Abstract

Simultaneous and independent lasing on two different atomic lines is achieved with spatial resolution of laser eigenstates in conjunction with intracavity frequency selection. A sensitivity of 0.3 part in 106 meter in the differential detection of methane in 1 atm of air is experimentally demonstrated with this novel dual-wavelength laser. Monitoring the output intensities of the two orthogonally polarized eigenstates permits absolute measurement of methane concentration.

© 1994 Optical Society of America

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References

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  1. G. J. Whiting, J. P. Chanton, “Primary production control of methane emission from wetlands,” Nature (London) 364, 794–795 (1993).
    [Crossref]
  2. W. B. Grant, “He–Ne and cw CO2 laser long-path systems for gas detection,” Appl. Opt. 25, 709–719 (1986).
    [Crossref] [PubMed]
  3. R. M. Russ, “Detection of atmospheric methane using a 2 wavelength He–Ne laser system,” M.S. thesis (Massachusetts Institute of Technology, Cambridge, Mass., 1978).
  4. C. B. Moore, “Gas-laser frequency selection by molecular absorption,” Appl. Opt. 4, 252–253 (1965).
    [Crossref]
  5. K. Uehara, “Alternate intensity modulation of a dual-wavelength He–Ne laser for differential absorption measurements,” Appl. Phys. B 38, 37–40 (1985).
    [Crossref]
  6. Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
    [Crossref]
  7. J. B. McManus, P. L. Kebabian, C. E. Kolb, “Atmospheric methane measurement instrument using a Zeeman-split He–Ne laser,” Appl. Opt. 28, 5016–5023 (1989).
    [Crossref] [PubMed]
  8. F. Bretenaker, A. Le Floch, “Laser eigenstates in the framework of a spatially generalized Jones matrix formalism,” J. Opt. Soc. Am. B 8, 230–238 (1991); J. Opt. Soc. Am. B 9, 2295 (1992).
    [Crossref]
  9. N. H. Tran, T. Foucher, P. Lagoutte, C. Migault, F. Bretenaker, A. Le Floch, “Heterodyne spectroscopy with spatially resolved laser eigenstates,” Opt. Lett. 18, 2056–2058 (1993).
    [Crossref] [PubMed]
  10. Here we have used the matrix convention (top and bottom) inverted from that of Ref. 8.
  11. V. S. Letokhov, V. P. Chebotayev, Nonlinear Laser Spectroscopy (Springer-Verlag, Berlin, 1977).

1993 (2)

1991 (2)

F. Bretenaker, A. Le Floch, “Laser eigenstates in the framework of a spatially generalized Jones matrix formalism,” J. Opt. Soc. Am. B 8, 230–238 (1991); J. Opt. Soc. Am. B 9, 2295 (1992).
[Crossref]

Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
[Crossref]

1989 (1)

1986 (1)

1985 (1)

K. Uehara, “Alternate intensity modulation of a dual-wavelength He–Ne laser for differential absorption measurements,” Appl. Phys. B 38, 37–40 (1985).
[Crossref]

1965 (1)

Aizawa, M.

Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
[Crossref]

Bretenaker, F.

Chanton, J. P.

G. J. Whiting, J. P. Chanton, “Primary production control of methane emission from wetlands,” Nature (London) 364, 794–795 (1993).
[Crossref]

Chebotayev, V. P.

V. S. Letokhov, V. P. Chebotayev, Nonlinear Laser Spectroscopy (Springer-Verlag, Berlin, 1977).

Foucher, T.

Grant, W. B.

Kebabian, P. L.

Kolb, C. E.

Lagoutte, P.

Le Floch, A.

Letokhov, V. S.

V. S. Letokhov, V. P. Chebotayev, Nonlinear Laser Spectroscopy (Springer-Verlag, Berlin, 1977).

Maruyama, A.

Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
[Crossref]

McManus, J. B.

Migault, C.

Moore, C. B.

Nagai, H.

Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
[Crossref]

Okamoto, T.

Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
[Crossref]

Russ, R. M.

R. M. Russ, “Detection of atmospheric methane using a 2 wavelength He–Ne laser system,” M.S. thesis (Massachusetts Institute of Technology, Cambridge, Mass., 1978).

Shimose, Y.

Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
[Crossref]

Tran, N. H.

