High-power Solid-state Lasers Research Articles

Fluorescence losses from Yb:YAG slab lasers.

We report on the distribution of fluorescence that can be emitted through the surfaces of a ytterbium-doped yttrium aluminum garnet (Yb:YAG) slab-shaped high-power solid-state laser. Slab shapes considered include parallel or antiparallel Brewster endfaced slabs and rectangular parallelepiped slabs. We treat cases in which all the faces of these slabs are in air, or with water or another coating on the largest faces. The fraction of the fluorescence emitted through each face, its distribution over that face, and the directions in which it travels are shown to be important to the design of high-power slab lasers.

Solid-State High-Energy Laser Weapons

Recent advances in semiconductor and solid-state lasers are being applied in the realm of laser weaponry. High-power diode-pumped solid-state lasers bring with them tough questions about the dangers of eye injury, both to soldiers and noncombatants.

Thermooptical compensation methods for high-power lasers

Thermally induced optical effects can be exploited to generate adaptive optical devices such as self-adjusting lenses. An adaptive lens in a resonator can be used to compensate for the thermal lens in a high-power solid-state laser rod (LR) and herewith significantly improve the beam quality and increase the output-power range of solid-state lasers. With suitable materials and an appropriate design of the compensating device, resonators with self-balancing thermal lenses can be developed. In this paper, we review the material requirements for a self-adaptive compensating element and discuss a selection of suitable materials (glasses, liquids and curing gels) and schemes to compensate for the thermal lens of a Nd:YAG LR. Finally, we present a very simple and promising design of a thermooptically self-compensated laser amplifier.

Results from the Stanford 10 m Sagnac interferometer

The design of a 10 m all-reflective prototype Sagnac interferometer with suspended optics is described and the experimental results are presented. It uses a polarization scheme to allow detection of the dark fringe on the symmetric port of the beamsplitter for optimal interference contrast. The necessary low-frequency response of the interferometer requires delay lines in the arms. To deal with the noise introduced by scattered light in the delay lines, a laser frequency sweep frequency shifts the scattered light so that it does not produce noise near zero frequency. This results in a shot-noise-limited phase sensitivity of Δϕ = 1.6 × 10−9 rad Hz−1/2 at frequencies as low as 200 Hz. Scaling this prototype to several kilometres with kilowatts of circulating power requires several technical improvements in high-power solid-state lasers, second harmonic generation and the fabrication of large mirrors, which are likely to be made in the next 10 years.

Continuous-wave diode-laser end-pumped Nd:YVO 4/KTP high-power solid-state green laser

A simple folded-cavity used for intracavity frequency-doubled Nd:YVO 4 laser was analyzed by transmission matrix and numerical calculation. We have selected a set of proper cavity parameters which can be used readily by operating at high power levels with low threshold, high efficiency, and wide dynamic operating range. 5.6-W TEM 00 green laser has been obtained at a 22-W pumping power and with an optical–optical conversion efficiency of 25.5%.

Pulsed solid-state laser system with fiber phase conjugation and 315 W average output power

Solid-state laser sources with high average output power and high beam quality are required for numerous applications in industry and science. To improve the beam quality, stimulated Brillouin scattering (SBS) mirrors based on optical phase conjugation are used to compensate for phase distortions in master oscillator power amplifier (MOPA) systems. SBS phase conjugation in commercially available silica optical fibers facilitates the construction of high-power solid-state laser systems with high beam quality. Here we present a flash lamp-pumped, passively Q-switched Nd:YAP system which delivers an average output power of 315 W with M2=2.6 at a wavelength of 1.08 μm.

Diffraction losses of high power solid state lasers

A uniform pumping distribution is very important in a side pumped rod geometry. Based on space-dependent rate equations, the threshold pump power and the TEM 00 mode output power of a solid state laser with a uniform pump are obtained. The diffraction losses arising from thermally induced spherical aberration have been estimated by the Strehl intensity ratio. The diffraction losses may prevent the solid state laser from ultrahigh power levels before the thermal fracture limitation. The diffraction losses for different sizes of laser beams and the laser rods are discussed. A significant increase in average power and a great decrease in thermal distortion and birefringence at cryogenic temperature have been analyzed in cooperation with thermal induced diffraction losses.

