Abstract

We develop a method for determinating the relative positions of the lidar transmitter (LT) and the local oscillator (LO) frequencies in Doppler CO2 lidars. It uses the weak spectral asymmetry of TEA CO2 laser pulses, defined by a number of secondary peaks at the high-frequency side of the main spectrum peak. Depending on the sign of the beat frequency, these peaks may appear in the demodulated spectrum at either the high- or the low-frequency side. Each laser pulse spectrum is compared with reference spectra with two types of asymmetry, with the cross-correlation coefficients used as criteria. The performance of the method at different values of signal-to-noise ratio is analyzed numerically. The method is also applied to raw data from the lidar reference channel and demonstrates good performance at noise levels lower than the secondary peaks in the pulse spectrum or at a signal-to-noise ratio of ≥20 dB. Application of the pulse spectrum asymmetry for lidar frequency stabilization is analyzed. Lidar operation without frequency stabilization is considered as well. The method offers a simple Doppler lidar hardware for the creation of low-cost coherent lidars, velocimeters–rangefinders, etc.

© 1999 Optical Society of America

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References

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  1. J. W. Bilbro, “Atmospheric lidar Doppler velocimetry: an overview,” Opt. Eng. 19, 533–541 (1980).
    [CrossRef]
  2. R. M. Measures, Laser Remote Sensing: Fundamentals and Applications (Wiley Interscience, New York, 1984).
  3. M. J. Post, “Comparing Doppler lidar and radar for meteorological applications,” presented at the Coherent Laser Radar Meeting, 23–27 June 1997, Linköping, Sweden.
  4. E. W. McCaul, H. B. Bluestein, R. J. Doviak, “Airborne Doppler lidar techniques for observing severe thunderstorms,” Appl. Opt. 25, 698–708 (1986).
    [CrossRef] [PubMed]
  5. M. J. Post, R. E. Cupp, “Optimizing a pulsed Doppler lidar,” Appl. Opt. 28, 4145–4258 (1990).
    [CrossRef]
  6. D. V. Stoyanov, B. M. Bratanov, E. V. Stoykova, “Novel wide-band Doppler lidar detection technique,” Rev. Sci. Instrum. 66, 2400–2404 (1995).
    [CrossRef]
  7. D. V. Stoyanov, V. S. Marinov, B. M. Bratanov, V. N. Naboko, E. V. Stoykova, “Using a novel wideband Doppler detection technique in CO2 Lidars with low frequency laser stability,” in Coherent Laser Radar, Vol. 19 of 1995 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1995) pp. 277–280.
  8. J.-L. Lachambre, P. Lavigne, M. Verreault, G. Otis, “Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2 laser,” IEEE J. Quantum Electron. QE-14, 170–177 (1978).
    [CrossRef]
  9. J. A. Weiss, J. M. Schnur, “Heterodyne detection of frequency sweeping in the output of transverse-excitation CO2 lasers,” Appl. Phys. Lett. 22, 453–454 (1973).
    [CrossRef]
  10. G. Scott, A. L. S. Smith, “Stabilization of single mode TEA laser,” Opt. Commun. 50, 325–329 (1984).
    [CrossRef]
  11. M. Dufour, H. Egger, W. Seelig, “High beam-quality TEA lasers,” Opt. Commun. 19, 334–338 (1976).
    [CrossRef]
  12. V. S. Marinov, D. V. Stoyanov, V. N. Naboko, S. V. Naboko, “Performance of 10.6 µm CO2 Doppler lidar at low laser frequency stability using fixed hard target,” in IXth International School of Quantum Electronics: Lasers—Physics and Applications, P. A. Atanasov, ed., Proc. SPIE3052, 290–295 (1996).

1995 (1)

D. V. Stoyanov, B. M. Bratanov, E. V. Stoykova, “Novel wide-band Doppler lidar detection technique,” Rev. Sci. Instrum. 66, 2400–2404 (1995).
[CrossRef]

1990 (1)

M. J. Post, R. E. Cupp, “Optimizing a pulsed Doppler lidar,” Appl. Opt. 28, 4145–4258 (1990).
[CrossRef]

1986 (1)

1984 (1)

G. Scott, A. L. S. Smith, “Stabilization of single mode TEA laser,” Opt. Commun. 50, 325–329 (1984).
[CrossRef]

1980 (1)

J. W. Bilbro, “Atmospheric lidar Doppler velocimetry: an overview,” Opt. Eng. 19, 533–541 (1980).
[CrossRef]

1978 (1)

