Abstract

A two-wavelength laser-diode interferometer that is based on heterodyne detection with one phasemeter has been constructed. Two laser diodes are frequency modulated by mutually inverted sawtooth currents on an unbalanced interferometer. One can measure the tested phase at a synthetic wavelength from the sum of the interference beat signals by synchronizing them with the modulation frequency. The experimental result presented shows a phase-measurement range with a 4.7-μm synthetic wavelength.

© 1995 Optical Society of America

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References

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  1. N. A. Massie, R. D. Nelson, S. Holly, Appl. Opt. 18, 1797 (1979).
    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
  3. V. Gusmeroli, M. Martinelli, Opt. Commun. 94, 309 (1992).
    [CrossRef]
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    [CrossRef] [PubMed]
  5. R. Dändliker, R. Thalman, D. Prongué, Opt. Lett. 13, 339 (1988).
    [CrossRef] [PubMed]
  6. E. Gelmini, U. Minoni, F. Docchio, Opt. Lett. 19, 213 (1994).
    [CrossRef] [PubMed]
  7. Y. Ishii, R. Onodera, Opt. Lett. 16, 1523 (1991).
    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]

1995 (1)

1994 (2)

1992 (1)

V. Gusmeroli, M. Martinelli, Opt. Commun. 94, 309 (1992).
[CrossRef]

1991 (1)

1988 (1)

1985 (1)

1979 (1)

Dändliker, R.

Docchio, F.

Fercher, A. F.

Gelmini, E.

Gusmeroli, V.

V. Gusmeroli, M. Martinelli, Opt. Commun. 94, 309 (1992).
[CrossRef]

Holly, S.

Hu, H. Z.

Ishii, Y.

Martinelli, M.

V. Gusmeroli, M. Martinelli, Opt. Commun. 94, 309 (1992).
[CrossRef]

Massie, N. A.

Minoni, U.

Nelson, R. D.

Onodera, R.

Prongué, D.

Thalman, R.

Vry, U.

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Figures (4)

Fig. 1
Fig. 1

Experimental setup for a two-wavelength LD heterodyne interferometer with one phasemeter built into a lock-in amplifier. ATC’s, automatic temperature-controlled circuits; PBS’s, polarizing beam splitters; PZT, piezoelectric transducer; FG, function generator; M-PD’s, monitor photodiodes; IF1, IF2, interference filters.

Fig. 2
Fig. 2

Phasor diagram of a bandpass-filtered signal sf (t). Phase Φ can be measured by heterodyne detection.

Fig. 3
Fig. 3

Variations in the injection currents of two LD’s (upper traces) and in the corresponding interference signals (lower traces).

Fig. 4
Fig. 4

Experimental result for an optical-path-length change longer than a wavelength, λ1. ϕ1 is the phase at wavelength λ1 with 2π ambiguities. The result for phase Φ demonstrates the actual displacement of the object mirror.

Equations (3)

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s 0 ( t ) = A 1 + A 2 + B 1 cos ( ω b 1 t + ϕ 1 ) + B 2 cos ( ω b 2 t + ϕ 2 )
ω b 1 = - ω b 2 = ω s ,
s f ( t ) = π B 1 [ exp ( j ϕ 1 ) + exp ( - j ϕ 2 ) ] exp ( j ω s t ) ,

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