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  • 1995-1999  (6)
  • 1990-1994  (31)
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  • 11
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2488-2492 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The incorporation of a retroreflecting, pseudoconjugating cone as a folding element in a double-pass unstable resonator of a high-power carbon dioxide oscillator–amplifier is presented. The concept, when implemented with a truncated cone, has yielded significant improvements in optical energy extraction efficiency, beam quality, and alignment stability. The performance of such a modified clear aperture cone resonator, in comparison with a standard roof prism cavity geometry, is discussed.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 1445-1450 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Control of frequency and amplitude of the impulses used in photoinitiated, impulse-enhanced, electrically excited laser pumping determines the E/p value of the discharge. This occurs through the influence of these impulses on the processes of electron density decay and ion-electron recombination and dissociative attachment. The degree of attachment can be controlled through the use of high-frequency excitation (f(approximately-greater-than)10 kHz), while the relative importance of ion-electron recombination increases with increasing impulse potentials. The reduced electric field E/p can thus be varied by a factor of 3, while the anode fall potential Va can be reduced from 400 to 250 V. This technique appears amenable to providing fine variation and control of the laser output power. Possible applications in materials processing are pulse shaping and rapid power modulation (superpulsing).
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 1311-1313 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Phase locking in an extended-area, multichannel, radial array, carbon dioxide laser has been investigated. Preliminary self-phase-locking percentages as high as 62% were achieved with the device. The phase-locking mechanism was determined to be the mutual optical coupling present within the central region of this geometry. As such, this region acted as a core oscillator to initiate a fundamental optical mode within each individual discharge slot.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 286-288 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A significant advancement in laser welding of heavy metal sections is presented. Operation of a photoinitiated, impulse-enhanced, electrically excited multikilowatt continuous wave (cw) laser in the pulse periodic regime results in significant improvement in weld penetration depth. High average power pulsed operation is made possible through the use of a low level trigger for a digitally controlled hydrogen thyratron pulser circuit. Peak optical powers on the order of 3 times the cw level are produced while maintaining multikilowatt average output power. A comparison of cw and pulsed welding of X70 pipeline steel is included. Burst mode welding with this system is found to yield up to a 50% increase in weld penetration with a superior weld profile when compared to cw welding at the same average power level.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 1043-1045 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A computational model is reported which is able to accurately predict discharge uniformity in large-area electrodes for transverse rf-excited CO2 lasers. The model has been employed in the development of a multi-kW radial slab array. Shunt inductors are resonated directly with the discharge impedance, thereby achieving excellent discharge uniformity while eliminating the need for frequency stabilized power sources. Experimental results suggest the model will generally be of major assistance in optimizing large-area electrodes designs, and specifically in scaling slab laser systems to multi-kW levels. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Optical and quantum electronics 24 (1992), S. S889 
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The output characteristics of several large-area multichannel unstable resonators are presented. The conventional unstable resonator and a novel toric unstable resonator, in both confocal and nonconfocal configurations, have been studied. Output beam profiles, optical energy extraction, beam focusability, resonator alignment properties and polarization states of the various resonators have been analysed in depth.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 51 (1990), S. 326-328 
    ISSN: 1432-0649
    Keywords: 42.55.Dk ; 42.60.Da ; 42.60.Kg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An on-line, electronic feedback approach for automatic alignment of a laser resonator is described. A measure of the resonator alignment error is derived by partitioning a 1% sample of the laser output into quadrants, and using standard electronic circuits to compare the average power present in each quadrant. A motorized X — Y alignment system is then used to implement the alignment changes required to maintain optimum output quality from the laser. The system is shown capable of stabilizing the output power in each quadrant of the beam to within about 2% of the optimum level.
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 1432-0649
    Keywords: 42.60.—v ; 42.80.—f ; 42.78.—b
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As advancements in laser technology result in higher-power devices, increased thermal loads experienced by resonator optical components generate instabilities in the output beam. Consequently, methods for maintaining and optimizing output-beam parameters are necessary for efficient long-term operation. This study examines a vision-based feedback control system which monitors a sampled cross-sectional image of the laser's output, and regulates both cavity mirrors, as well as the excitation level, to stabilize beam uniformity, beam steer, and output-power level. The system optimizes the output-power distribution achievable from a given laser, while significantly reducing beam steering effects. Direction of beam propagation is restricted to within 60 μrad of the desired setpoint, while the output power is stabilized to within 4%. Results clearly document a considerable improvement in laser performance through maximization of beam uniformity, minimization of beam steering, and stabilization of total output power. As such, an important degree of consistency and repeatability in output-beam parameters, essential to precision laser applications, is easily achieved. Valuable diagnostic capabilities pertaining to output beam intensity and energy profiles are also incorporated into the control system. These data may be monitored on-line or stored for subsequent analysis.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 53 (1991), S. 213-220 
    ISSN: 1432-0649
    Keywords: 52.80Mg ; 52.80Hc ; 52.50.Dg
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A plasma electrode potentially suitable for dc discharge pumped lasers has been developed based on the repetitive creation of a spark channel. The high-density plasma is a source of charge carriers for the dc discharge, thereby largely eliminating the cathode and anode falls. Potential reduction improves with increasing spark repetition frequency until about 9 kHz, at which point the falls are virtually eliminated. Fortuitously, the most beneficial regime of plasma electrode operation also appears to coincide with the optimum E/N range for CO2 laser vibrational excitation.
    Type of Medium: Electronic Resource
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  • 20
    Publication Date: 1991-02-18
    Print ISSN: 0003-6951
    Electronic ISSN: 1077-3118
    Topics: Physics
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