J.-L. Lachambre, P. Lavigne, M. Verreault, G. Otis, “Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2 laser,” IEEE J. Quantum Electron. QE-14, 170–177 (1978).
[CrossRef]

1976 (1)

M. Dufour, H. Egger, W. Seelig, “High beam-quality TEA lasers,” Opt. Commun. 19, 334–338 (1976).
[CrossRef]

1973 (1)

J. A. Weiss, J. M. Schnur, “Heterodyne detection of frequency sweeping in the output of transverse-excitation CO2 lasers,” Appl. Phys. Lett. 22, 453–454 (1973).
[CrossRef]

Bilbro, J. W.

J. W. Bilbro, “Atmospheric lidar Doppler velocimetry: an overview,” Opt. Eng. 19, 533–541 (1980).
[CrossRef]

Bluestein, H. B.

Bratanov, B. M.

D. V. Stoyanov, B. M. Bratanov, E. V. Stoykova, “Novel wide-band Doppler lidar detection technique,” Rev. Sci. Instrum. 66, 2400–2404 (1995).
[CrossRef]

D. V. Stoyanov, V. S. Marinov, B. M. Bratanov, V. N. Naboko, E. V. Stoykova, “Using a novel wideband Doppler detection technique in CO2 Lidars with low frequency laser stability,” in Coherent Laser Radar, Vol. 19 of 1995 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1995) pp. 277–280.

Cupp, R. E.

M. J. Post, R. E. Cupp, “Optimizing a pulsed Doppler lidar,” Appl. Opt. 28, 4145–4258 (1990).
[CrossRef]

Doviak, R. J.

Dufour, M.

M. Dufour, H. Egger, W. Seelig, “High beam-quality TEA lasers,” Opt. Commun. 19, 334–338 (1976).
[CrossRef]

Egger, H.

M. Dufour, H. Egger, W. Seelig, “High beam-quality TEA lasers,” Opt. Commun. 19, 334–338 (1976).
[CrossRef]

Lachambre, J.-L.

J.-L. Lachambre, P. Lavigne, M. Verreault, G. Otis, “Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2 laser,” IEEE J. Quantum Electron. QE-14, 170–177 (1978).
[CrossRef]

Lavigne, P.

J.-L. Lachambre, P. Lavigne, M. Verreault, G. Otis, “Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2 laser,” IEEE J. Quantum Electron. QE-14, 170–177 (1978).
[CrossRef]

Marinov, V. S.

D. V. Stoyanov, V. S. Marinov, B. M. Bratanov, V. N. Naboko, E. V. Stoykova, “Using a novel wideband Doppler detection technique in CO2 Lidars with low frequency laser stability,” in Coherent Laser Radar, Vol. 19 of 1995 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1995) pp. 277–280.

V. S. Marinov, D. V. Stoyanov, V. N. Naboko, S. V. Naboko, “Performance of 10.6 µm CO2 Doppler lidar at low laser frequency stability using fixed hard target,” in IXth International School of Quantum Electronics: Lasers—Physics and Applications, P. A. Atanasov, ed., Proc. SPIE3052, 290–295 (1996).

McCaul, E. W.

Measures, R. M.

R. M. Measures, Laser Remote Sensing: Fundamentals and Applications (Wiley Interscience, New York, 1984).

Naboko, S. V.

V. S. Marinov, D. V. Stoyanov, V. N. Naboko, S. V. Naboko, “Performance of 10.6 µm CO2 Doppler lidar at low laser frequency stability using fixed hard target,” in IXth International School of Quantum Electronics: Lasers—Physics and Applications, P. A. Atanasov, ed., Proc. SPIE3052, 290–295 (1996).

Naboko, V. N.

V. S. Marinov, D. V. Stoyanov, V. N. Naboko, S. V. Naboko, “Performance of 10.6 µm CO2 Doppler lidar at low laser frequency stability using fixed hard target,” in IXth International School of Quantum Electronics: Lasers—Physics and Applications, P. A. Atanasov, ed., Proc. SPIE3052, 290–295 (1996).

D. V. Stoyanov, V. S. Marinov, B. M. Bratanov, V. N. Naboko, E. V. Stoykova, “Using a novel wideband Doppler detection technique in CO2 Lidars with low frequency laser stability,” in Coherent Laser Radar, Vol. 19 of 1995 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1995) pp. 277–280.

