Abstract

The dynamics of pulsed line-tunable NH3 lasers are investigated by measuring small-signal gain as a function of NH3 transition, NH3 concentration, and pump intensity. Under typical experimental conditions, it is shown that the rotational populations in NH3 thermalize and that consequently the relative gain distribution can be described by a ratio of vibrational populations. Peak gains of 20% cm−1 are reported for mixtures of 4% NH3 in N2 pumped by the 9R(30) CO2 laser line. Heating that is due to increased pump absorption reduces the gain in mixtures of higher NH3 concentrations. The experimental results are in good agreement with the predictions of a rate-equation model, which can be applied to optimize line-tunable NH3 lasers.

© 1985 Optical Society of America

Full Article  |  PDF Article

References

  • View by:
  • |
  • |
  • |

  1. H. Tashiro, K. Suzuki, K. Toyoda, S. Namba, “Wide-range line-tunable oscillation of an optically pumped NH3laser,” Appl. Phys. 21, 237–240 (1980).
    [CrossRef]
  2. B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
    [CrossRef]
  3. N. Yamabayashi, T. Yoshida, K. Miyazaki, K. Fujisawa, “Infrared multi-line NH3laser and its application for pumping an InSb laser,” Opt. Commun. 30, 245–248 (1979).
    [CrossRef]
  4. N. Yamabayashi, K. Fukai, K. Miyazaki, K. Fujisawa, “Resonant pumping far-infrared NH3laser,” Appl. Phys. B 26, 33–36 (1981).
    [CrossRef]
  5. V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
    [CrossRef]
  6. H. D. Morrison, B. K. Garside, J. Reid, “Dynamics of the optically pumped midinfrared NH3laser at high pump power—Part I: inversion gain,” IEEE J. Quantum Electron. QE-20, 1051–1060 (1984).
    [CrossRef]
  7. S. M. Fry, “Optically pumped multiline NH3laser,” Opt. Commun. 19, 320–324 (1976).
    [CrossRef]
  8. C. Rolland, J. Reid, B. K. Garside, “12 μm Raman lasers in NH3pumped by low-power CO2laser pulses,” IEEE J. Quantum Electron. QE-18, 182–186 (1982).
    [CrossRef]
  9. Ortho-NH3consists of molecules with rotational quantum number K = 3n, and para-NH3consist of molecules with K = 3n±1.
  10. C. Rolland, J. Reid, B. K. Garside, “Line-tunable oscillation of a cw NH3laser from 10.7 to 13.3 μm,” Appl. Phys. Lett. 44, 380–382 (1984).
    [CrossRef]
  11. This is equivalent to setting the parameter t of Ref. 6 equal to its maximum value of t= 1.0.
  12. P. Minguzzi, M. Tonelli, A. Carrozzi, A. Di Lieto, “Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3,” J. Mol. Spectrosc. 96, 294–305 (1982).
    [CrossRef]
  13. C. H. Townes, A. L. Schawlow, Microwave Spectroscopy (Dover, New York, 1975).
  14. V. S. Letokhov, A. A. Makarov, “Kinetics of excitation of molecular vibrations by infrared laser radiation,” Sov. Phys. JETP 36, 1091–1096 (1973).
  15. For most of the pumping conditions that we examine, the relaxation rates are fast enough that the vibrational populations follow the variations in pump intensity after the peak of the pulse. As the pump absorption is saturated at intensities well below 950 kW/cm2 (see Section 4.C), changes in the intensity by as much as a factor of 2 have negligible effect on the gain calculation.
  16. To calculate temperature changes, we used heat capacities at constant volume of 29.0 J/(mol K) and 20.7 J/(mol K) for NH3and N2, respectively, derived from W. Braker, A. L. Mossman, Matheson Gas Data Book, 5th ed.(Matheson Gas Products, East Rutherford, N.J., 1971).
  17. F. E. Hovis, C. B. Moore, “Temperature dependence of vibrational energy transfer in NH3and H218O,” J. Chem.Phys. 72, 2397–2402 (1980).
    [CrossRef]
  18. Linear interpolation between rate coefficients provided by Hovis and Moore17was employed to evaluate the V–T rates up to 398 K, the maximum temperature reported. For temperatures greater than 398 K the V–T rates were maintained equal to the values for 398 K.
  19. H. D. Morrison, J. Reid, B. K. Garside, “16–21-μm linetunable NH3laser produced by two-step optical pumping,” Appl. Phys. Lett. 45, 321–323 (1984).
    [CrossRef]

