Applied Physics B

, Volume 26, Issue 3, pp 203–210 | Cite as

Second-harmonic detection with tunable diode lasers — Comparison of experiment and theory

  • J. Reid
  • D. Labrie
Contributed Papers

Abstract

A series of experiments are carried out by current modulating a tunable diode laser, and slowly ramping the wavelength to scan weak absorption lines in gases at pressures ranging from 2 to 60 Torr. A lock-in amplifier detects the second harmonic (2f) of the modulation frequency, and the experimental 2f signals are compared with theory. Detailed measurements are made on Lorentzian, Voigt, and Gaussian line profiles, over a wide range of modulation amplitudes. Excellent agreement between experiment and calculation is obtained in all cases. This quantitative understanding enables one to derive true lineshapes and linewidths of very weak absorption lines from measurements of 2f lineshapes only. Results are applicable to trace gas detection using tunable diode lasers, and to other areas of spectroscopy and magnetic resonance where harmonic detection techniques are routinely employed to monitor weak signals.

PACS

07.65 42.80 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    J.Reid, J.Shewchun, B.K.Garside, E.A.Ballik: Appl. Opt.17, 300–307 (1978)Google Scholar
  2. 2.
    J.Reid, B.K.Garside, J.Shewchun, M.El-Sherbiny, E.A.Ballik: Appl. Opt.17, 1806–1810 (1978)Google Scholar
  3. 3.
    J.Reid, M.El-Sherbiny, B.K.Garside, E.A.Ballik: Appl. Opt.19, 3349–3354 (1980)Google Scholar
  4. 4.
    H.Wahlquist: J. Chem. Phys.35, 1708–1710 (1961)Google Scholar
  5. 5.
    R.Arndt: J. Appl. Phys.36, 2522–2524 (1965)Google Scholar
  6. 6.
    G.V.H.Wilson: J. Appl. Phys.34, 3276–3285 (1963)Google Scholar
  7. 7.
    M.L.Olson, D.L.Grieble, P.R.Griffiths: Appl. Spectrosc.34, 50–56 (1980);34, 56–60 (1980)Google Scholar
  8. 8.
    E.D.Hinkley, R.T.Ku, P.L.Kelly: InLaser Monitoring of the Atmosphere, ed. by E.D. Hinkley, Topics Appl. Phys.14 (Springer, Berlin, Heidelberg, New York 1976) p. 237Google Scholar
  9. 9.
    The theory given in Sect. 1 is still a good approximation whenI 0(ν) has a small linear variation with ν [7]Google Scholar
  10. 10.
    For convenience, we use —H 2(χ,m) to illustrate theory and experiment. This ensures that at line centre the signal is positiveGoogle Scholar
  11. 11.
    V.N.Faddeyeva, N.M.Terent'ev: In tables of values of the function\(w(z) = \exp ( - z^2 )\left[ {1 + \frac{{2i}}{{\sqrt \pi }}\int\limits_0^z {\exp (t^2 )dt} } \right]\) for complex argument (Pergamon Press, London 1961)Google Scholar
  12. 12.
    J.Humlicek: J. Quant. Spectrosc. Radiat. Transfer21, 309–313 (1978)Google Scholar
  13. 13.
    L.S.Rothman, S.A.Clough, R.A.McClatchey, L.G.Young, D.E.Snider, A.Goldman: Appl. Opt.17, 507 (1978)Google Scholar
  14. 14.
    R.C.Isler: J.Opt. Soc. Am.59, 727–733 (1969)Google Scholar
  15. 15.
    We convert the modulation voltageA to current modulation by using the manufacturer's specifications. m is converted to cm−1 using the known SO2 linewidth [13]Google Scholar
  16. 16.
    R.S.Eng, A.W.Mantz, T.R.Todd: Appl. Opt.18, 1088–1091 (1979)Google Scholar
  17. 17.
    D.Labrie, J.Reid: Appl. Phys.24, 381–386 (1981)Google Scholar

Copyright information

© Springer-Verlag 1981

Authors and Affiliations

  • J. Reid
    • 1
  • D. Labrie
    • 1
  1. 1.Departments of Engineering Physics and PhysicsMcMaster UniversityHamiltonCanada

Personalised recommendations