Otis, G.

J.-L. Lachambre, P. Lavigne, M. Verreault, G. Otis, “Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2 laser,” IEEE J. Quantum Electron. QE-14, 170–177 (1978).
[CrossRef]

Post, M. J.

M. J. Post, R. E. Cupp, “Optimizing a pulsed Doppler lidar,” Appl. Opt. 28, 4145–4258 (1990).
[CrossRef]

M. J. Post, “Comparing Doppler lidar and radar for meteorological applications,” presented at the Coherent Laser Radar Meeting, 23–27 June 1997, Linköping, Sweden.

Schnur, J. M.

J. A. Weiss, J. M. Schnur, “Heterodyne detection of frequency sweeping in the output of transverse-excitation CO2 lasers,” Appl. Phys. Lett. 22, 453–454 (1973).
[CrossRef]

Scott, G.

G. Scott, A. L. S. Smith, “Stabilization of single mode TEA laser,” Opt. Commun. 50, 325–329 (1984).
[CrossRef]

Seelig, W.

M. Dufour, H. Egger, W. Seelig, “High beam-quality TEA lasers,” Opt. Commun. 19, 334–338 (1976).
[CrossRef]

Smith, A. L. S.

G. Scott, A. L. S. Smith, “Stabilization of single mode TEA laser,” Opt. Commun. 50, 325–329 (1984).
[CrossRef]

Stoyanov, D. V.

D. V. Stoyanov, B. M. Bratanov, E. V. Stoykova, “Novel wide-band Doppler lidar detection technique,” Rev. Sci. Instrum. 66, 2400–2404 (1995).
[CrossRef]

V. S. Marinov, D. V. Stoyanov, V. N. Naboko, S. V. Naboko, “Performance of 10.6 µm CO2 Doppler lidar at low laser frequency stability using fixed hard target,” in IXth International School of Quantum Electronics: Lasers—Physics and Applications, P. A. Atanasov, ed., Proc. SPIE3052, 290–295 (1996).

D. V. Stoyanov, V. S. Marinov, B. M. Bratanov, V. N. Naboko, E. V. Stoykova, “Using a novel wideband Doppler detection technique in CO2 Lidars with low frequency laser stability,” in Coherent Laser Radar, Vol. 19 of 1995 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1995) pp. 277–280.

Stoykova, E. V.

D. V. Stoyanov, B. M. Bratanov, E. V. Stoykova, “Novel wide-band Doppler lidar detection technique,” Rev. Sci. Instrum. 66, 2400–2404 (1995).
[CrossRef]

D. V. Stoyanov, V. S. Marinov, B. M. Bratanov, V. N. Naboko, E. V. Stoykova, “Using a novel wideband Doppler detection technique in CO2 Lidars with low frequency laser stability,” in Coherent Laser Radar, Vol. 19 of 1995 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1995) pp. 277–280.

Verreault, M.

J.-L. Lachambre, P. Lavigne, M. Verreault, G. Otis, “Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2 laser,” IEEE J. Quantum Electron. QE-14, 170–177 (1978).
[CrossRef]

Weiss, J. A.

J. A. Weiss, J. M. Schnur, “Heterodyne detection of frequency sweeping in the output of transverse-excitation CO2 lasers,” Appl. Phys. Lett. 22, 453–454 (1973).
[CrossRef]

Appl. Opt. (2)

Appl. Phys. Lett. (1)

J. A. Weiss, J. M. Schnur, “Heterodyne detection of frequency sweeping in the output of transverse-excitation CO2 lasers,” Appl. Phys. Lett. 22, 453–454 (1973).
[CrossRef]

IEEE J. Quantum Electron. (1)

J.-L. Lachambre, P. Lavigne, M. Verreault, G. Otis, “Frequency and amplitude characteristics of a high repetition rate hybrid TEA-CO2 laser,” IEEE J. Quantum Electron. QE-14, 170–177 (1978).
[CrossRef]

Opt. Commun. (2)

G. Scott, A. L. S. Smith, “Stabilization of single mode TEA laser,” Opt. Commun. 50, 325–329 (1984).
[CrossRef]

M. Dufour, H. Egger, W. Seelig, “High beam-quality TEA lasers,” Opt. Commun. 19, 334–338 (1976).
[CrossRef]

Opt. Eng. (1)

J. W. Bilbro, “Atmospheric lidar Doppler velocimetry: an overview,” Opt. Eng. 19, 533–541 (1980).
[CrossRef]

Rev. Sci. Instrum. (1)

