the bulk liquid phase. Whispering gallery modes (WGMs) and cavity quantum electrodynamics lead to cavity enhancement of fluorescence and Raman scattering at wavelengths commensurate with WGMs. The principles of cavity enhanced droplet spectroscopy will be reviewed, along with the major developments in the field over two decades. The prospect of applying cavity enhanced techniques in the simultaneous determination of droplet size and composition is discussed. A systematic experimental examination of the cavity enhanced Raman spectroscopy of water droplets is presented. In particular, the influences of laser power and illumination geometry, ionic strength and the presence of a second Raman active scatterer, nitrate, on the shape of the water Raman band are explored. Prospects for applying cavity enhanced techniques to studies of aerosol dynamics are also discussed.
166 citations
TL;DR: The microscopic morphology and distribution of tungsten carbide (WC) particles in a laser-clad Ni-WC composite coatings were characterized by scanning electron microscopy (SEM).
162 citations
01 Dec 2004-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, a mathematical model is developed to simulate the coaxial laser-cladding process with powder injection, which includes laser- substrate, laser-powder, and powder-substrate interactions.
Abstract: Laser cladding is one of the material additive manufacturing processes used to produce a metallurgically bonded deposition layer. To obtain a high-quality resulting part, a deep understanding of the underlying mechanisms is required. In this article, a mathematical model is developed to simulate the coaxial laser-cladding process with powder injection, which includes laser- substrate, laser-powder, and powder-substrate interactions. The model considers most of the associated phenomena, such as melting, solidification, evaporation, evolution of the free surface, and powder injection. The fluid flow in the melt pool, which is mainly driven by Marangoni shear stress as well as particle impinging, together with the energy balances at the liquid-vapor and the solid-liquid interfaces, are investigated. Powder heating and laser power attenuation due to the powder cloud are incorporated into the model in the calculation of the temperature distribution. The influences of the powder injection on the melt pool shape, penetration, and flow pattern are predicted through the comparison for the cases with powder injection and without powder injection. Dynamic behavior of the melt pool and the formation of the clad are simulated. The effects of the process parameters on the melt pool dimension and peak temperature are further investigated based on the validated model.
161 citations
TL;DR: This work reports, for the first time to the authors' knowledge, diode-pumped cw laser oscillation of Pr3+:LiYF4 in the red spectral range.
Abstract: We report, for the first time to our knowledge, diode-pumped cw laser oscillation of Pr3+:LiYF4 in the red spectral range. The pump power is provided by a GaN laser diode emitting a maximum output power of 25 mW at a wavelength of approximately 442 nm. The Pr3+ laser emits 1.8 mW of output power at a 639.7-nm wavelength. Threshold pump power and slope efficiency in a nonoptimized setup are determined to be 5.5 mW and 24%, respectively.
149 citations
TL;DR: This is the first report of a single-frequency DFB fiber laser that uses thulium as the amplifying medium and the lasing wavelength is the longest demonstrated with DFB Fiber lasers and yet is among the shortest obtained forThulium-doped silica fiber lasers.
Abstract: We have successfully demonstrated a single-frequency distributed-feedback (DFB) thulium-doped silica fiber laser emitting at a wavelength of 1735 nm. The laser cavity is less than 5 cm long and is formed by intracore UV-written Bragg gratings with a phase shift. The laser is pumped at 790 nm from a Ti:sapphire laser and has a threshold pump power of 59 mW. The laser has a maximum output power of 1 mW in a single-frequency, single-polarization radiation mode and is tunable over a few nanometers. To the best of the authors’ knowledge, this is the first report of a single-frequency DFB fiber laser that uses thulium as the amplifying medium. The lasing wavelength is the longest demonstrated with DFB fiber lasers and yet is among the shortest obtained for thulium-doped silica fiber lasers.
TL;DR: In this paper, a spiral-shaped microcavity heterojunction laser diode fabricated with InGaN multiple quantum wells is demonstrated to operate under current injection conditions and emit unidirectionally.
