Abstract

A two-mirror multipass absorption cell that is operated open to the atmosphere from a stratospheric balloon to monitor in situ methane (in the 1.65-µm region) and water vapor (in the 1.39-µm region) with telecommunication laser diodes is described. A small Cassegrain-type telescope is used to couple the cell simultaneously with two near-infrared InGaAsP laser diodes by means of optical fibers. The 1-m cell provides an absorption path length of 56 m. The optical cell was carefully designed to be free of incidental fringing in the 10-5 absorption range. It is used in combination with a dual-beam detector to obtain a detection limit of 10-5 absorption units, a large dynamic range of the measurements of many orders of magnitude, and a precision error in the concentration determination of a few percents. The optical arrangement of the cell and its ability to be used to detect in situ trace gas in the stratosphere, in severe environmental conditions, are exposed.

© 2002 Optical Society of America

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References

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  1. R. D. May, “Open-path near-IR tunable diode laser spectrometer for atmospheric measurements of H2O,” J. Geophys. Res. 103, 19161–19172 (1998).
    [CrossRef]
  2. J. A. Silver, D. C. Hovde, “Near-infrared diode laser airborne hygrometer,” Rev. Sci. Instrum. 65, 1691–1694 (1994).
    [CrossRef]
  3. K. Uehara, H. Tai, “Remote detection of methane with a 1.66-µm diode laser,” Appl. Opt. 31, 809–814 (1992).
    [CrossRef] [PubMed]
  4. C. R. Webster, R. D. May, C. A. Trimble, R. G. Chave, J. Kendall, “Aircraft (ER-2) laser infrared absorption spectrometer (ALIAS) for in situ stratospheric measurements of HCl, N2O, CH4, NO2, and HNO3,” Appl. Opt. 33, 454–472 (1994).
    [CrossRef] [PubMed]
  5. G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
    [CrossRef]
  6. G. Toci, P. Mazzinghi, M. Vannini, “A diode laser spectrometer for the in situ measurement of the HNO3 content of polar stratospheric clouds,” J. Atmos. Ocean. Tech. 16, 1295–1302 (1999).
    [CrossRef]
  7. D. C. Scott, R. L. Herman, C. R. Webster, R. D. May, G. J. Flesh, E. J. Moyer, “Airborne laser infrared absorption spectrometer (ALIAS-II) for in situ atmospheric measurements of N2O, CH4, CO, HCl, and NO2 from balloon or remotely piloted aircraft platforms,” Appl. Opt. 38, 4609–4622 (1999).
    [CrossRef]
  8. G. Durry, G. Megie, “Atmospheric CH4 and H2O monitoring with near-infrared InGaAs laser diodes by the SDLA, a balloonborne spectrometer for tropospheric and stratospheric in situ measurements,” Appl. Opt. 38, 7342–7354 (1999).
    [CrossRef]
  9. G. Durry, I. Pouchet, N. Amarouche, T. Danguy, G. Megie, “Shot-noise-limited dual-beam detector for atmospheric trace-gas monitoring with near-infrared diode lasers,” Appl. Opt. 39, 5609–5619 (2000).
    [CrossRef]
  10. C. R. Webster, “Brewster-plate spoiler: a novel method for reducing the amplitude of interference fringes that limit tunable-laser absorption sensitivities,” J. Opt. Soc. Am. B 2, 1464–1470 (1985).
    [CrossRef]
  11. J. A. Silver, A. C. Stanton, “Optical interference fringe reduction in laser absorption experiments,” Appl. Opt. 27, 1914–1916 (1988).
    [CrossRef] [PubMed]
  12. J. B. McManus, P. L. Kebabian, “Narrow optical interference fringes for certain setup conditions in multipass absorption cells of the Herriott type,” Appl. Opt. 29, 898–900 (1990).
    [CrossRef] [PubMed]
  13. G. Durry, G. Megie, “In situ measurements of H2O from a stratospheric balloon by diode laser direct-differential absorption spectroscopy at 1.39 µm,” Appl. Opt. 39, 5601–5608 (2000).
    [CrossRef]
  14. D. R. Herriott, H. Kogelnik, R. Kompfer, “Off-axis paths in spherical mirror interferometers,” Appl. Opt. 3, 523–526 (1964).
    [CrossRef]
  15. J. Altmann, R. Baumgart, C. Weitkamp, “Two-mirror multipass absorption cell,” Appl. Opt. 20, 995–999 (1981).
    [CrossRef] [PubMed]
  16. G. Durry, “Balloonborne near-infrared diode laser spectroscopy for in situ measurements of atmospheric CH4 and H2O,” Spectrochim. Acta Part A 57/9, 1855–1863 (2001).

