Abstract

Systematic investigations of signal-to-noise ratios obtained in frequency-modulation (FM) spectroscopic measurements utilizing pulsed tunable dye lasers are reported which show that the noise becomes smaller as the modulation frequency is raised relative to the laser linewidth. Thus by raising our modulation frequency and narrowing our laser linewidth, we are able to detect ~0.1% absorption in spite of ~50% shot-to-shot fluctuations in the dye laser intensity. In addition several useful aspects of FM spectroscopy using pulsed dye lasers are demonstrated. The broad tuning range, ~5 cm−1, over which continuous scans may be made is demonstrated by recording absorption spectra of I2, Br2, NO2, and Na. The sensitivity of the technique to broad absorption features is shown by absorption spectra of the above species at atmospheric pressure. The Na was in a flame showing the potential usefulness of the technique in combustion diagnostics applications. Finally the nanosecond time resolution is demonstrated by observing the absorption of a transient population in the Na 3p state which has a lifetime of 16 nsec.

© 1984 Optical Society of America

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  1. G. C. Bjorklund, Opt. Lett. 5, 15 (1980).
    [CrossRef] [PubMed]
  2. T. F. Gallagher, R. Kachru, F. Gounand, G. C. Bjorklund, W. Lenth, Opt. Lett. 7, 28 (1982).
    [CrossRef] [PubMed]
  3. N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, G. C. Bjorklund, Opt. Lett. 8, 157 (1983).
    [CrossRef] [PubMed]
  4. G. C. Bjorklund, M. D. Levenson, W. Lenth, C. Ortiz, Appl. Phys. B 32, 145 (1983).
    [CrossRef]
  5. M. G. Littman, H. J. Metcalf, Appl. Opt. 17, 2224 (1978).
    [CrossRef] [PubMed]
  6. S. Y. Wang, D. M. Bloom, D. M. Collins, Appl. Phys. Lett. 42, 190 (1983).
    [CrossRef]
  7. I. P. Kaminow, J. Liu, Proc. IEEE 51, 132 (1963).
    [CrossRef]
  8. N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, P. Pillet, H. B. van Linden van den Heuvell, to be published.
  9. R. Kachru, T. W. Mossberg, S. R. Hartmann, Phys. Rev. A 22, 1953 (1980).
    [CrossRef]
  10. J. H. Bechtel, A. R. Chraplyvy, Proc. IEEE 70, 658 (1982).
    [CrossRef]
  11. E. A. Whittaker, P. Pokrowsky, W. Zapka, K. Roche, G. C. Bjorklund, J. Quant. Spectrosc. Radiat. Transfer 30, 289 (1983).
    [CrossRef]
  12. W. Lenth, C. Ortiz, G. C. Bjorklund, Opt. Lett. 6, 351 (1981).
    [CrossRef] [PubMed]

1983 (4)

G. C. Bjorklund, M. D. Levenson, W. Lenth, C. Ortiz, Appl. Phys. B 32, 145 (1983).
[CrossRef]

S. Y. Wang, D. M. Bloom, D. M. Collins, Appl. Phys. Lett. 42, 190 (1983).
[CrossRef]

E. A. Whittaker, P. Pokrowsky, W. Zapka, K. Roche, G. C. Bjorklund, J. Quant. Spectrosc. Radiat. Transfer 30, 289 (1983).
[CrossRef]

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, G. C. Bjorklund, Opt. Lett. 8, 157 (1983).
[CrossRef] [PubMed]

1982 (2)

1981 (1)

1980 (2)

G. C. Bjorklund, Opt. Lett. 5, 15 (1980).
[CrossRef] [PubMed]

R. Kachru, T. W. Mossberg, S. R. Hartmann, Phys. Rev. A 22, 1953 (1980).
[CrossRef]

1978 (1)

1963 (1)

I. P. Kaminow, J. Liu, Proc. IEEE 51, 132 (1963).
[CrossRef]

Bechtel, J. H.