Abstract: A spiral-shaped microcavity heterojunction laser diode fabricated with InGaN multiple quantum wells is demonstrated to operate under current injection conditions and emit unidirectionally. Room-temperature laser operation was achieved for microcavity disk radii ranging from 50 to 350 μm and threshold current densities as low as 4.6 kA/cm2. Unidirectional laser emission is clearly revealed in the far-field pattern with the lateral divergence angle ranging from 60° to 75°. Output power of more than 25 mW was obtained for emission wavelengths near 400 nm.
Patent•
11 Aug 2004
TL;DR: In this paper, the authors presented an object of the present invention to provide a laser irradiation apparatus which can form a linear beam spot with a short optical path length, and reduce displacement of a condensing point at opposite ends in a direction of its line.
Abstract: It is an object of the present invention to provide a laser irradiation apparatus which can form a linear beam spot with a short optical path length, form a linear beam spot being long in a long-side direction, and reduce displacement of a condensing point at opposite ends in a direction of its line. In a laser irradiation apparatus having an optical system for shaping a laser beam emitted from a laser oscillator into a linear beam spot having a long-side direction and a short-side direction, the optical system includes a long-side direction condensing cylindrical lens disposed between a first short-side direction condensing cylindrical lens and a second short-side direction condensing cylindrical lens. Displacement of a position of a homogeneous plane is generated by the long-side direction condensing cylindrical lens so that a distance from the homogeneous plane to the second short-side direction condensing cylindrical lens is constant not depending on a field angle.
TL;DR: A high-power tandem-pumped Ho3+, Pr3+-doped ZBLAN fiber laser is demonstrated, which allows single-transition output and saturation of the output is avoided with Pr3+.
Abstract: A high-power tandem-pumped Ho3+, Pr3+-doped ZBLAN fiber laser is demonstrated. Using the free-running 1100-nm output from a diode-cladding-pumped Yb3+-doped silica fiber laser as the pump source, a maximum output power of 2.5 W was generated at a slope efficiency of 29% after the threshold of approximately 30 mW was reached. Saturation of the output is avoided with Pr3+ codoping, which allows single-transition output. The center wavelength of the output was 2.86 microm and the bandwidth at maximum power was approximately 15 nm.
TL;DR: The entire pump power for the nonlinear conversion stages is provided by a single laser oscillator without any amplifier stages, and all nonlinear crystals except one are critically phase matched at room temperature.
Abstract: We present a red-green-blue laser source with average powers of 8 W in the red, 23 W in the green, and 10.1 W in the blue. The entire pump power for the nonlinear conversion stages is provided by a single laser oscillator without any amplifier stages. Our system does not require any synchronized cavities, and all nonlinear crystals except one are critically phase matched at room temperature.
TL;DR: In this paper, the design and performance of cladding-pumped silica fiber lasers with high continuous-wave output powers and broad wavelength tunability in the 1, 15, and 2 µm spectral ranges were described.
TL;DR: In this paper, the thermal and rheological properties of nanocomposite powders were compared with standard polyamide 6 and clay nanoparticle/polyamide 6 composite for applications in the selective laser sintering (SLS) process.
TL;DR: In this article, an overview of the development status and plans of extreme ultraviolet (EUV) light sources at XTREME technologies, a joint venture of Lambda Physik AG, Gottingen and JENOPTIK LOS GmbH, Jena, Germany is presented.