D. V. Stoyanov, B. M. Bratanov, E. V. Stoykova, “Novel wide-band Doppler lidar detection technique,” Rev. Sci. Instrum. 66, 2400–2404 (1995).
[CrossRef]

Other (4)

D. V. Stoyanov, V. S. Marinov, B. M. Bratanov, V. N. Naboko, E. V. Stoykova, “Using a novel wideband Doppler detection technique in CO2 Lidars with low frequency laser stability,” in Coherent Laser Radar, Vol. 19 of 1995 OSA Technical Digest Series (Optical Society of America, Washington, D.C., 1995) pp. 277–280.

R. M. Measures, Laser Remote Sensing: Fundamentals and Applications (Wiley Interscience, New York, 1984).

M. J. Post, “Comparing Doppler lidar and radar for meteorological applications,” presented at the Coherent Laser Radar Meeting, 23–27 June 1997, Linköping, Sweden.

V. S. Marinov, D. V. Stoyanov, V. N. Naboko, S. V. Naboko, “Performance of 10.6 µm CO2 Doppler lidar at low laser frequency stability using fixed hard target,” in IXth International School of Quantum Electronics: Lasers—Physics and Applications, P. A. Atanasov, ed., Proc. SPIE3052, 290–295 (1996).

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Figures (9)

Fig. 1
Fig. 1

Power spectra of demodulated TEA CO2 laser pulses (dashed curves) and simulated pulses with chirp rate b = +0.018 MHz/µs2 (solid curves). (a) Positive spectra (f B > 0), (b) negative spectra (f B < 0). f ref < |f B |.

Fig. 2
Fig. 2

Spectral asymmetry orientation of coherently detected and demodulated TEA CO2 laser pulses, depending on the relationship of optical frequencies f LT and f LO. (a) Emitted spectrum for f LT > f LO, (b) demodulated spectrum for f LT > f LO, (c) emitted spectrum for f LT < f LO, (d) demodulated spectrum for f LT < f LO.

Fig. 3
Fig. 3

PDF (filled circles) of Δrr 0 estimates built over 2000 simulated laser shots with positive spectral orientation; SNR’s of (a) 15 and (b) 5 dB. Best Gaussian fits are shown by solid curves.

Fig. 4
Fig. 4

Standard deviation of Δrr 0 estimates as a function of SNR (squares) and percentage of correct Δrr 0 sign estimates (triangles).

Fig. 5
Fig. 5

PDF’s of Δrr 0 estimates built over data from 512 NOAA shots. The best Gaussian fit is shown as a solid curve.

Fig. 6
Fig. 6

Block schematic of the Doppler lidar transmitter with reference channels and frequency-stabilization hardware when the spectral asymmetry of laser pulses is used (some well-known blocks are omitted for simplicity): 2, cw SL; 4, optical mixer for cw radiation; 5, frequency stabilization by the absolute value of the beat frequency f B ; 6 optical mixer for the emitted laser pulse; 7, pulse reference channel for correcting the frequency difference between the emitted pulse and the LO; other blocks as labeled.

Fig. 7
Fig. 7

Tolerable fluctuations Δf of laser transmitter frequency f LT for several Doppler demodulation techniques: (a) complex Doppler demodulator with Δff Dm; (b) performance in two bands about f LO with Δff Dm; (c) wideband Doppler demodulation method6,7; real demodulator with Δff Dm; (d) wideband Doppler demodulator in the two bands about f LO when spectral asymmetry is used as an independent channel.

Fig. 8
Fig. 8

Fluctuations of the absolute value of the intermediate beat frequency (experimental data).

Fig. 9
Fig. 9

Estimates of the PDF of Δrr 0 built over 380 shots of a CO2 Doppler lidar operating at low laser frequency stability (experimental data). The best Gaussian fit is shown by a solid curve.

Equations (7)

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fLTt=fLT0+Δft,
Δft=bt2,
fBt=|fLTt-fLO|=|fB0+Δft|=|fB0|+sgnfB0Δft,
F˜0t=|fBt-fref|=F0+sgnfB0Δft.
r+=maxjk=0N PkPk-j+k=0N Pk2k=0NPk+21/2, r-=maxjk=0N PkPk-j-k=0N Pk2k=0NPk-21/2.
Δr=r+-r-,
sgnfB=sgnΔr.

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