The CO2 Laser

Witteman, W.J.

doi:10.1007/978-3-540-47744-0

Cited by 174 publications

(110 citation statements)

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“…As the energy deposition increases, the sheath with the positive charge becomes stronger. This agrees with qualitative models [10,12] and a theoretical prediction [11].…”

Section: The Voltage-current Characteristicssupporting

confidence: 90%

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Influence of the electric field frequency on the performance of a RF excited CO 2 waveguide laser

Ochkin¹,

Witteman²,

Ilukhin³

et al. 1996

Applied Physics B: Lasers and Optics

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Abstract. An analysis is presented of the effect of the RF frequency on the active media of CO2 waveguide lasers. It is found that the characteristics are improved with increasing RF frequency because the space charge sheath width decreases with increasing excitation frequency. We also found that the sheath width decreases with the discharge current; this fact was never discussed before. The higher the exciting frequency the higher is the maximum input power of the discharge in the stable low current mode. It is attractive to extend the input power while keeping the discharge in this mode. Finally, a stabilizing excitation technique is described for the inherent unstable region of the discharge.It is well known that the best performance of CO 2 waveguide lasers is obtained with RF excitation [1][2][3][4][5][6]. The choice of the used excitation frequency was mainly determined by practical arguments like the available power supplies. Its impact on the laser performance has not been studied thoroughly. So far this problem received little attention. There are two main points of view. There is the opinion that a change of frequency influences only the properties of the quasi-neutral plasma of the active medium [-2,7]. The other one is that the frequency changes the thickness of the charge sheaths near the electrodes so that the energy deposition into the quasineutral plasma and consequently the laser output are influenced [8,9]. The theoretical background for these considerations was discussed either phenomenologically or qualitatively.In a previous paper we presented the laser characteristics of the CO2 waveguide system with RF discharge [5]. The present paper, based on the previous model, will analyse the mechanism of laser excitation as it depends on various parameters, especially on the RF field frequency. Initial assumptions and system descriptionThe system that will be analysed theoretically is our experimental device [4,5] having a waveguide discharge volume of 2.25 × 2.25 x 370 mm 3. The used gas mixture is CO2-Nz-He (1:1:8) at a pressure of 100 Tort. The RF voltage is by means of parallel shunt inductors homogeneously applied to the two parallel electrodes. The field distribution in the discharge is calculated by solving the Poisson equation with the appropriate boundary conditions determined by the oscillating voltage over the electrodes. Because of the homogeneity of the RF discharge the problem is treated one-dimensionally with the coordinate x perpendicular to the electrode surfaces. The Boltzmann equation for the electron energy distribution is then solved by using the relevant cross-sections for the electronic excitations, vibrational excitations, dissociation of the CO2 molecule and the ionisations of N2 and CO2. The discharge heat is removed through both electrodes and through the ceramic side walls of the cavity. The considered frequencies of the electric field are in the range from 62 to 233 MHz. The relaxation frequency of the electron drift velocity is assumed to be larger than the frequency of ...

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“…As the energy deposition increases, the sheath with the positive charge becomes stronger. This agrees with qualitative models [10,12] and a theoretical prediction [11].…”

Section: The Voltage-current Characteristicssupporting

confidence: 90%

“…Circuit stability can then be obtained by inserting a ballast resistor in series. This introduces additional power losses and lowers the efficiency [1,11]. An additional advantage of the RF discharge is the absence of a ballast resistor.…”

Section: Discharge Characteristics and The Stability Regimementioning

confidence: 99%

Influence of the electric field frequency on the performance of a RF excited CO 2 waveguide laser

Ochkin¹,

Witteman²,

Ilukhin³

et al. 1996

Applied Physics B: Lasers and Optics

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“…CO2 lasers can operate with 15 to 20% efficiency with 50 kilowatt average power for CW discharges and nearly 1 MW for gas-dynamic lasers [29]. For long pulses, they can operate at 1 kHz with several kW average power.…”

Section: Tw Laser Technologies Needing Major Developmentmentioning

confidence: 99%

Summary report: Working group 7 on “laser sources for particle acceleration”

Downer¹,

Siders²

1997

The Seventh Workshop on Advanced Accelerator Concepts

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“…The transmittance of both mirrors at the 350-rim wavelength of the competing XeF(B-X) transition was higher than 85 ~. Because the experimental conditions and the pumping source intensity were well defined, this comparison was used to determine the coefficient ~ of proportionality between the refractive index variation and the initial density of XeF2 in relation (13). The experimentally measured laser energy was 225 m J, while the calculation performed at r = 2.9.10 -7 cm 3 yielded 220 mJ.…”

Section: Xef(c-a) Laser With 5-kj Input Energymentioning

confidence: 99%

“…Since experiments with small-scale lasers were used to determine the coeaicient e in (13), which is the only fitting parameter in the numerical code, we had to compare our computation results with the experimental data of other authors. It was desirable that their experimental conditions be different from ours.…”

Section: Xef(c-a) Laser With 90-kj Input Energymentioning

confidence: 99%

State of and prospects for XeF(C−A) optically pumped lasers

et al. 1997

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Experimental and theoretical results are presented on an XeF(C-A) blue-green laser driven by 5-kJ energy. The laser was pumped by a ferrite-induced discharge of 90 cm in length. The output energy of 0.22 J was obtained with a plane-parallel resonator. A program to simulate laser operation has been developed. Numerical results for a wide range of conditions are compared with experiments performed by us and by other authors. It is found that intracavity refractive losses limit laser operation for XeF pressures above 3 torr. The laser efficiency strongly depends on the discharge-to-cavity length ratio. Possible ways to increase the laser power and efficiency are discussed.

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The CO2 Laser

Cited by 174 publications

References 0 publications

Influence of the electric field frequency on the performance of a RF excited CO 2 waveguide laser

Influence of the electric field frequency on the performance of a RF excited CO 2 waveguide laser

Summary report: Working group 7 on “laser sources for particle acceleration”

State of and prospects for XeF(C−A) optically pumped lasers

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