2001 (1)

G. Durry, “Balloonborne near-infrared diode laser spectroscopy for in situ measurements of atmospheric CH4 and H2O,” Spectrochim. Acta Part A 57/9, 1855–1863 (2001).

2000 (2)

1999 (3)

1998 (2)

R. D. May, “Open-path near-IR tunable diode laser spectrometer for atmospheric measurements of H2O,” J. Geophys. Res. 103, 19161–19172 (1998).
[CrossRef]

G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
[CrossRef]

1994 (2)

1992 (1)

1990 (1)

1988 (1)

1985 (1)

1981 (1)

1964 (1)

Altmann, J.

Amarouche, N.

Baumgart, R.

Chave, R. G.

Danguy, T.

Durry, G.

Flesh, G. J.

Harris, G. W.

G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
[CrossRef]

Herman, R. L.

Herriott, D. R.

Hovde, D. C.

J. A. Silver, D. C. Hovde, “Near-infrared diode laser airborne hygrometer,” Rev. Sci. Instrum. 65, 1691–1694 (1994).
[CrossRef]

Iguchi, T.

G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
[CrossRef]

Kebabian, P. L.

Kendall, J.

Kogelnik, H.

Kompfer, R.

Mackay, G. I.

G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
[CrossRef]

May, R. D.

Mayne, L. K.

G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
[CrossRef]

Mazzinghi, P.

G. Toci, P. Mazzinghi, M. Vannini, “A diode laser spectrometer for the in situ measurement of the HNO3 content of polar stratospheric clouds,” J. Atmos. Ocean. Tech. 16, 1295–1302 (1999).
[CrossRef]

McManus, J. B.

Megie, G.

Moyer, E. J.

Pouchet, I.

Schiff, H. I.

G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
[CrossRef]

Scott, D. C.

Silver, J. A.

J. A. Silver, D. C. Hovde, “Near-infrared diode laser airborne hygrometer,” Rev. Sci. Instrum. 65, 1691–1694 (1994).
[CrossRef]

J. A. Silver, A. C. Stanton, “Optical interference fringe reduction in laser absorption experiments,” Appl. Opt. 27, 1914–1916 (1988).
[CrossRef] [PubMed]

Stanton, A. C.

Tai, H.

Toci, G.

G. Toci, P. Mazzinghi, M. Vannini, “A diode laser spectrometer for the in situ measurement of the HNO3 content of polar stratospheric clouds,” J. Atmos. Ocean. Tech. 16, 1295–1302 (1999).
[CrossRef]

Trimble, C. A.

Uehara, K.

Vannini, M.

G. Toci, P. Mazzinghi, M. Vannini, “A diode laser spectrometer for the in situ measurement of the HNO3 content of polar stratospheric clouds,” J. Atmos. Ocean. Tech. 16, 1295–1302 (1999).
[CrossRef]

Webster, C. R.

Weitkamp, C.