Abstract: This paper gives an overview of the development status and plans of extreme ultraviolet (EUV) light sources at XTREME technologies, a joint venture of Lambda Physik AG, Gottingen and JENOPTIK LOS GmbH, Jena, Germany. Results for gas discharge-produced plasma (GDPP) and laser-produced plasma (LPP), the two major technologies in EUV sources, are presented.The GDPP EUV sources use the Z-pinch principle with efficient sliding-discharge pre-ionization. First prototypes of commercial gas discharge sources with an EUV power of 35 W in 2π sr have already been integrated into EUV microsteppers. These sources are equipped with a debris-filter which supports an optics lifetime exceeding 100 million pulses at 1 kHz repetition rate. The same lifetime was achieved for the components of the discharge system itself.The progress in the development of high-power discharge sources based on xenon resulted in an EUV power of 200 W into a 2π sr solid angle, in continuous operation, at 4.5 kHz repetition rate, by implementation of porous-metal cooling technology. The available intermediate focus (IF) power is 22 W taking into account experimentally verified losses in a 1.8 sr source collector module. The usable IF power depends on the etendue of the optical system of the EUV scanner. For the current size of the EUV emitting plasma the etendue acceptance factor may be below 0.5. The currently usable IF power with 1.8 sr collector mirror may therefore be about 10 W.Z-pinch discharge sources with Sn as the emitter have been developed as a more efficient alternative to xenon fuelled sources. Tin sources showed a conversion efficiency (CE) that was double that of xenon. EUV power of 400 W in 2π sr has been generated at only 4.5 kHz repetition rate. The available IF power is 44 W. Estimates evaluating the tin source performance reveal the potential for achieving high-volume manufacturing (HVM) power specification by using existing technology.Because of their small plasma size and the rather simple thermal management in the EUV generator the LPP EUV sources are investigated as alternatives to GDPP sources to achieve sufficient power for HVM with EUV lithography. These sources use xenon-jet target systems and high-power pulsed lasers as plasma excitation drivers developed at XTREME technologies. The maximum CE from laser power into EUV in-band power is 1.0% into a solid angle of 2π. Experimentally, 7 W EUV radiation is generated at 13.5 nm in a 2π sr solid angle with 0.7 kW laser power on the target. The small source volume of <0.5 mm diameter will allow large collection angles of 5 sr. The corresponding usable IF power is estimated to be 2.3 W. With the full power of the installed 1.2 kW laser driver 10 W EUV power in 2π sr is expected. LPP sources with tin targets are estimated to achieve nearly 10 W IF power with existing driver laser technology.GDPP and LPP sources still compete for the technology of HVM sources for EUV lithography. Each of these technologies has its challenges. The optimization potential of the etendue of the optical system of EUV scanners will certainly influence any decision for a HVM source technology.
TL;DR: Results of diode-pumped cw laser operation of an Yb3+:CaF2 single crystal are reported for what is to the authors' knowledge the first time, showing the great potential of Yb 3+: CaF2 as an amplifier medium for femtosecond pulses.
Abstract: Results of diode-pumped cw laser operation of an Yb3+:CaF2 single crystal are reported for what is to our knowledge the first time. With a 5-at.% Yb3+ -doped sample we obtained 5.8-W output power at 1053 nm for 15 W of incident power at 980 nm. The laser wavelength could be tuned from 1018 to 1072 nm, and a small-signal gain as high as 1.8 was achieved, showing the great potential of Yb3+:CaF2 as an amplifier medium for femtosecond pulses.
01 Feb 2004-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, a study of laser energy transfer efficiency, melting efficiency, and deposition efficiency has been conducted for the laser-engineered net-shaping process (LENS) for H-13 tool steel and copper powder deposits.
Abstract: A study of laser energy transfer efficiency, melting efficiency, and deposition efficiency has been conducted for the laser-engineered net-shaping process (LENS) for H-13 tool steel and copper powder deposits on H-13 tool steel substrates. This study focused on the effects of laser deposition processing parameters (laser power, travel speed, and powder mass flow rate) on laser beam absorption by the substrate material. Measurements revealed that laser energy transfer efficiency ranged from 30 to 50 pct. Laser beam coupling was found to be relatively insensitive to the range of processing parameters tested. Melting efficiency was found to increase with increasing laser input power, travel speed, and powder mass flow rate. A dimensionless parameter model that has been used to predict melting efficiency for laser beam welding processing was investigated for the LENS process. From these results, a semiempirical model was developed specifically for the LENS processing window. Deposition efficiency was also investigated and results show that under optimum processing conditions, the maximum deposition efficiency was approximately 14 pct. A semiempirical relation was developed to estimate deposition efficiency as a function of process efficiencies and LENS processing parameters. Knowledge of LENS process efficiencies measured in this study is useful to develop accurate heat flow and solidification models for the LENS process.