Uehara, K.

K. Uehara, “Alternate intensity modulation of a dual-wavelength He–Ne laser for differential absorption measurements,” Appl. Phys. B 38, 37–40 (1985).
[Crossref]

Whiting, G. J.

G. J. Whiting, J. P. Chanton, “Primary production control of methane emission from wetlands,” Nature (London) 364, 794–795 (1993).
[Crossref]

Appl. Opt. (3)

Appl. Phys. B (1)

K. Uehara, “Alternate intensity modulation of a dual-wavelength He–Ne laser for differential absorption measurements,” Appl. Phys. B 38, 37–40 (1985).
[Crossref]

IEEE Photon. Lett. (1)

Y. Shimose, T. Okamoto, A. Maruyama, M. Aizawa, H. Nagai, “Remote sensing of methane gas by differential absorption measurement using a wavelength tunable DFB LD,” IEEE Photon. Lett. 3, 86–87 (1991).
[Crossref]

J. Opt. Soc. Am. B (1)

Nature (London) (1)

G. J. Whiting, J. P. Chanton, “Primary production control of methane emission from wetlands,” Nature (London) 364, 794–795 (1993).
[Crossref]

Opt. Lett. (1)

Other (3)

Here we have used the matrix convention (top and bottom) inverted from that of Ref. 8.

V. S. Letokhov, V. P. Chebotayev, Nonlinear Laser Spectroscopy (Springer-Verlag, Berlin, 1977).

R. M. Russ, “Detection of atmospheric methane using a 2 wavelength He–Ne laser system,” M.S. thesis (Massachusetts Institute of Technology, Cambridge, Mass., 1978).

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Figures (4)

Fig. 1
Fig. 1

(a) Experimental laser used to produce the two simultaneously spatially resolved laser lines λabs and λref. R1, R2, rutile crystals; M1, M2, end mirrors. Note the 7.5-mm spatial separation of the two eigenaxes between R2 and M2 and the presence of an intracavity absorption cell of CH4 on the ordinary axis. (b) Experimental arrangement used for the differential absorption measurement of methane.

Fig. 2
Fig. 2

(a) Output intensity versus cavity frequency (ν axis, 54.5 MHz/div) of the extraordinary, λabs (bottom) and the ordinary, λref (top) curves. The two gain profiles have been superimposed by slightly tilting one of the rutile crystals. (b) Modulation at two different frequencies f1 and f2 (f1/f2 = 6/5) of the intensities of the two simultaneous spatially resolved eigenstates set to the peaks of their gain curves (time axis, 2 ms/div).

Fig. 3
Fig. 3

Time evolution of the intensity on the extraordinary (λabs) and the ordinary (λref) eigenstates when methane gas is introduced into the external absorption cell (horizontal axis, 2.5 s/division). (a) 30 mTorr of methane in vacuum, (b) 3 mTorr of methane in vacuum, (c) 50 mTorr of methane in 1 atm of air (15 parts in 106/m). In (b) and (c) the vertical scale has been magnified by a factor of 7.5 with respect to (a). Note in (c) the small residual absorption of the ordinary eigenstate in the wing of the homogeneously broadened CH4 resonance.

Fig. 4
Fig. 4

Absorption (%) versus pressure (mTorr) of methane in vacuum (circles) and in 1 atm of air (triangles) in the 25-cm-long external cell.

Equations (5)

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M = H [ exp ( 2 i ϕ o ) 0 0 0 0 0 0 0 0 0 0 0 0 0 0 exp ( 2 i ϕ e ) ] A [ g abs ( ω ) + g ref ( ω ) ] ,
A = [ a ( ω ) 0 0 0 0 a ( ω ) 0 0 0 0 1 0 0 0 0 1 ] ,
g abs ( ω ) = g 0 , abs exp [ ( ω ω 0 , abs k u ) 2 ] ,
g ref ( ω ) = g 0 , ref exp [ ( ω ω 0 , ref k u ) 2 ] ,
M = H [ a ( ω ) exp ( 2 i ϕ o ) [ g abs ( ω ) + g ref ( ω ) ] 0 0 0 0 0 0 0 0 0 0 0 0 0 0 exp ( 2 i ϕ e ) [ g abs ( ω ) + g ref ( ω ) ] ] .

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