Appl. Opt. (10)

K. Uehara, H. Tai, “Remote detection of methane with a 1.66-µm diode laser,” Appl. Opt. 31, 809–814 (1992).
[CrossRef] [PubMed]

C. R. Webster, R. D. May, C. A. Trimble, R. G. Chave, J. Kendall, “Aircraft (ER-2) laser infrared absorption spectrometer (ALIAS) for in situ stratospheric measurements of HCl, N2O, CH4, NO2, and HNO3,” Appl. Opt. 33, 454–472 (1994).
[CrossRef] [PubMed]

D. C. Scott, R. L. Herman, C. R. Webster, R. D. May, G. J. Flesh, E. J. Moyer, “Airborne laser infrared absorption spectrometer (ALIAS-II) for in situ atmospheric measurements of N2O, CH4, CO, HCl, and NO2 from balloon or remotely piloted aircraft platforms,” Appl. Opt. 38, 4609–4622 (1999).
[CrossRef]

G. Durry, G. Megie, “Atmospheric CH4 and H2O monitoring with near-infrared InGaAs laser diodes by the SDLA, a balloonborne spectrometer for tropospheric and stratospheric in situ measurements,” Appl. Opt. 38, 7342–7354 (1999).
[CrossRef]

G. Durry, I. Pouchet, N. Amarouche, T. Danguy, G. Megie, “Shot-noise-limited dual-beam detector for atmospheric trace-gas monitoring with near-infrared diode lasers,” Appl. Opt. 39, 5609–5619 (2000).
[CrossRef]

J. A. Silver, A. C. Stanton, “Optical interference fringe reduction in laser absorption experiments,” Appl. Opt. 27, 1914–1916 (1988).
[CrossRef] [PubMed]

J. B. McManus, P. L. Kebabian, “Narrow optical interference fringes for certain setup conditions in multipass absorption cells of the Herriott type,” Appl. Opt. 29, 898–900 (1990).
[CrossRef] [PubMed]

G. Durry, G. Megie, “In situ measurements of H2O from a stratospheric balloon by diode laser direct-differential absorption spectroscopy at 1.39 µm,” Appl. Opt. 39, 5601–5608 (2000).
[CrossRef]

D. R. Herriott, H. Kogelnik, R. Kompfer, “Off-axis paths in spherical mirror interferometers,” Appl. Opt. 3, 523–526 (1964).
[CrossRef]

J. Altmann, R. Baumgart, C. Weitkamp, “Two-mirror multipass absorption cell,” Appl. Opt. 20, 995–999 (1981).
[CrossRef] [PubMed]

J. Atmos. Chem. (1)

G. W. Harris, G. I. Mackay, T. Iguchi, L. K. Mayne, H. I. Schiff, “Measurements of formaldehyde in the troposphere by tunable diode laser absorption spectroscopy,” J. Atmos. Chem. 8, 119–137 (1998).
[CrossRef]

J. Atmos. Ocean. Tech. (1)

G. Toci, P. Mazzinghi, M. Vannini, “A diode laser spectrometer for the in situ measurement of the HNO3 content of polar stratospheric clouds,” J. Atmos. Ocean. Tech. 16, 1295–1302 (1999).
[CrossRef]

J. Geophys. Res. (1)

R. D. May, “Open-path near-IR tunable diode laser spectrometer for atmospheric measurements of H2O,” J. Geophys. Res. 103, 19161–19172 (1998).
[CrossRef]

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

Rev. Sci. Instrum. (1)

J. A. Silver, D. C. Hovde, “Near-infrared diode laser airborne hygrometer,” Rev. Sci. Instrum. 65, 1691–1694 (1994).
[CrossRef]

Spectrochim. Acta Part A (1)

G. Durry, “Balloonborne near-infrared diode laser spectroscopy for in situ measurements of atmospheric CH4 and H2O,” Spectrochim. Acta Part A 57/9, 1855–1863 (2001).

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Figures (7)

Fig. 1
Fig. 1

Schematics of the SDLA near-infrared tunable diode laser spectrometer. The instrument is operated from a stratospheric balloon to take in situ methane (in the 1.65-µm spectral region) and water vapor (in the 1.39-µm spectral region) measurements at 1-s intervals by means of two InGaAsP telecommunication laser diodes. It is based on the use of a multipass optical cell open to the atmosphere that provides a 56-m absorption path length.