29 Dec 2004
TL;DR: In this paper, the authors describe the requirements and the development of a tabletop laser source for study of DIRCM techniques, which is able to generate wavelengths from 1.5 to 4 micron, at 2 micron they can generate between 400-550 mW, and in band II, from 3-4 micron we can generate 130-160 mW laser jam power.
Abstract: Countermeasures against heat seeking missiles require access to efficient laser sources, which should emit wavelengths at band I, II and IV. Efficient diode pumped solid-state lasers, combined with efficient non-linear wavelength shifters, allow the development of practical tuneable mid-IR countermeasure sources. The paper describes the requirements and the development of a tabletop laser source for study of DIRCM techniques. Jamming laser systems must be able of creating pulse sequences in the frequency range between 100 Hz and 10,000 Hz, including the capability to mix and sweep the jam frequency. A Nd:YVO4 pump laser with maximum pump power of 3 Watt and pulse length of 10 ns, and a maximum modulation frequency of 100 kHz was selected. A linear single resonant OPO cavity with 30 mm long, 1mm thick PPLN crystals was build. With the tabletop laser system we were able to generate wavelengths from 1.5 to 4 micron. In band I, at 2 micron we can generate between 400-550 mW, and in band II, from 3-4 micron we can generate 130-160 mW laser jam power. The beam quality (M2) is approximately 2.5. The power efficiency for the idler was 8.8%, while the slope power efficiency was 15%. Jam patterns are generated by use of an acousto-optic modulator
TL;DR: Cryogenically cooled Yb:YAG is used to efficiently generate 165 W of near-diffraction-limited beam from a power oscillator with negligible thermo-optic effects.
Abstract: Thermo-optic distortions often limit the beam quality and power scaling of high-average-power lasers. Cryogenically cooled Yb:YAG is used to efficiently generate 165 W of near-diffraction-limited beam from a power oscillator with negligible thermo-optic effects. End pumped with 215 W of incident pump power from two diode modules, the laser has an optical–optical efficiency of 76%, a slope efficiency of 85%, and an M2 value of 1.02.
TL;DR: In this paper, a mathematical model for powder concentration distribution is developed and the results from it compared with an experimental investigation using optical and image analysis techniques, and the application of the model to the evaluation of nozzle geometry and the calculation of laser beam attenuation are demonstrated.
Abstract: Direct laser deposition is a solid freeform fabrication process that is capable of producing fully dense components with full structural integrity and is greatly enhanced by. the use of an onmidirectional coaxial powder nozzle to supply the build material. In order to optimize the technique, accurate control of the two critical operational parameters of material feed rate and incident laser power intensity is necessary. Both parameters are affected by the axial powder stream concentration between the nozzle and the deposition point. In this work, a mathematical model for the powder concentration distribution is developed and the results from it compared with an experimental investigation using optical and image analysis techniques. The two show good agreement. The application of the model to the evaluation of nozzle geometry and the calculation of laser beam attenuation are demonstrated.
TL;DR: In this paper, an infrared laser-trapping system was used to trap and manipulate individually dissolved single-walled carbon nanotubes in an aqueous solution using a microfluidic device.
Abstract: Optical trapping and manipulation of individually dissolved single-walled carbon nanotubes in an aqueous solution was demonstrated using an infrared laser trapping system. The trapping effect was attributed to the interaction between the electric field of the laser and the instantaneously induced dipole moments in individual nanotube molecules. Fluorescence microscopy and intensity measurements demonstrated that the amount of trapped nanotubes is dependent on the initial nanotube concentration, laser power, and irradiated volume of the laser beam. It was also demonstrated that an optical trap combined with a microfluidic device trapped and moved nanotubes in the fluid channel.