J. H. Bechtel, A. R. Chraplyvy, Proc. IEEE 70, 658 (1982).
[CrossRef]

Bjorklund, G. C.

Bloom, D. M.

S. Y. Wang, D. M. Bloom, D. M. Collins, Appl. Phys. Lett. 42, 190 (1983).
[CrossRef]

Chraplyvy, A. R.

J. H. Bechtel, A. R. Chraplyvy, Proc. IEEE 70, 658 (1982).
[CrossRef]

Collins, D. M.

S. Y. Wang, D. M. Bloom, D. M. Collins, Appl. Phys. Lett. 42, 190 (1983).
[CrossRef]

Gallagher, T. F.

Gounand, F.

Hartmann, S. R.

R. Kachru, T. W. Mossberg, S. R. Hartmann, Phys. Rev. A 22, 1953 (1980).
[CrossRef]

Kachru, R.

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, G. C. Bjorklund, Opt. Lett. 8, 157 (1983).
[CrossRef] [PubMed]

T. F. Gallagher, R. Kachru, F. Gounand, G. C. Bjorklund, W. Lenth, Opt. Lett. 7, 28 (1982).
[CrossRef] [PubMed]

R. Kachru, T. W. Mossberg, S. R. Hartmann, Phys. Rev. A 22, 1953 (1980).
[CrossRef]

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, P. Pillet, H. B. van Linden van den Heuvell, to be published.

Kaminow, I. P.

I. P. Kaminow, J. Liu, Proc. IEEE 51, 132 (1963).
[CrossRef]

Lenth, W.

Levenson, M. D.

G. C. Bjorklund, M. D. Levenson, W. Lenth, C. Ortiz, Appl. Phys. B 32, 145 (1983).
[CrossRef]

Littman, M. G.

Liu, J.

I. P. Kaminow, J. Liu, Proc. IEEE 51, 132 (1963).
[CrossRef]

Metcalf, H. J.

Mossberg, T. W.

R. Kachru, T. W. Mossberg, S. R. Hartmann, Phys. Rev. A 22, 1953 (1980).
[CrossRef]

Ortiz, C.

G. C. Bjorklund, M. D. Levenson, W. Lenth, C. Ortiz, Appl. Phys. B 32, 145 (1983).
[CrossRef]

W. Lenth, C. Ortiz, G. C. Bjorklund, Opt. Lett. 6, 351 (1981).
[CrossRef] [PubMed]

Pillet, P.

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, P. Pillet, H. B. van Linden van den Heuvell, to be published.

Pokrowsky, P.

E. A. Whittaker, P. Pokrowsky, W. Zapka, K. Roche, G. C. Bjorklund, J. Quant. Spectrosc. Radiat. Transfer 30, 289 (1983).
[CrossRef]

Roche, K.

E. A. Whittaker, P. Pokrowsky, W. Zapka, K. Roche, G. C. Bjorklund, J. Quant. Spectrosc. Radiat. Transfer 30, 289 (1983).
[CrossRef]

Tran, N. H.

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, G. C. Bjorklund, Opt. Lett. 8, 157 (1983).
[CrossRef] [PubMed]

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, P. Pillet, H. B. van Linden van den Heuvell, to be published.

van Linden van den Heuvell, H. B.

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, P. Pillet, H. B. van Linden van den Heuvell, to be published.

Wang, S. Y.

S. Y. Wang, D. M. Bloom, D. M. Collins, Appl. Phys. Lett. 42, 190 (1983).
[CrossRef]

Watjen, J. P.

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, G. C. Bjorklund, Opt. Lett. 8, 157 (1983).
[CrossRef] [PubMed]

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, P. Pillet, H. B. van Linden van den Heuvell, to be published.

Whittaker, E. A.

E. A. Whittaker, P. Pokrowsky, W. Zapka, K. Roche, G. C. Bjorklund, J. Quant. Spectrosc. Radiat. Transfer 30, 289 (1983).
[CrossRef]

Zapka, W.