Fig. 2
Fig. 2

Optical layout of the multipass cell. A Cassegrain-type telescope (mirrors M 0 and M 1) is used to inject the laser beam in the multipass absorption cell (mirrors M 2 and M 3) and to collect the laser beam exiting the cell. Two laser diodes are simultaneously coupled to the cell by means of the telescope; perpendicular to the figure plane, the same injection–detection scheme is used for the second laser diode. The optical cell is used in conjunction with a differential detection set-up; a differential spectrum is constructed from the balanced difference between a reference and a sample signal (containing the absorption information) recorded at the input and the output of the optical cell.

Fig. 3
Fig. 3

Coordinate system (x, y, z, z′). (a) z′ is the optical axis of the Cassegrain-type telescope; z is the optical axis of the two-mirror multipass cell. (b) Two lasers are coupled simultaneously with the optical cell (channels 1 and 2). The detectors and optical fibers associated with channels 1 and 2 are disposed symmetrically with respect to the x axis. The coupling hole is located at a distance x 0 from the center of the cell front mirror.

Fig. 4
Fig. 4

Successive laser beam spots over the surface of the cell front mirror (M 2). After entering the cell, the laser light produces a series of 28 reflex spots lying upon an ellipse on each mirror. Both ellipses, which correspond to the two laser beams propagating simultaneously in the multipass cell, are made perpendicular by means of an appropriate design of the coupling telescope. After 56 transits in the cell, both laser beams exit the cell through the coupling hole (spot 56 in the figure) and are collected by the telescope, each to be focused on a dedicated detector.

Fig. 5
Fig. 5

Methane and water vapor absorption spectra obtained with the SDLA in the stratosphere during a balloon flight in southern France on 10 May 1999. Differential detection was used in conjunction with the open multipass cell to obtain the spectra. (a) Spectra at the input (B) and the output (A) of the optical cell are recorded to carry the intensity calibration. (b) To extract the weak methane absorption information (at 17 km, approximately 0.25% of the laser energy is absorbed in the cell by ambient methane), we construct the differential spectrum from the analogical difference between signals A and B. (c) Methane molecular absorption is then extracted from the differential spectrum. The mixing ratio is obtained from a nonlinear least-squares fit to the full molecular line shape in combination with the pressure and temperature measurements and with the HITRAN database. (d) Similarly, the stratospheric water vapor spectrum was obtained by differential absorption spectroscopy from the second channel of the optical cell. Both channels were found free of interference fringes in the 10-5 absorption range.

Fig. 6
Fig. 6

Optical multipass cell used with the SDLA. The cell is operated open to the atmosphere from a stratospheric balloon. Two optical fibers are connected to the cell to inject the near-infrared laser beams by means of a small telescope. Invar tubes are combined to maintain both gold-coated spherical mirrors of the multipass cell at a distance of approximately 1 m.

Fig. 7
Fig. 7

Methane vertical concentration profiles restituted in the lower stratosphere by the SDLA during a flight in southern France on 10 May 1999. Profiles obtained at ascent and descent of the gondola are illustrated; a constant offset (equal to 0.3 parts per million) was added to the measurements made during the descent for the sake of clarity. The vertical profiles are made of approximately seven thousand concentration measurements that were obtained through the processing of the in situ spectra achieved by means of the open multipass cell (see Fig. 5).

Equations (12)

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fc=R024l+2R0-R1-R02.
α=2h2lR0R1+1R1-1R0,
xn=x0 cosnθ+d4f-d1/2x0+2fx0sinnθ,
cosθ=1-d2f.
Nθ=2πM,
d=2f1-cos2π MN.
xn=A sinnθ+Ψ, yn=B sinnθ,
A2=4f4f-dx02+dx0x0+dfx02,B2=4f4f-ddfy02
tanΨ=4fd-11/21+2f x0x0.
x0=tanαsinΦ, y0=tanαcosΦ.
xN-1=x0f+x0, yN-1=y0.
xN-1=tanαsinΦ, yN-1=tanαcosΦ.

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