Abstract
We have studied RF discharges as excitation mechanisms for distributed feedback (DFB) CO2 lasers. For CO2 laser plasmas the reduced electric fieldE/N has to be in a well-defined range. The reduced electric fieldsE/N of gas discharges in the narrow gaps with widths of the order of 100 μm required for DFB are considerably above this range. In order to study the feasibility of these RF-excited discharges for DFB CO2 lasers we have measured the electron temperatureT e in their plasmas. From helium-line-intensity ratios we have deduced a lower limit of the electron temperatureT e of 4eV. The observed high intensities of bands of singly ionized nitrogen indicate an even higher electron temperature, but an efficient pumping of the upper laser level is not possible with an electron temperature above 2.5 eV.
We have estimated the electron densityn e and the current densityj e from ratios of the intesities of forbidden and allowed helium lines. The high current densityj e is in the range of abnormal glow discharges.
In the gas discharges between narrow gaps the electron oscillation amplitudex e is large than the electrode separationd. In order to replace the resulting high electron losses a high electron temperatureT e is necessary to sustain the gas discharge. Because of this high electron temperatureT e an efficient pumping of the upper laser level is not possible.
Similar content being viewed by others
References
H. Kogelnik, C.V. Shank: Appl. Phys. Lett.18, 152–154 (1971)
M. Nakamura, A. Yariv, H.W. Yen, S. Somekh, H.L. Garvin: Appl. Phys. Lett.22, 515–516 (1973)
R.O. Miles: Characteristics of a Distributed Feedback Carbon Dioxide Laser; Ph.D. Thesis, University of Utah, Salt Lake City (1978)
R.O. Miles, R.W. Grow: IEEE J. QE-17, 1071–1074 (1981)
E. Affolter, F.K. Kneubühl: Phys. Lett.74 A, 407–408 (1979)
E. Affolter, F.K. Kneubühl: IEEE J. QE-17, 1115–1122 (1981)
E.A.J. Marcatili, R.A. Schmeltzer: Bell Syst. Tech. J.43, 1783–1809 (1964)
H. Steffen, F.K. Kneubühl: IEEE J. QE-4, 992–1008 (1968)
D. Marcuse: IEEE J. QE-8, 661–669 (1972)
R.E. Collin:Field Theory of Guided Waves. McGraw-Hill, New York 1960) p. 477
B. Adam, F.K. Kneubühl: Appl. Phys.8, 281–291 (1975)
F.K. Kneubühl, E. Affolter: Infrared and Submillimeter-Waves Waveguides in Lasers, inInfrard and Millimeter Waves, Vol. 1, ed. by K.J. Button (Academic, New York 1979) pp. 235–278
J.J. Burke: Appl. Opt9, 2444–2452 (1970)
H.Nishihara, T. Inoue, I. Koyama: Appl. Phys. Lett.25, 391–393 (1974)
R.O. Miles, R.W. Grow: IEEE J. QE-14, 275–283 (1978)
J.E. Bjorkhelm, C.V. Shank: IEEE J. QE-8, 833–838 (1972)
F.K. Kneubühl, E. Affolter: Distributed Feedback Gas Lasers, inInfrared and Millimeter Waves, Vol. 5, ed. by K.J. Button (Academic, New York 1982) pp. 305–337
H.P. Preiswerk, M. Lubanski, S. Gnepf, F.K. Kneubühl: IEEE J. QE-19, 1452–1455 (1983)
H.P. Preiswerk, M. Lubanski, F.K. Kneubühl: Appl. Phys. B33, 115–131 (1984)
D. Wildmann, X. Zheng, H.P. Preiswerk, F.K. Kneubühl: Int. J. Infrared mm Waves5, 537–545 (1984)
D. Wildmann, S. Gnepf, F.K. Kneubühl: Appl. Phys. B42, 129–145 (1987)
H. Kogelnik, C.V. Shank: J. Appl. Phys.43, 2327–2335 (1972)
S. Gnepf, F.K. Kneubühl: Theory on Distributed Feedback Lasers with Weak and Strong Modulation, in Infrared and Millimeter Waves, Vol. 16, ed. by K.J. Button (Academic, New York 1984) Chap. 2
S. Gnepf, F.K. Kneubühl: Int. J. Infrared mm Waves5, 667–681 (1984)