E. A. Whittaker, P. Pokrowsky, W. Zapka, K. Roche, G. C. Bjorklund, J. Quant. Spectrosc. Radiat. Transfer 30, 289 (1983).
[CrossRef]

Appl. Opt. (1)

Appl. Phys. B (1)

G. C. Bjorklund, M. D. Levenson, W. Lenth, C. Ortiz, Appl. Phys. B 32, 145 (1983).
[CrossRef]

Appl. Phys. Lett. (1)

S. Y. Wang, D. M. Bloom, D. M. Collins, Appl. Phys. Lett. 42, 190 (1983).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer (1)

E. A. Whittaker, P. Pokrowsky, W. Zapka, K. Roche, G. C. Bjorklund, J. Quant. Spectrosc. Radiat. Transfer 30, 289 (1983).
[CrossRef]

Opt. Lett. (4)

Phys. Rev. A (1)

R. Kachru, T. W. Mossberg, S. R. Hartmann, Phys. Rev. A 22, 1953 (1980).
[CrossRef]

Proc. IEEE (2)

J. H. Bechtel, A. R. Chraplyvy, Proc. IEEE 70, 658 (1982).
[CrossRef]

I. P. Kaminow, J. Liu, Proc. IEEE 51, 132 (1963).
[CrossRef]

Other (1)

N. H. Tran, R. Kachru, T. F. Gallagher, J. P. Watjen, P. Pillet, H. B. van Linden van den Heuvell, to be published.

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Figures (11)

Fig. 1
Fig. 1

Experimental arrangement used to measure the signal-to-noise ratio vs modulation frequency and laser linewidth using the 12% attenuation of the retroreflection from a tunable etalon.

Fig. 2
Fig. 2

Frequency spectrum of the modulated dye laser as shown by two cycles of an 8-GHz free-spectral-range etalon. The modulation frequency is ν m = 3.51 GHz, and the dye laser has been narrowed by an external etalon to a FWHM Δν = 1.0 GHz.

Fig. 3
Fig. 3

FM signals produced by a 2-GHz wide, 12% absorption from a tunable Fabry-Perot etalon with (a) ν m = 1.56 GHz, and (b) ν m = 3.51 GHz. Two cycles of absorption from the tunable etalon are shown. The dye laser linewidth is Δν = 1.0-GHz (FWHM) in both (a) and (b).

Fig. 4
Fig. 4

Signal-to-noise vs modulation frequency and laser linewidth. See also Table I.

Fig. 5
Fig. 5

Noise-to-signal as a function of modulation frequency. The dye laser spectrum, which has a FWHM Δν = 1.0 GHz, is also shown.

Fig. 6
Fig. 6

Experimental arrangement used to observe FM absorption and dispersion produced by the Na D2 resonance line at 5890 Å.

Fig. 7
Fig. 7

(a) FM absorption, (b) FM dispersion, and (c) D-line laser-induced fluorescence signals produced by the Na D2 resonance line at 5890 Å.

Fig. 8
Fig. 8

FM absorption signals produced by (a) 10 Torr of NO2 and (b) 10 Torr of NO2 in 750 Torr of N2.

Fig. 9
Fig. 9

Simple flame apparatus used to observe FM absorption at 5890 Å by Na in a flame (not to scale).

Fig. 10
Fig. 10

(a) FM and (b) D-line laser-induced fluorescence signals produced by Na in a flame.

Fig. 11
Fig. 11

FM absorption (a) from transient Na atoms in the 3p1/2 state, showing the nanosecond time resolution of FM spectroscopy with a Nd:YAG-pumped pulsed dye laser. Laser-induced fluorescence from the 4p states is shown in (b).

Tables (1)

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Table I Signal-to-Noise in FM Spectroscopy with a Pulsed Dye Laser

Equations (1)

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E ( t ) = E 0 { cos ( 2 π ν o t ) + M 2 cos [ 2 π ( ν o + ν m ) t ] - M 2 cos [ 2 π ( ν o - ν m ) t ] } ,

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