High power solid-state laser with photorefractive phase conjugate mirror

High power solid-state laser with photorefractive phase conjugate mirror

Laser-diode-pumped high-power solid-state lasers for precise material processing applications

Laser-diode-pumped high-power solid-state lasers for precise material processing applications

Czochralski growth and laser parameters of RE 3+-doped Y 2O 3 and Sc 2O 3

Yttria exhibits a thermal conductivity which is higher than that of Y 3Al 5O 12. Moreover, it can be doped with rare earth ions. The isostructural scandia has similar characteristics. Due to these properties both oxides are attractive hosts for high power solid state lasers. We have grown yttrium oxide and scandium oxide crystals from rhenium crucibles by the Czochralski technique. The size of the crystals is limited because of problems to control the crystal diameter during the growth process. However, the grown rare earth doped samples show promising spectroscopic features. We report on the spectroscopic characteristics of Y 2O 3 and Sc 2O 3 doped with Ho 3+- and Er 3+-ions. Laser operation of Er:Sc 2O 3 near 3 μm wavelength has already been demonstrated.

Self-adjusting compensating thermal lens to balance the thermally induced lens in solid-state lasers

The thermal lens is a critical issue, particularly in high-power diode-pumped solid-state laser rods. A self-adjusting scheme for compensation of the thermally induced lens is presented. The requirements for such an element and its influence on the resonator are discussed. With an appropriate compensating element and a suitable resonator design, constant beam parameters are expected to be achieved over a pump range of several kilowatts.

International forum on advanced high-power lasers and applications (AHPLA '99)

A review of reports made on the International Forum on Advanced High-Power Lasers and Applications, which was held at the beginning of November 1999 in Osaka (Japan), is presented. Five conferences were held during the forum on High-Power Laser Ablation, High-Power Lasers in Energy Engineering, High-Power Lasers in Civil Engineering and Architecture, High-Power Lasers in Manufacturing, and Advanced High-Power Lasers. The following trends in the field of high-power lasers and their applications were presented: laser fusion, laser applications in space, laser-triggered lightning, laser ablation of materials by short and ultrashort pulses, application of high-power lasers in manufacturing, application of high-power lasers in mining, laser decommissioning and decontamination of nuclear reactors, high-power solid-state and gas lasers, x-ray and free-electron lasers. One can find complete information on the forum in SPIE, vols. 3885-3889.

Rare-earth-doped sesquioxides

The sesquioxides Sc 2O 3, Y 2O 3, and Lu 2O 3 are suitable hosts for rare earth ions. Due to their high thermal conductivity they are useful for high power solid-state lasers and may be an alternative for the well-known YAG crystals. We have grown for the first time crystals in crucibles without solvents, which is a precondition for commercialization of these materials. Many lasers have been realized and show interesting properties.

Flash-Lamp-Pumped Acousto-Optic Q-switched Cr-Tm:YAG Laser

High-power Q-switched solid-state lasers operating at 2 μm wavelength are needed for many applications. Using flash-lamp pumping, we developed an acousto-optic Q-switched Cr-Tm:YAG laser and realized single transverse mode oscillation with a maximum pulse energy exceeding 0.8 J when the repetition frequency was 1 Hz. The pulse width and the corresponding peak power were 135 ns and 5.9 MW, respectively. To our knowledge, this is the highest output power of AO-Q-switched Cr-Tm:YAG lasers have ever reported.