1984

H. D. Morrison, B. K. Garside, J. Reid, “Dynamics of the optically pumped midinfrared NH3laser at high pump power—Part I: inversion gain,” IEEE J. Quantum Electron. QE-20, 1051–1060 (1984).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “Line-tunable oscillation of a cw NH3laser from 10.7 to 13.3 μm,” Appl. Phys. Lett. 44, 380–382 (1984).
[CrossRef]

H. D. Morrison, J. Reid, B. K. Garside, “16–21-μm linetunable NH3laser produced by two-step optical pumping,” Appl. Phys. Lett. 45, 321–323 (1984).
[CrossRef]

1983

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

1982

P. Minguzzi, M. Tonelli, A. Carrozzi, A. Di Lieto, “Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3,” J. Mol. Spectrosc. 96, 294–305 (1982).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “12 μm Raman lasers in NH3pumped by low-power CO2laser pulses,” IEEE J. Quantum Electron. QE-18, 182–186 (1982).
[CrossRef]

1981

N. Yamabayashi, K. Fukai, K. Miyazaki, K. Fujisawa, “Resonant pumping far-infrared NH3laser,” Appl. Phys. B 26, 33–36 (1981).
[CrossRef]

1980

H. Tashiro, K. Suzuki, K. Toyoda, S. Namba, “Wide-range line-tunable oscillation of an optically pumped NH3laser,” Appl. Phys. 21, 237–240 (1980).
[CrossRef]

B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
[CrossRef]

F. E. Hovis, C. B. Moore, “Temperature dependence of vibrational energy transfer in NH3and H218O,” J. Chem.Phys. 72, 2397–2402 (1980).
[CrossRef]

1979

N. Yamabayashi, T. Yoshida, K. Miyazaki, K. Fujisawa, “Infrared multi-line NH3laser and its application for pumping an InSb laser,” Opt. Commun. 30, 245–248 (1979).
[CrossRef]

1976

S. M. Fry, “Optically pumped multiline NH3laser,” Opt. Commun. 19, 320–324 (1976).
[CrossRef]

1973

V. S. Letokhov, A. A. Makarov, “Kinetics of excitation of molecular vibrations by infrared laser radiation,” Sov. Phys. JETP 36, 1091–1096 (1973).

Akhrarov, M.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

Averin, V. G.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

Baronov, G. S.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

Braker, W.

To calculate temperature changes, we used heat capacities at constant volume of 29.0 J/(mol K) and 20.7 J/(mol K) for NH3and N2, respectively, derived from W. Braker, A. L. Mossman, Matheson Gas Data Book, 5th ed.(Matheson Gas Products, East Rutherford, N.J., 1971).

Carrozzi, A.

P. Minguzzi, M. Tonelli, A. Carrozzi, A. Di Lieto, “Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3,” J. Mol. Spectrosc. 96, 294–305 (1982).
[CrossRef]

Di Lieto, A.

P. Minguzzi, M. Tonelli, A. Carrozzi, A. Di Lieto, “Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3,” J. Mol. Spectrosc. 96, 294–305 (1982).
[CrossRef]

Dyad’kin, A. P.

B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
[CrossRef]

Fry, S. M.

S. M. Fry, “Optically pumped multiline NH3laser,” Opt. Commun. 19, 320–324 (1976).
[CrossRef]

Fujisawa, K.

N. Yamabayashi, K. Fukai, K. Miyazaki, K. Fujisawa, “Resonant pumping far-infrared NH3laser,” Appl. Phys. B 26, 33–36 (1981).
[CrossRef]

N. Yamabayashi, T. Yoshida, K. Miyazaki, K. Fujisawa, “Infrared multi-line NH3laser and its application for pumping an InSb laser,” Opt. Commun. 30, 245–248 (1979).
[CrossRef]

Fukai, K.

N. Yamabayashi, K. Fukai, K. Miyazaki, K. Fujisawa, “Resonant pumping far-infrared NH3laser,” Appl. Phys. B 26, 33–36 (1981).
[CrossRef]

Garside, B. K.

H. D. Morrison, B. K. Garside, J. Reid, “Dynamics of the optically pumped midinfrared NH3laser at high pump power—Part I: inversion gain,” IEEE J. Quantum Electron. QE-20, 1051–1060 (1984).
[CrossRef]

H. D. Morrison, J. Reid, B. K. Garside, “16–21-μm linetunable NH3laser produced by two-step optical pumping,” Appl. Phys. Lett. 45, 321–323 (1984).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “Line-tunable oscillation of a cw NH3laser from 10.7 to 13.3 μm,” Appl. Phys. Lett. 44, 380–382 (1984).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “12 μm Raman lasers in NH3pumped by low-power CO2laser pulses,” IEEE J. Quantum Electron. QE-18, 182–186 (1982).
[CrossRef]

Grasyuk, A. Z.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
[CrossRef]

Hovis, F. E.

