Abstract

A new type of spectrometer, with no movable parts, no optical sources, and no precision engineering, is demonstrated by the use of computer interpretation of interference patterns. Currently it has a resolution sufficient to determine the optical spectrum of a two-moded distributed-feedback laser with 2-nm mode spacing. The spectrometer operates by transmitting the laser light through two pinholes to generate an interference pattern in the far field. The interference pattern is captured with an infrared camera and is transferred to a computer. The spectrum of the light is extracted from this interference pattern by the maximum-entropy method of spectral estimation.

© 1995 Optical Society of America

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References

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  1. J. P. Burg, in Proceedings of 37th Meeting of the Society of Exploration Geophysicists (Society of Exploration Geophysicists, Tulsa, Okla., 1967), p. 375 (also reprinted in Ref. 2).
  2. D. G. Childers, Modern Spectrum Analysis (Institute of Electrical and Electronics Engineers, New York, 1978), p. 17.
  3. S. M. Kay, S. L. Marple, Proc. IEEE 69, 1380 (1981).
    [CrossRef]
  4. G. F. Engen, IEEE Trans. Microwave Theory Tech. MTT-25, 1070 (1977).

1981 (1)

S. M. Kay, S. L. Marple, Proc. IEEE 69, 1380 (1981).
[CrossRef]

1977 (1)

G. F. Engen, IEEE Trans. Microwave Theory Tech. MTT-25, 1070 (1977).

Burg, J. P.

J. P. Burg, in Proceedings of 37th Meeting of the Society of Exploration Geophysicists (Society of Exploration Geophysicists, Tulsa, Okla., 1967), p. 375 (also reprinted in Ref. 2).

Childers, D. G.

D. G. Childers, Modern Spectrum Analysis (Institute of Electrical and Electronics Engineers, New York, 1978), p. 17.

Engen, G. F.

G. F. Engen, IEEE Trans. Microwave Theory Tech. MTT-25, 1070 (1977).

Kay, S. M.

S. M. Kay, S. L. Marple, Proc. IEEE 69, 1380 (1981).
[CrossRef]

Marple, S. L.

S. M. Kay, S. L. Marple, Proc. IEEE 69, 1380 (1981).
[CrossRef]

IEEE Trans. Microwave Theory Tech. (1)

G. F. Engen, IEEE Trans. Microwave Theory Tech. MTT-25, 1070 (1977).

Proc. IEEE (1)

S. M. Kay, S. L. Marple, Proc. IEEE 69, 1380 (1981).
[CrossRef]

Other (2)

J. P. Burg, in Proceedings of 37th Meeting of the Society of Exploration Geophysicists (Society of Exploration Geophysicists, Tulsa, Okla., 1967), p. 375 (also reprinted in Ref. 2).

D. G. Childers, Modern Spectrum Analysis (Institute of Electrical and Electronics Engineers, New York, 1978), p. 17.

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Figures (4)

Fig. 1
Fig. 1

Diffraction pattern, whose brightness is proportional to E(t)2 + E(t + τ)2 + 2E(t)E(t + τ), which is essentially a measure of the optical signal’s autocorrelation 〈E(t)E(t + τ)〉, with the delay τ a function of the distance x.

Fig. 2
Fig. 2

Experimental arrangement used to capture the field autocorrelation onto a computer. LD1, LD2, laser diodes.

Fig. 3
Fig. 3

Comparison of the maximum-entropy method (solid curve), the fast-Fourier-transform method (dotted curve), and the commercial spectrum analyzer (inset) spectra for a test signal consisting of the superposition of two single-mode distributed-feedback laser diode signals, 12.9 nm apart.

Fig. 4
Fig. 4

Maximum-entropy method and commercial spectrum analyzer trace (inset) for a test signal made up of one single-mode and one double-moded distributed-feedback laser.

Equations (2)

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P ( ω ) = - C ( τ ) exp ( - i ω τ ) d τ .
P ( ω ) = S ( ω ) = [ | - C ( τ ) exp ( - i ω τ ) d τ | 2 ] 1 / 2 .

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