A SOLID STATE LASER RESONATOR CAPABLE OF COMPENSATING THERMAL LENS EFFECT ADAPTIVELY

A novel resonator structure for solid state laser is proposed. A lens with short focal length is introduced in the resonator, and the laser crystal (thermal lens) is put at its focusing point, so a special lens set is composed . By using the transform circle approach it is found that the lens set functions as an optical ‘ballast’. With adjusting one end mirror along optical axis adaptively such a resonator may guarantee TEM00 mode dynamic stable operation of high-power solid state laser while thermal focal length varies within a wide range. While the beam spots of TEM00 mode at the laser crystal and end mirrors keep unchangeable.

Driver Technology for Inertial Fusion Research Introduction. Status of High Power Solid State Laser for Laser Fusion Experiments and the Prospect of Future Reactor Drivers.

The progress in development of high-power glass laser systems during the past 30 years is remarkable NIF (National Ignition Facility), which will deliver 1.8 MJ at 0.35 μm is now construction in the United States. Recently, technology that smoothes out the focal pattern has been developed to a great extent. RPP (Random Phase Plate) and PCL (Partially Coherent Laser) both gave an excellent focal pattern with standard deviation of 3% in the Gekko XII laser system. In the US, Japan and Europe, several ultra-short pulse lasers were developed for research on “fast ignition”. “Fast ignition” is a method which will reduce the total required laser energy for ignition. Because a diode-pumped, solid state laser can operate at a repetition rate of over 10 Hz with an efficiency of about 10% research area of high-power systems at the 1 kW level started to focus on the development of a driver for a commercial laser fusion reactor.

Adaptive Optics for High Power Lasers.

Adaptive optics systems for high power gas lasers and solid state lasers are reviewed. Large scale deformablemirrors with magnetostrict actuators were cooled by water for use with huge output infrared lasers. The simplemirrors which are deformable by the hydro pressure were applied to adaptive resonators for thermal lenscompensation with solid state lasers. A silicon wafer mirror was proposed as an automatic adaptive resonatorfor LD-pumped YAG lasers. New techniques employing a spatial phase modulator, phase-conjugated mirrors, and hybrid laser crystals are introduced.

High-Power and Highly-Stable Solid-State Laser for the Gravitational Wave Detector.

A high-power and highly-frequency-stabilized laser has been developed for the laser interferometric gravitational wave detector. Requirements of the light source for this are a single transverseand longitudinal mode with the power and frequency noise of 10W and 10-6Hz√Hz at 300 Hz, respectively. The frequency of a LD-pumped injection-locked Nd: YAG laser was stabilized to a high finesse Fabry-Perot optical resonator that was isolated from seismic and acoustic noise, which was achieved by controlling master laser light. We evaluated the mechanical and thermal stability of Fabry-Perot cavities of both rigid spacer type and the independently suspended mirrors type. Finally we have achieved the absolute frequency noise of2×10-2Hz/√ Hz for an injection-locked high-power laser with the output power of 9.8 W.

Measurement of temperature gradient in diode-laser-pumped high-power solid-state laser by low-coherence reflectometry

A noninvasive technique was developed to measure the temperature distribution in laser gain medium. Both axial and radial temperature distributions of a diode-laser-pumped and intracavity frequency-doubled high-power Nd:YVO4/KTP laser were characterized using a high dynamic range, low-coherence reflectometer. This measurement is important to the design of high-power solid-state lasers both in terms of mode matching and laser-rod doping selection.

High-power single-frequency tunable solid-state lasers

Experimental results are presented on the achievement of single-frequency tunable lasing in ruby, Nd-glass, and Nd:YAG lasers with electrooptic Q switching of the cavity by the injection of an external signal. An optimization of the parameters is carried out for lasers on neodymium ions in yttrium aluminum garnet, lanthanum beryllate, chromium-doped gadolinium scandium gallium garnet, and lanthanum hexaaluminate with passive Q switching of the cavity by means of lithium fluoride shutters containing F 2 − color centers. High-power single-frequency generation of giant pulses is achieved, with the output wavelength tunable over the half-width of the gain lines of the active media.