Abstract

An interferometric device consisting of two metallic mirrors and a dielectric beam splitter of low reflectivity is used to reduce the spectral emission of a CO2 TEA laser to a single longitudinal mode (SLM). The finesse of the interferometer can be varied continuously by turning the polarization of the laser beam or in steps by using different beam splitters. The resonant reflectivity of the device was found to vary from 20 to 90% depending on transverse mode matching and alignment. With a low reflectivity beam splitter, the reliability of producing SLM pulses reached 100%. As the beam splitter reflectivity was increased, the interferometer finesse decreased resulting in a low reliability of producing SLM pulses. The maximum free spectral range which gave SLM reliably was 5 GHz. We also replaced one of the mirrors of the interferometer by a grating, and we observed SLM output on forty lines of the CO2 spectrum with a reproducibility of 80% or better. We discuss how the device could be used for intracavity pulse selection.

© 1985 Optical Society of America

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References

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  1. P. Mathieu, “Elargissement de la couverture spectrale des lasers submillimétriques haute puissance à pompage optique,” Ph.D. Thesis, Université Laval (1982).
  2. H. Walther, K. W. Rothe, Eds., Laser Spectroscopy IV (Springer-Verlag, Berlin, 1979).
  3. G. D. Holah, “Eyesafe Laser Rangefinders,” Lasers Appl.93 (Sept.1984).
  4. A. Girard, “The Effects of the Insertion of a CW, Low-Pressure CO2 Laser into a TEA CO2 Laser Cavity,” Opt. Commun. 11, 346 (1974).
    [CrossRef]
  5. A. Gondhalekar et al., “Single Longitudinal Mode Operation of High Pressure Pulsed CO2 Lasers,” Phys. Lett. A 46, 229 (1973).
    [CrossRef]
  6. P. W. Smith, “Mode Selection in Lasers,” Proc. IEEE 60, 422 (1972).
    [CrossRef]
  7. W. W. Rigrod, “Selectivity of Open-Ended Interferometric Resonators,” IEEE J. Quantum Electron. QE-6, 9 (1970).
    [CrossRef]
  8. P. Bernard et al., “Fine Frequency Tuning of High Power TEA-CO2 Lasers,” Opt. Commun. 37, 285 (1981) and reference listed within.
    [CrossRef]
  9. V. Y. Petrunkin et al., “Longitudinal Mode Selection in a He–Ne Laser with a Four-Mirror T-Shaped Resonator,” Sov. Phys. Tech. Phys. 13, 1591 (1969).
  10. R. Damaschini, “Sélecteur de fréquences pour laser à gaz,” C. R. Acad. Sci. Ser. B 268, 1169 (1969).
  11. G. Giuliani et al., “Multipass-Prism Interferometer for Fine-Frequency Tuning, Single Mode Operation of TEA-CO2 Lasers,” Opt. Lett. 9, 393 (1984).
    [CrossRef] [PubMed]
  12. E. Yablonovich, “Spectral Broadening in the Light Transmitted through a Rapidly Growing Plasma,” Phys. Rev. Lett. 31, 877 (1973).
    [CrossRef]
  13. R. A. Fisher, B. J. Feldman, “Generation of Single Ultrashort CO2 Laser Pulses in a Fabry-Perot Interferometer,” Opt. Lett. 1, 161 (1977).
    [CrossRef] [PubMed]
  14. H. Kogelnik, T. Li, “Laser Beams and Resonators,” Proc. IEEE 54, 1312 (1966).
    [CrossRef]
  15. W. R. Leeb, “Losses Introduced by Tilting Intracavity Etalons,” Appl. Phys. 6, 267 (1975).
    [CrossRef]
  16. K. Kinosita, “Numerical Evaluation of the Intensity Curve of a Multiple-Beam Fizeau Fringe,” J. Phys. Soc. Jpn. 8, 219 (1953).
    [CrossRef]
  17. M. Piche, P. A. Belanger, “Short Pulse Generation from Intracavity Laser Breakdown Plasmas,” Opt. Commun. 24, 158 (1978).
    [CrossRef]

1984

1981

P. Bernard et al., “Fine Frequency Tuning of High Power TEA-CO2 Lasers,” Opt. Commun. 37, 285 (1981) and reference listed within.
[CrossRef]

1978

M. Piche, P. A. Belanger, “Short Pulse Generation from Intracavity Laser Breakdown Plasmas,” Opt. Commun. 24, 158 (1978).
[CrossRef]

1977

1975

W. R. Leeb, “Losses Introduced by Tilting Intracavity Etalons,” Appl. Phys. 6, 267 (1975).
[CrossRef]

1974

A. Girard, “The Effects of the Insertion of a CW, Low-Pressure CO2 Laser into a TEA CO2 Laser Cavity,” Opt. Commun. 11, 346 (1974).
[CrossRef]

1973

A. Gondhalekar et al., “Single Longitudinal Mode Operation of High Pressure Pulsed CO2 Lasers,” Phys. Lett. A 46, 229 (1973).
[CrossRef]

E. Yablonovich, “Spectral Broadening in the Light Transmitted through a Rapidly Growing Plasma,” Phys. Rev. Lett. 31, 877 (1973).
[CrossRef]

1972

P. W. Smith, “Mode Selection in Lasers,” Proc. IEEE 60, 422 (1972).
[CrossRef]

1970

W. W. Rigrod, “Selectivity of Open-Ended Interferometric Resonators,” IEEE J. Quantum Electron. QE-6, 9 (1970).
[CrossRef]

1969

V. Y. Petrunkin et al., “Longitudinal Mode Selection in a He–Ne Laser with a Four-Mirror T-Shaped Resonator,” Sov. Phys. Tech. Phys. 13, 1591 (1969).