TL;DR: In this paper, a Ho:YAG laser end pumped by a cladding-pumped tunable Tm-doped silica-fibre laser operating at 1905-nm is reported.
Abstract: Highly efficient room-temperature operation of a Ho:YAG laser end pumped by a cladding-pumped tunable Tm-doped silica-fibre laser operating at 1905 nm is reported. Using a simple two-mirror resonator configuration, we obtained 6.4 W of unpolarized output at 2097 nm in a diffraction-limited TEM00 beam (with M2≈1.1) for 9.6 W of incident pump power, corresponding to a slope efficiency with respect to incident pump power of 80% and an optical-to-optical efficiency of 67%. Using a folded-resonator configuration incorporating a Brewster-angled glass plate, we obtained 5.8 W of linearly polarized TEM00 output, corresponding to an optical-to-optical efficiency of ∼60%. Due to low quantum defect heating, the depolarization loss due to thermally induced birefringence in the Ho : YAG crystal was <0.14% at the maximum available pump power, indicating that there is scope for further power scaling.
TL;DR: Single-mode operation of a Raman fiber laser based on a multimode fiber has been demonstrated for what is to the authors' knowledge the first time.
Abstract: Single-mode operation of a Raman fiber laser based on a multimode fiber has been demonstrated for what is to our knowledge the first time. Single-mode operation was achieved through the beam cleanup effect of stimulated Raman scattering in multimode fibers. The Raman laser, consisting of a 50‐µm-core multimode fiber and a multimode Nd:YAG laser pump, produced an output beam corresponding to the fundamental mode of the fiber. The measured beam quality factor M2 of the Raman laser beam was 1.66.
TL;DR: An efficient compact eye-safe laser at 1525 nm is presented by use of self-frequency Raman conversion in a diode-pumped actively Q-switched Nd:YVO4 1342-nm laser.
Abstract: An efficient compact eye-safe laser at 1525 nm is presented by use of self-frequency Raman conversion in a diode-pumped actively Q-switched Nd:YVO4 1342-nm laser. At an incident pump power of 13.5 W, the self-stimulated Raman laser produces 1.2 W of 1525-nm average output power at a repetition rate of 20 kHz. The corresponding peak power at 1525 nm is generally greater than 10 kW for repetition rates from 5 to 20 kHz.
TL;DR: In this paper, the capability of a 60W low power CO 2 -laser in cutting various nonmetallic materials has been studied and a theoretical model has been introduced that estimates the depth of the cut in terms of material properties and cutting speed.
TL;DR: In this article, a continuous-wave mid-infrared distributed feedback interband cascade laser was utilized to detect and quantify formaldehyde (H2CO) using quartz-enhanced photoacoustic spectroscopy.
Abstract: A novel continuous-wave mid-infrared distributed feedback interband cascade laser was utilized to detect and quantify formaldehyde (H2CO) using quartz-enhanced photoacoustic spectroscopy. The laser was operated at liquid-nitrogen temperatures and provided single-mode output powers of up to 12 mW at 3.53 μm (2832.5 cm-1). The noise equivalent (1σ) detection sensitivity of the sensor was measured to be 2.2×10-8 cm-1 W (Hz)-1/2 for H2CO in ambient air, which corresponds to a detection limit of 0.6 parts in 106 by volume (ppmv) for a 10 s sensor time constant and 3.4 mW laser power delivered to the sensor module.
Patent•
06 Dec 2004
TL;DR: In this article, a high power integrated fiber laser system includes cascaded amplifiers that utilize low numerical aperture fiber amplifiers, which is rugged and lightweight, and is used for high power laser systems.
Abstract: A high power integrated fiber laser system includes cascaded amplifiers that utilize low numerical aperture fiber amplifiers. The system is rugged and lightweight.