F.K. Kneubühl: Rev. Roum. Phys. (1988) (To be published)
F.K. Kneubühl, M.W. Sigrist:Laser (Teubner, Stuttgart 1988) pp. 146–184
B.Z. Katsenelenbaum: Izv. Akad. Nauk SSSR (1961) [English transl.: FTD-ID(RS)T-0243-79, Foreign Technology Division, WP. AFB, Ohio, USA]
N.F. Kovalev, I.M. Orlova, M.I. Petelin: Sov. Phys.-Radio Phys. Quantum Electron.11, 449–450 (1968)
G.G. Denisov, M.G. Reznikov: Sov. Phys.-Radio Phys. Quantum Electron.25, 407–413 (1983)
V.L. Bratman, G.G. Denisov, N.S. Ginzburg, M.I. Peterlin: IEEE J. QE-19, 282–296 (1983)
S. Gnepf: Private communication (1988)
J. Arnesson, S. Gnepf, F.K. Kneubühl: In Proc. 1st Intl. Laser Science Conf., Dallas, TX (1985)
Zs. Bor: IEEE J. QE-16, 517–524 (1980)
Zs. Bor, A. Müller: IEEE J. QE-22, 1524–1533 (1986)
A.J. Beaulieu: Appl. Phys. Lett.16, 504–505 (1970)
W. Leuthard, W. Hermann, F.K. Kneubühl: Helv. Phys. Acta57, 259–261 (1984)
T.F. Deutsch, F.A. Horrigon, R.L. Rudko: Appl. Phys. Lett.15, 88–91 (1969)
D.L. Franzen, R.J. Collins: IEEE J. QE-6 163–164 (1970)
L.A. Newman, R.A. Hart: Laser Focus23, 80–91 (1987)
P.W. Smith: Appl. Phys. Lett.19, 132–134 (1971)
T.J. Bridges, E.G. Burkhardt, P.W. Smith: Appl. Phys. Lett.20, 403–405 (1972)
D. He, C.J. Baker, D.R. Hall: J. Appl. Phys.55, 4120–4122 (1984)
P. Vivaud, D. He, D.R. Hall: Opt. Commun.56, 185–190 (1985)
G. Francis:Ionization Phenomena in Gases (Butterworth), London 1964)
B.E. Cherrington:Gaseous Electronics and Gas Lasers (Pergamon, Oxford 1979)
F. Cap:Einführung in die Plasmaphysik (Akademie-Verlag, Berlin 1970) p. 71
E.W.B. Gill, A. von Engel: Proc. R. Soc. London, Ser. A197, 107–124 (1949)
W.L. Nighan, I.H. Bennet: Appl. Phys. Lett.14, 240–243 (1969)
A.J. Demaria: InPrinciples of Laser Plasmas ed. by G. Bekefi Wiley, New York 1976)
C.B. Moore, R.E. Wood, Be-Lok Hu, J.T. Yardley: J. Chem. Phys.46, 4222–4231 (1967)
J.C. Stephenson, R.E. Wood, C.B. Moore: J. Chem. Phys.48, 4790–4791 (1968)
W.L. Nighan: Phys. Rev. A2, 1989–2000 (1970)
J.J. Lowke, A.V. Phelps, B.W. Irwin: J. Appl. Phys.44, 4664–4671 (1973)
C.J. Baker, D.R. Hall, A.R. Davies: J. Phys. D17, 1597–1606 (1984)
G.J. Schulz: inPrinciples of Laser Plasma, ed. by G. Bekefi (Wiley, New York 1976) pp. 33–88
J.G. Xin, G. Alock, D.R. Hall: J. Phys. E19, 210–212 (1986)
D. He, D.R. Hall: IEEE J. QE-20, 209–214 (1984)
D. He, D.R. Hall: J. Appl. Phys.56, 8560857 (1984)
P. Vivaud, D.R. Hall: J. Appl. Phys.57, 1757–1758 (1985)
A. von Engel:Electric Plasma: Their Nature and Uses (Taylor and Francis, London 1983) p. 142
L. Schott: InPlasma Diagnostics, ed. by W. Lochte-Holtgreven (North-Holland, Amsterdam 1968) p. 668
G. Bekefi, C. Deutsch, B. Yaakobi: InPrinciples of Laser Plasma, ed. by G. Bekefi (Wiley, New York 1976) pp. 549–641
B. Lax, D.R. Cohn: InPrinciples of Laser Plasmas, ed. by G. Bekefi (Wiley, New York 1976) p. 543
M. Baranger, B. Mozer: Phys. Rev.123, 25–28 (1961)
C.R. Vidal: Z. Naturforsch.19a, 947–967 (1964)
R. Mewe: Br. J. Appl. Phys.18, 107–118 (1967)
H.W. Drawin: Z. Naturforsch.19a, 1451–1460 (1964)
H.R. Griem:Plasma Spectroscopy (McGraw-Hill, New York 1964) p. 160
M.N. Hirsch, E. Poss, P.N. Eisner: Phys. Rev. A1, 1615–1626 (1970)
I. Gallimberti, J.K. Hepworth, R.C. Klewe: J. Phys.7, 880–898 (1974)
P.O. Clark, M.R. Smith: Appl. Phys. Lett.9, 367–369 (1966)
M.Z. Novgrodov, A.G. Sviridov, N.N. Sobolev: IEEE J. QE-7, 508–512 (1971)
J. Polman, W.J. Witteman: IEEE J. QE-6, 154–157 (1970)
G. Bekefi, S.C. Brown: J. Appl. Phys.32, 25–30 (1961)