Abstract

Theoretical and experimental evaluation of three low-level photodetection techniques, namely, lock-in, noise-voltage, and electron-pulse counting are presented. The 992 cm−1 Raman band of benzene excited by a 4.2-mW He–Ne laser operating at 6328 Å provided a weak light signal which was detected by an EMI 9558 A, cooled photomultiplier. The electron-pulse-counting method employing a pulse-height discriminator was found to be superior to the other methods with regard to both signal sensitivity and signal-to-noise ratio.

© 1968 Optical Society of America

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References

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  1. A. Van Der Ziel, Noise (Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1954), Ch. 13.
  2. R. C. A. Phototubes and Photocells, Technical Manual PT-60, 1963.
  3. Y. H. Pao, R. N. Zitter, and J. E. Griffiths, Bull. Am. Phys. Soc. 11, 111 (1966).
  4. Y. H. Pao, R. N. Zitter, and J. E. Griffiths, J. Opt. Soc. Am. 56, 1133 (1966).
    [CrossRef]
  5. E. H. Eberhardt, IEEE Trans. Nucl. Sci. NS-11(3), 48 (1964).
    [CrossRef]
  6. R. F. Tusting, Q. A. Kerns, and H. K. Knudsen, IEEE Trans. Nucl. Sci. NS-9(3), 118 (1962).

1966 (2)

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, Bull. Am. Phys. Soc. 11, 111 (1966).

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, J. Opt. Soc. Am. 56, 1133 (1966).
[CrossRef]

1964 (1)

E. H. Eberhardt, IEEE Trans. Nucl. Sci. NS-11(3), 48 (1964).
[CrossRef]

1963 (1)

R. C. A. Phototubes and Photocells, Technical Manual PT-60, 1963.

1962 (1)

R. F. Tusting, Q. A. Kerns, and H. K. Knudsen, IEEE Trans. Nucl. Sci. NS-9(3), 118 (1962).

Eberhardt, E. H.

E. H. Eberhardt, IEEE Trans. Nucl. Sci. NS-11(3), 48 (1964).
[CrossRef]

Griffiths, J. E.

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, J. Opt. Soc. Am. 56, 1133 (1966).
[CrossRef]

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, Bull. Am. Phys. Soc. 11, 111 (1966).

Kerns, Q. A.

R. F. Tusting, Q. A. Kerns, and H. K. Knudsen, IEEE Trans. Nucl. Sci. NS-9(3), 118 (1962).

Knudsen, H. K.

R. F. Tusting, Q. A. Kerns, and H. K. Knudsen, IEEE Trans. Nucl. Sci. NS-9(3), 118 (1962).

Pao, Y. H.

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, J. Opt. Soc. Am. 56, 1133 (1966).
[CrossRef]

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, Bull. Am. Phys. Soc. 11, 111 (1966).

Tusting, R. F.

R. F. Tusting, Q. A. Kerns, and H. K. Knudsen, IEEE Trans. Nucl. Sci. NS-9(3), 118 (1962).

Van Der Ziel, A.

A. Van Der Ziel, Noise (Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1954), Ch. 13.

Zitter, R. N.

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, Bull. Am. Phys. Soc. 11, 111 (1966).

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, J. Opt. Soc. Am. 56, 1133 (1966).
[CrossRef]

Bull. Am. Phys. Soc. (1)

Y. H. Pao, R. N. Zitter, and J. E. Griffiths, Bull. Am. Phys. Soc. 11, 111 (1966).

IEEE Trans. Nucl. Sci. (2)

E. H. Eberhardt, IEEE Trans. Nucl. Sci. NS-11(3), 48 (1964).
[CrossRef]

R. F. Tusting, Q. A. Kerns, and H. K. Knudsen, IEEE Trans. Nucl. Sci. NS-9(3), 118 (1962).

J. Opt. Soc. Am. (1)

R. C. A. Phototubes and Photocells (1)

R. C. A. Phototubes and Photocells, Technical Manual PT-60, 1963.

Other (1)

A. Van Der Ziel, Noise (Prentice-Hall, Inc., Englewood Cliffs, New Jersey, 1954), Ch. 13.

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Figures (5)

Fig. 1
Fig. 1

Diagram of the lock-in detection technique for 90° Raman scattering.

Fig. 2
Fig. 2

Response of the lock-in, noise-voltage, and pulse-counting methods to the 992 cm−1 Raman band in benzene. Upper traces refer to observed signals with shutter open, lower traces refer to signal with shutter closed. (a) Lock-in; S/N=8.2, RL=1 meg, Bf=1/10 cps, G=5×104, S=3.1 V, N=0.38 V. (b) Noise-voltage; S/N=27, RL=1 meg, Bf=1/13 cps, G=1.5×103, S=200 mV, N=7.5 mV. (c) Pulse counting; S/N=32, RL=1 meg, τ0=10 sec, G=104, n=620 cps, nd=40 cps, E=0.15 V.

Fig. 3
Fig. 3

Diagram of the noise-voltage technique for 90° Raman scattering.

Fig. 4
Fig. 4

Diagram of the pulse-counting technique for 90° Raman scattering.

Fig. 5
Fig. 5

(a) Distribution of pulse heights per sec above a discriminating bias voltage for a cooled EMI 9558 A photomultiplier operating at 1250 V; (b) Enlargement of the small pulse-height region, vertical line refers to pulse height for maximum signal-to-noise ratio. In (b), the dashed curve refers to expected behavior at low bias voltages which could not be observed. △ Dark current, nd; □ Dark and Raman signal count, n=ns+nd; ○ Raman signal, ns; τ=10 sec.

Tables (1)

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Table I Theoretical and experimental results on detection of the 992 cm−1 Raman band in benzene.

Equations (24)

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S / N = ( 4 V 2 / W 0 B f ) 1 2 ,
V N = ( W 0 B s ) 1 2
S / N = ( 4 V 2 B s / V N 2 B f ) 1 2 ,
V = R L I A M ,
V N R L [ 2 e ( μ I A + μ I d ) B s ] 1 2
S / N [ 2 I A 2 / e μ B f ( I A + I d ) ] 1 2 .
I A = S / G R L ,
I d = [ 2 I A 2 / e μ B f ( S / N ) 2 ] - I A .
I A = 6.0 × 10 - 11 A I d = 2.3 × 10 - 10 A .
S N = ( 8 ) ( V 1 - V 2 ) / ( B f W 01 ) 1 2 ,
V N = ( W 01 B s ) 1 2 .
S N = V 1 - V 2 V N ( 8 B s B f ) 1 2 .
V 1 A G R L ( I A + I d ) ,
V 2 A G R L I d ,
V N A G R L [ 2 e μ ( I A + I d ) B s ] 1 2 .
S / N [ 4 I A 2 / e μ ( I A + I d ) B f ] 1 2 .
I A S / A G R L .
I A 16     × 10 - 11 A I d =     3.1 × 10 - 10 A .
S = ( n - n d ) τ .
N = ( n τ ) 1 2 .
S / N = ( n - n d ) τ / ( n τ ) 1 2 = n s τ / [ ( n s + n d ) τ ] 1 2
( I A ) min = ( n s ) min e μ ~ 3.2 × 10 - 13 A ,
( I A ) ( n s ) max e μ ( 650 ) ( 1.6 × 10 - 19 ) ( 10 6 ) = 10.4 × 10 - 11 A .
I d n d e μ ( 40 ) ( 1.6 × 10 - 19 ) ( 10 6 ) = 6.4 × 10 - 12 A ,