R. Damaschini, “Sélecteur de fréquences pour laser à gaz,” C. R. Acad. Sci. Ser. B 268, 1169 (1969).

1966

H. Kogelnik, T. Li, “Laser Beams and Resonators,” Proc. IEEE 54, 1312 (1966).
[CrossRef]

1953

K. Kinosita, “Numerical Evaluation of the Intensity Curve of a Multiple-Beam Fizeau Fringe,” J. Phys. Soc. Jpn. 8, 219 (1953).
[CrossRef]

Belanger, P. A.

M. Piche, P. A. Belanger, “Short Pulse Generation from Intracavity Laser Breakdown Plasmas,” Opt. Commun. 24, 158 (1978).
[CrossRef]

Bernard, P.

P. Bernard et al., “Fine Frequency Tuning of High Power TEA-CO2 Lasers,” Opt. Commun. 37, 285 (1981) and reference listed within.
[CrossRef]

Damaschini, R.

R. Damaschini, “Sélecteur de fréquences pour laser à gaz,” C. R. Acad. Sci. Ser. B 268, 1169 (1969).

Feldman, B. J.

Fisher, R. A.

Girard, A.

A. Girard, “The Effects of the Insertion of a CW, Low-Pressure CO2 Laser into a TEA CO2 Laser Cavity,” Opt. Commun. 11, 346 (1974).
[CrossRef]

Giuliani, G.

Gondhalekar, A.

A. Gondhalekar et al., “Single Longitudinal Mode Operation of High Pressure Pulsed CO2 Lasers,” Phys. Lett. A 46, 229 (1973).
[CrossRef]

Holah, G. D.

G. D. Holah, “Eyesafe Laser Rangefinders,” Lasers Appl.93 (Sept.1984).

Kinosita, K.

K. Kinosita, “Numerical Evaluation of the Intensity Curve of a Multiple-Beam Fizeau Fringe,” J. Phys. Soc. Jpn. 8, 219 (1953).
[CrossRef]

Kogelnik, H.

H. Kogelnik, T. Li, “Laser Beams and Resonators,” Proc. IEEE 54, 1312 (1966).
[CrossRef]

Leeb, W. R.

W. R. Leeb, “Losses Introduced by Tilting Intracavity Etalons,” Appl. Phys. 6, 267 (1975).
[CrossRef]

Li, T.

H. Kogelnik, T. Li, “Laser Beams and Resonators,” Proc. IEEE 54, 1312 (1966).
[CrossRef]

Mathieu, P.

P. Mathieu, “Elargissement de la couverture spectrale des lasers submillimétriques haute puissance à pompage optique,” Ph.D. Thesis, Université Laval (1982).

Petrunkin, V. Y.

V. Y. Petrunkin et al., “Longitudinal Mode Selection in a He–Ne Laser with a Four-Mirror T-Shaped Resonator,” Sov. Phys. Tech. Phys. 13, 1591 (1969).

Piche, M.

M. Piche, P. A. Belanger, “Short Pulse Generation from Intracavity Laser Breakdown Plasmas,” Opt. Commun. 24, 158 (1978).
[CrossRef]

Rigrod, W. W.

W. W. Rigrod, “Selectivity of Open-Ended Interferometric Resonators,” IEEE J. Quantum Electron. QE-6, 9 (1970).
[CrossRef]

Smith, P. W.

P. W. Smith, “Mode Selection in Lasers,” Proc. IEEE 60, 422 (1972).
[CrossRef]

Yablonovich, E.

E. Yablonovich, “Spectral Broadening in the Light Transmitted through a Rapidly Growing Plasma,” Phys. Rev. Lett. 31, 877 (1973).
[CrossRef]

Appl. Phys.

W. R. Leeb, “Losses Introduced by Tilting Intracavity Etalons,” Appl. Phys. 6, 267 (1975).
[CrossRef]

C. R. Acad. Sci. Ser. B

R. Damaschini, “Sélecteur de fréquences pour laser à gaz,” C. R. Acad. Sci. Ser. B 268, 1169 (1969).

IEEE J. Quantum Electron.

W. W. Rigrod, “Selectivity of Open-Ended Interferometric Resonators,” IEEE J. Quantum Electron. QE-6, 9 (1970).
[CrossRef]

J. Phys. Soc. Jpn.

K. Kinosita, “Numerical Evaluation of the Intensity Curve of a Multiple-Beam Fizeau Fringe,” J. Phys. Soc. Jpn. 8, 219 (1953).
[CrossRef]

Lasers Appl.

