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Journal of the Optical Society of America B

Journal of the Optical Society of America B

| OPTICAL PHYSICS

  • Vol. 2, Iss. 4 — Apr. 1, 1985
  • pp: 535–540

Gain dynamics in pulsed 12-μm NH3 lasers

H. D. Morrison, B. K. Garside, and J. Reid  »View Author Affiliations


JOSA B, Vol. 2, Issue 4, pp. 535-540 (1985)
http://dx.doi.org/10.1364/JOSAB.2.000535


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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

History
Original Manuscript: August 6, 1984
Manuscript Accepted: November 19, 1984
Published: April 1, 1985

Citation
H. D. Morrison, B. K. Garside, and J. Reid, "Gain dynamics in pulsed 12-μm NH3 lasers," J. Opt. Soc. Am. B 2, 535-540 (1985)
http://www.opticsinfobase.org/josab/abstract.cfm?URI=josab-2-4-535


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References

  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]

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