Abstract

A new detection technique for photothermal deflection spectroscopy and photoacoustic deflection spectroscopy is presented. The technique uses a pair of matched multiple slits placed in the path of the probe beam and oriented to block the probe light from the detector in the absence of a deflection signal. Significant improvement in the signal-to-noise ratio and in the frequency bandwidth compared with those available with current techniques is demonstrated.

© 2005 Optical Society of America

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References

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  1. J. A. Sell, ed., Photothermal Investigations of Solids and Fluids (Academic, New York, 1989).
  2. A. Mandelis, ed., Principles and Perspectives of Photothermal and Photoacoustic Phenomena, Vol. 1 of Progress in Photothermal and Photoacoustic Science and Technology (North-Holland, New York, 1991).
  3. See, for example, the Proceedings of the 12th International Conference on Photoacoustic and Photothermal Phenomena, Rev. Sci. Instrum.74, 285–914 (2003).
  4. See, for example R. Gupta, in Photothermal Investigations of Solids and Fluids, J. A. Sell, ed. (Academic, New York, 1989), Chap. 3.
  5. A. Rose, G. J. Salamo, R. Gupta, “Photoacoustic deflection spectroscopy: a new species-specific method for combustion diagnostics,” Appl. Opt. 23, 781–784 (1984).
    [CrossRef] [PubMed]
  6. W. Zapka, P. Pokrowsky, A. C. Tam, “Optoacoustic laser deflection (OLD) technique for temperature measurements,” Opt. Lett. 7, 477–479 (1982).
    [CrossRef] [PubMed]
  7. A. Rose, R. Vyas, R. Gupta, “Pulsed photothermal deflection spectroscopy in a flowing medium: a quantitative investigation,” Appl. Opt. 25, 4626–4643 (1986).
    [CrossRef] [PubMed]
  8. Y. Li, R. Gupta, “Simultaneous measurement of absolute OH concentration, temperature, and flow velocity in a flame by photothermal deflection spectroscopy,” Appl. Phys. B 75, 903–906 (2002).
    [CrossRef]
  9. Y. Li, R. Gupta, “Measurement of absolute minority species concentration and temperature in a flame by the photothermal deflection spectroscopy technique,” Appl. Opt. 42, 2226–2234 (2003).
    [CrossRef] [PubMed]
  10. See, for example E. Hecht, A. Zajac, Optics (Addison-Wesley, Reading, Mass., 1974).
  11. A. Rose, “The development of pulsed photoacoustic and photothermal deflection spectroscopy as diagnostic tools for combustion,” Ph.D. dissertation (University of Arkansas, Fayetteville, 1986).

2003 (1)

2002 (1)

Y. Li, R. Gupta, “Simultaneous measurement of absolute OH concentration, temperature, and flow velocity in a flame by photothermal deflection spectroscopy,” Appl. Phys. B 75, 903–906 (2002).
[CrossRef]

1986 (1)

1984 (1)

1982 (1)

Gupta, R.

Hecht, E.

See, for example E. Hecht, A. Zajac, Optics (Addison-Wesley, Reading, Mass., 1974).

Li, Y.

Y. Li, R. Gupta, “Measurement of absolute minority species concentration and temperature in a flame by the photothermal deflection spectroscopy technique,” Appl. Opt. 42, 2226–2234 (2003).
[CrossRef] [PubMed]

Y. Li, R. Gupta, “Simultaneous measurement of absolute OH concentration, temperature, and flow velocity in a flame by photothermal deflection spectroscopy,” Appl. Phys. B 75, 903–906 (2002).
[CrossRef]

Pokrowsky, P.

Rose, A.

Salamo, G. J.

Tam, A. C.

Vyas, R.

Zajac, A.

See, for example E. Hecht, A. Zajac, Optics (Addison-Wesley, Reading, Mass., 1974).

Zapka, W.