F. E. Hovis, C. B. Moore, “Temperature dependence of vibrational energy transfer in NH3and H218O,” J. Chem.Phys. 72, 2397–2402 (1980).
[CrossRef]

Letokhov, V. S.

V. S. Letokhov, A. A. Makarov, “Kinetics of excitation of molecular vibrations by infrared laser radiation,” Sov. Phys. JETP 36, 1091–1096 (1973).

Makarov, A. A.

V. S. Letokhov, A. A. Makarov, “Kinetics of excitation of molecular vibrations by infrared laser radiation,” Sov. Phys. JETP 36, 1091–1096 (1973).

Minguzzi, P.

P. Minguzzi, M. Tonelli, A. Carrozzi, A. Di Lieto, “Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3,” J. Mol. Spectrosc. 96, 294–305 (1982).
[CrossRef]

Miyazaki, K.

N. Yamabayashi, K. Fukai, K. Miyazaki, K. Fujisawa, “Resonant pumping far-infrared NH3laser,” Appl. Phys. B 26, 33–36 (1981).
[CrossRef]

N. Yamabayashi, T. Yoshida, K. Miyazaki, K. Fujisawa, “Infrared multi-line NH3laser and its application for pumping an InSb laser,” Opt. Commun. 30, 245–248 (1979).
[CrossRef]

Moore, C. B.

F. E. Hovis, C. B. Moore, “Temperature dependence of vibrational energy transfer in NH3and H218O,” J. Chem.Phys. 72, 2397–2402 (1980).
[CrossRef]

Morozov, M. G.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

Morrison, H. D.

H. D. Morrison, J. Reid, B. K. Garside, “16–21-μm linetunable NH3laser produced by two-step optical pumping,” Appl. Phys. Lett. 45, 321–323 (1984).
[CrossRef]

H. D. Morrison, B. K. Garside, J. Reid, “Dynamics of the optically pumped midinfrared NH3laser at high pump power—Part I: inversion gain,” IEEE J. Quantum Electron. QE-20, 1051–1060 (1984).
[CrossRef]

Mossman, A. L.

To calculate temperature changes, we used heat capacities at constant volume of 29.0 J/(mol K) and 20.7 J/(mol K) for NH3and N2, respectively, derived from W. Braker, A. L. Mossman, Matheson Gas Data Book, 5th ed.(Matheson Gas Products, East Rutherford, N.J., 1971).

Namba, S.

H. Tashiro, K. Suzuki, K. Toyoda, S. Namba, “Wide-range line-tunable oscillation of an optically pumped NH3laser,” Appl. Phys. 21, 237–240 (1980).
[CrossRef]

Reid, J.

H. D. Morrison, J. Reid, B. K. Garside, “16–21-μm linetunable NH3laser produced by two-step optical pumping,” Appl. Phys. Lett. 45, 321–323 (1984).
[CrossRef]

H. D. Morrison, B. K. Garside, J. Reid, “Dynamics of the optically pumped midinfrared NH3laser at high pump power—Part I: inversion gain,” IEEE J. Quantum Electron. QE-20, 1051–1060 (1984).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “Line-tunable oscillation of a cw NH3laser from 10.7 to 13.3 μm,” Appl. Phys. Lett. 44, 380–382 (1984).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “12 μm Raman lasers in NH3pumped by low-power CO2laser pulses,” IEEE J. Quantum Electron. QE-18, 182–186 (1982).
[CrossRef]

Rolland, C.

C. Rolland, J. Reid, B. K. Garside, “Line-tunable oscillation of a cw NH3laser from 10.7 to 13.3 μm,” Appl. Phys. Lett. 44, 380–382 (1984).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “12 μm Raman lasers in NH3pumped by low-power CO2laser pulses,” IEEE J. Quantum Electron. QE-18, 182–186 (1982).
[CrossRef]

Schawlow, A. L.

C. H. Townes, A. L. Schawlow, Microwave Spectroscopy (Dover, New York, 1975).

Skvortsova, E. P.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

Sukhanov, A. N.

B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
[CrossRef]

Suzuki, K.