G. D. Holah, “Eyesafe Laser Rangefinders,” Lasers Appl.93 (Sept.1984).

Opt. Commun.

A. Girard, “The Effects of the Insertion of a CW, Low-Pressure CO2 Laser into a TEA CO2 Laser Cavity,” Opt. Commun. 11, 346 (1974).
[CrossRef]

P. Bernard et al., “Fine Frequency Tuning of High Power TEA-CO2 Lasers,” Opt. Commun. 37, 285 (1981) and reference listed within.
[CrossRef]

M. Piche, P. A. Belanger, “Short Pulse Generation from Intracavity Laser Breakdown Plasmas,” Opt. Commun. 24, 158 (1978).
[CrossRef]

Opt. Lett.

Phys. Lett. A

A. Gondhalekar et al., “Single Longitudinal Mode Operation of High Pressure Pulsed CO2 Lasers,” Phys. Lett. A 46, 229 (1973).
[CrossRef]

Phys. Rev. Lett.

E. Yablonovich, “Spectral Broadening in the Light Transmitted through a Rapidly Growing Plasma,” Phys. Rev. Lett. 31, 877 (1973).
[CrossRef]

Proc. IEEE

H. Kogelnik, T. Li, “Laser Beams and Resonators,” Proc. IEEE 54, 1312 (1966).
[CrossRef]

P. W. Smith, “Mode Selection in Lasers,” Proc. IEEE 60, 422 (1972).
[CrossRef]

Sov. Phys. Tech. Phys.

V. Y. Petrunkin et al., “Longitudinal Mode Selection in a He–Ne Laser with a Four-Mirror T-Shaped Resonator,” Sov. Phys. Tech. Phys. 13, 1591 (1969).

Other

P. Mathieu, “Elargissement de la couverture spectrale des lasers submillimétriques haute puissance à pompage optique,” Ph.D. Thesis, Université Laval (1982).

H. Walther, K. W. Rothe, Eds., Laser Spectroscopy IV (Springer-Verlag, Berlin, 1979).

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Figures (5)

Fig. 1
Fig. 1

Gain on the CO2P20 line at 10.6 μm showing (a) longitudinal resonator modes separated by c/2L and (b) the effect of an interferometer with a free spectral range given by c/2l in the laser cavity.

Fig. 2
Fig. 2

Experimental setup: (a) modified Fabry-Perot interferometer consisting of two highly reflecting mirrors and a beam splitter; (b) MFP with a grating; (c) a beam expander used to increase the resonant reflectivity of the interferometer.

Fig. 3
Fig. 3

Two modes separated by Δ = c/2l. Dashed line: mirror and grating are aligned at this frequency, and the resonant reflectivity is 100%. Solid line: slight misalignment is caused by the grating at this frequency: (a) R0 = 30%; l ≈ 6 cm; (b) R0 = 20%; l ≈ 2.4 cm.

Fig. 4
Fig. 4

Output showing (a) SLM operation, (b) high frequency beating, (c) low frequency beating.

Fig. 5
Fig. 5

Reflectivity of the MFP: the apparent difference in the widths is due to a nonlinearity of the electromechanical translator.

Tables (1)

Tables Icon

Table I Occurrences of HF Beating, LF Beating, and SLM (in Percent) based on 100–150 Shots

Equations (16)

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R ( υ ) = R 1 ( 1 T 0 1 T 0 R 1 R 2 ) 2 1 1 + F sin 2 ( 2 π υ l c ) ,
F = 4 T 0 R 1 R 2 ( 1 T 0 R 1 R 2 ) 2 .
F π F 2 = π T 0 R 1 R 2 1 T 0 R 1 R 2 .
γ e f f c l n 2 π l n F ,
( π w 01 2 λ ) 2 = L 2 G 1 G 2 ( 1 G 1 G 2 ) ( G 1 + G 2 2 G 1 G 2 ) 2 ,
( π w 02 2 λ ) 2 = l 2 4 ( 1 + g ) ( 1 g ) .
L 2 G 1 G 2 ( 1 G 1 G 2 ) ( G 1 + G 2 2 G 1 G 2 ) 2 = l 2 4 ( 1 + g ) ( 1 g ) .
L 1 = L G 2 ( 1 G 1 ) G 1 + G 2 2 G 1 G 2 .
g = G 1 G 2 + 2 G 1 G 2 2 G 2 G 1 2 G 1 + G 2 2 G 1 G 2 .
R 1 = ( 2 L l 1 ) R 3 ( 2 L l 2 ) L .
R ( υ ) = | R 0 R 1 n = 0 ( T 0 R 1 R 2 ) n exp ( i δ n ) | 2 ,
δ n 4 π n l υ c ( 1 2 n 2 + 1 3 Δ θ 2 ) .
λ = 2 a sin θ ,
Δ λ 2 a cos θ Δ θ .
Δ θ = λ 0 2 / ( 4 a l cos θ ) .
δ n 4 π n l υ c [ 1 1 l 2 2 n 2 + 1 3 ( λ 0 2 4 a cos θ ) 2 ] ,

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