Abstract

The method of doing dual-beam single-detector wavelength-modulation spectroscopy originally proposed by Bonfiglioli and Trench is demonstrated experimentally, using a tunable laser. This system monitors both the reference and the sample beams continuously in phase quadrature and measures the derivative and the direct spectra simultaneously. When this system was used in conjunction with an electro-optically tuned cw dye laser, a sensitivity of (1/T) (dT/dλ) = 3 × 10−6 Å−1 was experimentally achieved for modulation depths from 1 to 50 Å and can be extended down to 0.1 Å. The derivative spectrum corresponding to the extremely weak fifth overtone of the CH stretching vibration in the electronic ground state of benzene has been observed in a path length as short as 1 cm.

© 1977 Optical Society of America

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References

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  1. M. Cardona, Modulation Spectroscopy, Supplement 11 of Solid State Physics, F. Seitz, D. Turnbull, eds. (Academic, New York, 1969).
  2. G. Bonfiglioli, P. Brovetto, Appl. Opt., 3, 1417 (1964).
    [CrossRef]
  3. M. Welkowsky, R. Braunstein, Rev. Sci. Instrum. 43, 399 (1972).
    [CrossRef]
  4. G. Bonfiglioli, J. Trench, Opt. Comm. 10, 207 (1974).
    [CrossRef]
  5. J. M. Telle, C. L. Tang, Appl. Phys. Lett. 24, 85 (1974).
    [CrossRef]
  6. C. L. Tang, J. M. Telle, J. Appl. Phys. 45, 4503 (1974).
    [CrossRef]
  7. M. E. Long, R. L. Swofford, A. C. Albrecht, Science 191, 183 (1976).
    [CrossRef] [PubMed]

1976 (1)

M. E. Long, R. L. Swofford, A. C. Albrecht, Science 191, 183 (1976).
[CrossRef] [PubMed]

1974 (3)

G. Bonfiglioli, J. Trench, Opt. Comm. 10, 207 (1974).
[CrossRef]

J. M. Telle, C. L. Tang, Appl. Phys. Lett. 24, 85 (1974).
[CrossRef]

C. L. Tang, J. M. Telle, J. Appl. Phys. 45, 4503 (1974).
[CrossRef]

1972 (1)

M. Welkowsky, R. Braunstein, Rev. Sci. Instrum. 43, 399 (1972).
[CrossRef]

1964 (1)

Albrecht, A. C.

M. E. Long, R. L. Swofford, A. C. Albrecht, Science 191, 183 (1976).
[CrossRef] [PubMed]

Bonfiglioli, G.

G. Bonfiglioli, J. Trench, Opt. Comm. 10, 207 (1974).
[CrossRef]

G. Bonfiglioli, P. Brovetto, Appl. Opt., 3, 1417 (1964).
[CrossRef]

Braunstein, R.

M. Welkowsky, R. Braunstein, Rev. Sci. Instrum. 43, 399 (1972).
[CrossRef]

Brovetto, P.

Cardona, M.

M. Cardona, Modulation Spectroscopy, Supplement 11 of Solid State Physics, F. Seitz, D. Turnbull, eds. (Academic, New York, 1969).

Long, M. E.

M. E. Long, R. L. Swofford, A. C. Albrecht, Science 191, 183 (1976).
[CrossRef] [PubMed]

Swofford, R. L.

M. E. Long, R. L. Swofford, A. C. Albrecht, Science 191, 183 (1976).
[CrossRef] [PubMed]

Tang, C. L.

J. M. Telle, C. L. Tang, Appl. Phys. Lett. 24, 85 (1974).
[CrossRef]

C. L. Tang, J. M. Telle, J. Appl. Phys. 45, 4503 (1974).
[CrossRef]

Telle, J. M.

C. L. Tang, J. M. Telle, J. Appl. Phys. 45, 4503 (1974).
[CrossRef]

J. M. Telle, C. L. Tang, Appl. Phys. Lett. 24, 85 (1974).
[CrossRef]

Trench, J.

G. Bonfiglioli, J. Trench, Opt. Comm. 10, 207 (1974).
[CrossRef]

Welkowsky, M.

M. Welkowsky, R. Braunstein, Rev. Sci. Instrum. 43, 399 (1972).
[CrossRef]

Appl. Opt. (1)

Appl. Phys. Lett. (1)

J. M. Telle, C. L. Tang, Appl. Phys. Lett. 24, 85 (1974).
[CrossRef]

J. Appl. Phys. (1)

C. L. Tang, J. M. Telle, J. Appl. Phys. 45, 4503 (1974).
[CrossRef]

Opt. Comm. (1)

G. Bonfiglioli, J. Trench, Opt. Comm. 10, 207 (1974).
[CrossRef]

Rev. Sci. Instrum. (1)

M. Welkowsky, R. Braunstein, Rev. Sci. Instrum. 43, 399 (1972).
[CrossRef]

Science (1)

M. E. Long, R. L. Swofford, A. C. Albrecht, Science 191, 183 (1976).
[CrossRef] [PubMed]

Other (1)

M. Cardona, Modulation Spectroscopy, Supplement 11 of Solid State Physics, F. Seitz, D. Turnbull, eds. (Academic, New York, 1969).

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Figures (2)

Fig. 1
Fig. 1

Schematic diagram of spectrometer: EOL, electro-optically tunable laser; BS1, BS2, beam splitters; M1, M2, plane mirrors; C, chopper; S, sample; D, detector; MULT, multiplier module; VLIA, vector lock-in amplifier; LPF, low-pass filter; LPC, low-pass comparator; FBIP, FBQ, ac normalization feedback circuits; LIA, lock-in amplifier; RV, scanning ramp voltage; Vc comparator control voltage. T marks the output point for direct-absorption spectrum.

Fig. 2
Fig. 2

(a) Derivative spectrum of benzene. (b) Absorption spectrum of benzene using thermal lens technique. (See Ref. 7.)

Equations (3)

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1 C d C d λ Δλ = ( 1 I d I d λ + 1 G d G d λ ) Δλ + 1 T d T d λ Δλ ,
V Q I G T + [ ( d I d λ G + d G d λ I ) T + I G d T d λ ] Δλ ( t ) , V I P I G + ( d I d λ G + d G d λ I ) Δλ ( t ) .
N Q V Q 1 + ( 1 I d I d λ + 1 G d G d λ + 1 T d T d λ ) Δλ ( t ) , N I P V I P 1 + ( 1 I d I d λ + 1 G d G d λ ) Δλ ( t ) .

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