Appl. Opt. (3)

Appl. Phys. B (1)

Y. Li, R. Gupta, “Simultaneous measurement of absolute OH concentration, temperature, and flow velocity in a flame by photothermal deflection spectroscopy,” Appl. Phys. B 75, 903–906 (2002).
[CrossRef]

Opt. Lett. (1)

Other (6)

See, for example E. Hecht, A. Zajac, Optics (Addison-Wesley, Reading, Mass., 1974).

A. Rose, “The development of pulsed photoacoustic and photothermal deflection spectroscopy as diagnostic tools for combustion,” Ph.D. dissertation (University of Arkansas, Fayetteville, 1986).

J. A. Sell, ed., Photothermal Investigations of Solids and Fluids (Academic, New York, 1989).

A. Mandelis, ed., Principles and Perspectives of Photothermal and Photoacoustic Phenomena, Vol. 1 of Progress in Photothermal and Photoacoustic Science and Technology (North-Holland, New York, 1991).

See, for example, the Proceedings of the 12th International Conference on Photoacoustic and Photothermal Phenomena, Rev. Sci. Instrum.74, 285–914 (2003).

See, for example R. Gupta, in Photothermal Investigations of Solids and Fluids, J. A. Sell, ed. (Academic, New York, 1989), Chap. 3.

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Figures (10)

Fig. 1
Fig. 1

Illustration of multiple-slit conjugate masks.

Fig. 2
Fig. 2

Schematic illustration of the experiment: L1–L4, lenses; m1–m4, mirrors; M1, M2, masks; DC, dye cuvette; PM, powermeter; QD, quadrant detector; DA, difference amplifier; DO, digital oscilloscope; PMT, photomultiplier tube; BS, beam splitter; PD, photodiode.

Fig. 3
Fig. 3

PTDS signal observed by the conjugate-mask technique.

Fig. 4
Fig. 4

PTDS signal observed by the quadrant-detector technique. Deflection is plotted in microradians. The difference amplifier was set to the highest gain available, where the SNR was highest, at the expense of response time.

Fig. 5
Fig. 5

PTDS signal observed by the quadrant-detector technique. The difference amplifier was set to give the shortest response time, at the expense of SNR.

Fig. 6
Fig. 6

Illustration of the effect of the number of slits on the amplitude of the signal. Curves I, II, and III refer to the PTDS signal measured with one, two, and three slits exposed, respectively.

Fig. 7
Fig. 7

PADS signal, as observed by the conjugate-mask technique. The sharp spike at ∼2 µs is the PADS signal, and the broad background signal is the PTDS signal.

Fig. 8
Fig. 8

Arrangement of masks M1 and M2. The curve represents the diffraction pattern of the light produced by mask M1.

Fig. 9
Fig. 9

Dependence of the signal on the probe beam deflection for the mask geometry shown in Fig. 8.

Fig. 10
Fig. 10

Schematic diagram of the difference amplifier that was used with the quadrant detector.

Equations (9)

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Φ M = η F Φ 0 ,
F = 2 π π / 2 3 π / 2 sin 2 β β 2 d β ,
β = π b sin θ λ π b θ λ .
Δ F = 1 π ( 3 π 2 3 π 2 + Δ β sin 2 β β 2 d β + π 2 π 2 + Δ β sin 2 β β 2 d β π 2 π 2 + Δ β sin 2 β β 2 d β + 3 π 2 3 π 2 + Δ β sin 2 β β 2 d β ) ,
Δ β = π b λ φ .
( S N ) CM η Φ 0 F Δ F ,
η = 2 π a 2 d d exp [ 2 ( x 2 + y 2 ) / a 2 ] H ( cos 2 π y Δ ) d y d x ,
Δ s = 2 π a 2 [ 0 exp [ 2 ( x 2 + ( y + δ ) 2 ) / a 2 ] d y d x 0 exp [ 2 ( x 2 + ( y + δ ) 2 ) / a 2 ] d y d x ] .
( S N ) BC Φ 0 Δ s .

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