H. Tashiro, K. Suzuki, K. Toyoda, S. Namba, “Wide-range line-tunable oscillation of an optically pumped NH3laser,” Appl. Phys. 21, 237–240 (1980).
[CrossRef]

Tashiro, H.

H. Tashiro, K. Suzuki, K. Toyoda, S. Namba, “Wide-range line-tunable oscillation of an optically pumped NH3laser,” Appl. Phys. 21, 237–240 (1980).
[CrossRef]

Tonelli, M.

P. Minguzzi, M. Tonelli, A. Carrozzi, A. Di Lieto, “Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3,” J. Mol. Spectrosc. 96, 294–305 (1982).
[CrossRef]

Townes, C. H.

C. H. Townes, A. L. Schawlow, Microwave Spectroscopy (Dover, New York, 1975).

Toyoda, K.

H. Tashiro, K. Suzuki, K. Toyoda, S. Namba, “Wide-range line-tunable oscillation of an optically pumped NH3laser,” Appl. Phys. 21, 237–240 (1980).
[CrossRef]

Vasil’ev, B. I.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
[CrossRef]

Yamabayashi, N.

N. Yamabayashi, K. Fukai, K. Miyazaki, K. Fujisawa, “Resonant pumping far-infrared NH3laser,” Appl. Phys. B 26, 33–36 (1981).
[CrossRef]

N. Yamabayashi, T. Yoshida, K. Miyazaki, K. Fujisawa, “Infrared multi-line NH3laser and its application for pumping an InSb laser,” Opt. Commun. 30, 245–248 (1979).
[CrossRef]

Yastrebkov, A. B.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
[CrossRef]

Yoshida, T.

N. Yamabayashi, T. Yoshida, K. Miyazaki, K. Fujisawa, “Infrared multi-line NH3laser and its application for pumping an InSb laser,” Opt. Commun. 30, 245–248 (1979).
[CrossRef]

Appl. Phys.

H. Tashiro, K. Suzuki, K. Toyoda, S. Namba, “Wide-range line-tunable oscillation of an optically pumped NH3laser,” Appl. Phys. 21, 237–240 (1980).
[CrossRef]

Appl. Phys. B

N. Yamabayashi, K. Fukai, K. Miyazaki, K. Fujisawa, “Resonant pumping far-infrared NH3laser,” Appl. Phys. B 26, 33–36 (1981).
[CrossRef]

Appl. Phys. Lett.

C. Rolland, J. Reid, B. K. Garside, “Line-tunable oscillation of a cw NH3laser from 10.7 to 13.3 μm,” Appl. Phys. Lett. 44, 380–382 (1984).
[CrossRef]

H. D. Morrison, J. Reid, B. K. Garside, “16–21-μm linetunable NH3laser produced by two-step optical pumping,” Appl. Phys. Lett. 45, 321–323 (1984).
[CrossRef]

IEEE J. Quantum Electron.

H. D. Morrison, B. K. Garside, J. Reid, “Dynamics of the optically pumped midinfrared NH3laser at high pump power—Part I: inversion gain,” IEEE J. Quantum Electron. QE-20, 1051–1060 (1984).
[CrossRef]

C. Rolland, J. Reid, B. K. Garside, “12 μm Raman lasers in NH3pumped by low-power CO2laser pulses,” IEEE J. Quantum Electron. QE-18, 182–186 (1982).
[CrossRef]

J. Chem.Phys.

F. E. Hovis, C. B. Moore, “Temperature dependence of vibrational energy transfer in NH3and H218O,” J. Chem.Phys. 72, 2397–2402 (1980).
[CrossRef]

J. Mol. Spectrosc.

P. Minguzzi, M. Tonelli, A. Carrozzi, A. Di Lieto, “Optoacoustic laser Stark spectroscopy in the ν2 band of 14NH3,” J. Mol. Spectrosc. 96, 294–305 (1982).
[CrossRef]

Opt. Commun.

S. M. Fry, “Optically pumped multiline NH3laser,” Opt. Commun. 19, 320–324 (1976).
[CrossRef]

N. Yamabayashi, T. Yoshida, K. Miyazaki, K. Fujisawa, “Infrared multi-line NH3laser and its application for pumping an InSb laser,” Opt. Commun. 30, 245–248 (1979).
[CrossRef]

Sov. J. Quantum Electron.

