Abstract

A new technique has been developed to enhance the detection of absorption spectra of weak absorbers. Preliminary experiments, which illustrate the technique, are described. An organic-dye laser normally emits a continuous spectrum with a bandwidth of 2–10 nm. The effect of placing an absorbing-gas sample inside a dye-laser cavity results in laser quenching at those wavelengths where the sample absorption exceeds a minimum threshold absorption. The threshold for absorption quenching appears to be very low; absorption of the order of 0.5% can cause spoiling of laser action at the absorbing wavelengths and displacement of laser emission to wavelengths where absorption is below the critical switching level. Detection limits for atoms and molecules by means of absorption spectroscopy inside a laser cavity can be more than two orders of magnitude lower than those attainable through conventional absorption spectroscopy. Experiments with I<sub>2</sub> and sodium both inside and outside the cavity of a rhodamine 6-G laser are described. A qualitative consideration of the proposed mechanism indicates that the technique can be significantly improved with further development.

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  1. B. H. Soffer and B. B. McFarland, Appl. Phys. Letters 10, 266 (1967).
  2. P. P. Sorokin, J. R. Lankard, V. L. Moruzzi, and E. C. Hammond, J. Chem. 48, 4726 (1968).
  3. D. J. Bradley, A. J. F. Durrant, G. M. Gale, M. Moore, and P. D. Smith, IEEE J. QE-4, 707 (1968).
  4. H. Furumoto and H. Ceccon, AppL. Phys. Letters 13, 335 (1968).
  5. The absorption cell had quartz windows, perpendicular to the laser beam, which were not antireflection coated.
  6. A. M. Bass and K. G. Kessler, J. Opt. Soc. Am. 49, 1223 (1959).
  7. A. R. Gordon, J. Chem. Phys. 4, 100 (1936).
  8. This spectrum was taken on a photoelectric recording spectrophotometer because the film spectrogram would not reproduce well enough for publication.
  9. G. P. Baxter, C. H. Hickey, and W. C. Holms, J. Am. Chem. Soc. 29, 127 (1907).
  10. G. P. Baxter and M. R. Grosse, J. Am. Chem. Soc. 37, 1061 (1915).
  11. Under ideal steady-state or pseudo-steady-state conditions, the excited-state population of an operating laser is held at threshold for wavelengths of minimum cavity loss. At wavelengths where increased absorption occurs, the population of the excited state is below threshold and no laser emission at these wavelengths could occur. However, with pulsed excitation, the excited-state concentration temporarily exceeds threshold, and laser emission can occur at wavelengths where absorption losses are higher.For a cw laser, transient fluctuations in other cavity losses also lead to similar fluctuations in excited-state concentrations. The parameter, δ, reflects the level of absorption losses which can inhibit laser action in the presence of these fluctuations.

Bass, A. M.

A. M. Bass and K. G. Kessler, J. Opt. Soc. Am. 49, 1223 (1959).

Baxter, G. P.

G. P. Baxter and M. R. Grosse, J. Am. Chem. Soc. 37, 1061 (1915).

G. P. Baxter, C. H. Hickey, and W. C. Holms, J. Am. Chem. Soc. 29, 127 (1907).

Bradley, D. J.

D. J. Bradley, A. J. F. Durrant, G. M. Gale, M. Moore, and P. D. Smith, IEEE J. QE-4, 707 (1968).

Ceccon, H.

H. Furumoto and H. Ceccon, AppL. Phys. Letters 13, 335 (1968).

Durrant, A. J. F.

D. J. Bradley, A. J. F. Durrant, G. M. Gale, M. Moore, and P. D. Smith, IEEE J. QE-4, 707 (1968).

Furumoto, H.

H. Furumoto and H. Ceccon, AppL. Phys. Letters 13, 335 (1968).

Gale, G. M.

D. J. Bradley, A. J. F. Durrant, G. M. Gale, M. Moore, and P. D. Smith, IEEE J. QE-4, 707 (1968).

Gordon, A. R.

A. R. Gordon, J. Chem. Phys. 4, 100 (1936).

Grosse, M. R.

G. P. Baxter and M. R. Grosse, J. Am. Chem. Soc. 37, 1061 (1915).

Hammond, E. C.

P. P. Sorokin, J. R. Lankard, V. L. Moruzzi, and E. C. Hammond, J. Chem. 48, 4726 (1968).

Hickey, C. H.

G. P. Baxter, C. H. Hickey, and W. C. Holms, J. Am. Chem. Soc. 29, 127 (1907).

Holms, W. C.

G. P. Baxter, C. H. Hickey, and W. C. Holms, J. Am. Chem. Soc. 29, 127 (1907).

Kessler, K. G.

A. M. Bass and K. G. Kessler, J. Opt. Soc. Am. 49, 1223 (1959).

Lankard, J. R.

P. P. Sorokin, J. R. Lankard, V. L. Moruzzi, and E. C. Hammond, J. Chem. 48, 4726 (1968).

McFarland, B. B.

B. H. Soffer and B. B. McFarland, Appl. Phys. Letters 10, 266 (1967).

Moore, M.

D. J. Bradley, A. J. F. Durrant, G. M. Gale, M. Moore, and P. D. Smith, IEEE J. QE-4, 707 (1968).

Moruzzi, V. L.

P. P. Sorokin, J. R. Lankard, V. L. Moruzzi, and E. C. Hammond, J. Chem. 48, 4726 (1968).

Smith, P. D.

D. J. Bradley, A. J. F. Durrant, G. M. Gale, M. Moore, and P. D. Smith, IEEE J. QE-4, 707 (1968).

Soffer, B. H.

B. H. Soffer and B. B. McFarland, Appl. Phys. Letters 10, 266 (1967).

Sorokin, P. P.

P. P. Sorokin, J. R. Lankard, V. L. Moruzzi, and E. C. Hammond, J. Chem. 48, 4726 (1968).

Other (11)

B. H. Soffer and B. B. McFarland, Appl. Phys. Letters 10, 266 (1967).

P. P. Sorokin, J. R. Lankard, V. L. Moruzzi, and E. C. Hammond, J. Chem. 48, 4726 (1968).

D. J. Bradley, A. J. F. Durrant, G. M. Gale, M. Moore, and P. D. Smith, IEEE J. QE-4, 707 (1968).

H. Furumoto and H. Ceccon, AppL. Phys. Letters 13, 335 (1968).

The absorption cell had quartz windows, perpendicular to the laser beam, which were not antireflection coated.

A. M. Bass and K. G. Kessler, J. Opt. Soc. Am. 49, 1223 (1959).

A. R. Gordon, J. Chem. Phys. 4, 100 (1936).

This spectrum was taken on a photoelectric recording spectrophotometer because the film spectrogram would not reproduce well enough for publication.

G. P. Baxter, C. H. Hickey, and W. C. Holms, J. Am. Chem. Soc. 29, 127 (1907).

G. P. Baxter and M. R. Grosse, J. Am. Chem. Soc. 37, 1061 (1915).

Under ideal steady-state or pseudo-steady-state conditions, the excited-state population of an operating laser is held at threshold for wavelengths of minimum cavity loss. At wavelengths where increased absorption occurs, the population of the excited state is below threshold and no laser emission at these wavelengths could occur. However, with pulsed excitation, the excited-state concentration temporarily exceeds threshold, and laser emission can occur at wavelengths where absorption losses are higher.For a cw laser, transient fluctuations in other cavity losses also lead to similar fluctuations in excited-state concentrations. The parameter, δ, reflects the level of absorption losses which can inhibit laser action in the presence of these fluctuations.

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