V. G. Averin, M. Akhrarov, G. S. Baronov, B. I. Vasil’ev, A. Z. Grasyuk, M. G. Morozov, E. P. Skvortsova, A. B. Yastrebkov, “Dissociation of UF6molecules involving excitation of combination modes by NH3–N2laser radiation,” Sov. J. Quantum Electron. 13, 189–194 (1983).
[CrossRef]

B. I. Vasil’ev, A. Z. Grasyuk, A. P. Dyad’kin, A. N. Sukhanov, A. B. Yastrebkov, “High-power efficient optically pumped NH3laser, tunable over the range 770–890 cm−1,” Sov. J. Quantum Electron. 10, 64–68 (1980).
[CrossRef]

Sov. Phys. JETP

V. S. Letokhov, A. A. Makarov, “Kinetics of excitation of molecular vibrations by infrared laser radiation,” Sov. Phys. JETP 36, 1091–1096 (1973).

Other

For most of the pumping conditions that we examine, the relaxation rates are fast enough that the vibrational populations follow the variations in pump intensity after the peak of the pulse. As the pump absorption is saturated at intensities well below 950 kW/cm2 (see Section 4.C), changes in the intensity by as much as a factor of 2 have negligible effect on the gain calculation.

To calculate temperature changes, we used heat capacities at constant volume of 29.0 J/(mol K) and 20.7 J/(mol K) for NH3and N2, respectively, derived from W. Braker, A. L. Mossman, Matheson Gas Data Book, 5th ed.(Matheson Gas Products, East Rutherford, N.J., 1971).

Linear interpolation between rate coefficients provided by Hovis and Moore17was employed to evaluate the V–T rates up to 398 K, the maximum temperature reported. For temperatures greater than 398 K the V–T rates were maintained equal to the values for 398 K.

C. H. Townes, A. L. Schawlow, Microwave Spectroscopy (Dover, New York, 1975).

This is equivalent to setting the parameter t of Ref. 6 equal to its maximum value of t= 1.0.

Ortho-NH3consists of molecules with rotational quantum number K = 3n, and para-NH3consist of molecules with K = 3n±1.

Cited By

OSA participates in CrossRef's Cited-By Linking service. Citing articles from OSA journals and other participating publishers are listed here.

Alert me when this article is cited.


Figures (7)

Fig. 1
Fig. 1

Schematic diagram of the experimental apparatus for measuring gain in NH3 optically pumped by the 9R(30) CO2 line. M1 and M2 transmit 60 and 90% of the R(30) pump, respectively. Both mirrors have >95% reflectivity at the wavelengths of the NH3 laser transitions.

Fig. 2
Fig. 2

Calculated small-signal gain coefficients for selected transitions as a function of the vibrational inversion parameter N1/N0, with (N0 + N1/N = 0.9. The dashed line illustrates that the gain coefficients on s transitions are significantly lower than on the corresponding a transitions.

Fig. 3
Fig. 3

Comparison between theory and experiment for small-signal gain coefficients of several NH3 transitions. The solid lines are the measured coefficients evaluated for a pump intensity of ∼130 kW/ cm2,0.6 μsec after the peak of the pump pulse. The model predicts N1/N0 = 1.40 and gives the gain coefficients indicated by the dashed lines. The estimated error for the experimental measurements is ±0.2% cm−1.

Fig. 4
Fig. 4

Comparison between theory and experiment for small-signal gain coefficients of one pair of a and s transitions as a function of pump intensity. The experimental values were measured 0.9 μsec after the peak of the pump pulse. The gas mixture is 0.87% NH3 in N2 at a total pressure of 35 Torr.

Fig. 5
Fig. 5

Experimental measurements of the small-signal gain coefficients for the aP(7, K) transitions for three different pump intensities, Ip. The values are an average of measurements made at 0.6 and 0.9 μsec after the peak of the pump pulse, and the estimated error is ±0.2% cm−1. The gas mixture is 1% NH3 in N2 at 35 Torr.

Fig. 6
Fig. 6

Comparison between theory and experiment for small-signal gain coefficients of aP(4,0) as a function of NH3 concentration in N2. The experimental points, shown with appropriate error bars, were measured for a pump intensity of ∼950 kW/cm2, 0.3 μsec after the peak of the pump pulse. The upper curve is calculated assuming that the gas temperature remains constant at 300 K. The lower curve is calculated with the gas temperature allowed to rise because of the energy absorbed from the pump.

Fig. 7
Fig. 7

Comparison between theory and experiment for small-signal gain coefficients of aP(4,0) and aQ(3,3) as a function of pump intensity. The values are an average of measurements made at 0.6 and 0.9 μsec after the peak of the pump pulse. The curves are calculated for a mixture of 0.85% NH3 in N2, and the measured pump intensities are scaled down by a factor of 0.77 (see text for details).

Metrics