Abstract

In this research directed toward using lidar methods for mapping concentrations of a variety of hazardous gases and vapors in an indoor workplace, a need was identified for a CO2 laser that would meet certain special requirements, including an ability to produce 50–100-ns FWHM pulses in pulse pairs having interpulse spacings of 5–100 μs with each pulse of the pair being independently wavelength selectable. A laser was constructed with a low-pressure CO2 amplifier section because of CO2's long upper lasing level lifetime (>60 μs). This permitted the Q switching of two output pulses from a single laser amplifier electrical transverse discharge pulse, while allowing several microseconds for wavelength changing between pulses. An intra-cavity beam telescope was employed to use the amplifier discharge cavity cross section efficiently with the small CdTe Q-switch crystals available. A 1200-Hz oscillating grating with a high-resolution grating position sensor was used to change and reprogram wavelengths rapidly. Programming of wavelengths was accomplished by selecting appropriate delay times from the grating position reference signal for triggering the laser amplifier and the Q switch. Most of the basic performance goals of the device were achieved in the laboratory prototype.

© 1991 Optical Society of America

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References

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  1. F. R. Faxvog, H. W. Mocker, “Rapidly Tunable CO2-TEA Laser,” Appl. Opt. 21, 3986–3987 (1982).
    [CrossRef] [PubMed]
  2. J. Fox, J. Ahl, “High Speed Tuning Mechanism for CO2 Lidar Systems,” Appl. Opt. 25, 3830–3834 (1986).
    [CrossRef] [PubMed]
  3. J. Fox, J. Ahl, “Tuning Device for CO2 Hetrodyne Detection Lidar,” Rev. Sci. Instrum. 60, 1258–1261 (1989).
    [CrossRef]
  4. A. Crocker, R. M. Jenkins, M. Johnson, “A Frequency Agile, Sealed-Off CO2 TEA Laser,” J. Phys. E 18, 133–135 (1985).
    [CrossRef]
  5. A. Siegman, Lasers (University Science, Mill Valley, Calif.1986).
  6. A. Yariv, Quantum Electronics (Wiley, New York, 1975).
  7. D. A. Eastham, Atomic Physics of Lasers (Taylor & Francis, London, 1986).
  8. C. S. Willett, Introduction to Gas Lasers: Population Inversion Mechanism (Pergamon, New York, 1974).
  9. Lasers and Optronics, 1989 Buying Guide (Gordon, Dover, N.J., 1989), pp. 164–180.
  10. H. V. Piltingsrud, “Tunable CO2 laser-based photo-optical systems for surveillance of indoor workplace pollutants,” in Proceedings of the Second International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals (Environmental Protection Agency, Washington, D.C., to be published).

1989 (1)

J. Fox, J. Ahl, “Tuning Device for CO2 Hetrodyne Detection Lidar,” Rev. Sci. Instrum. 60, 1258–1261 (1989).
[CrossRef]

1986 (1)

1985 (1)

A. Crocker, R. M. Jenkins, M. Johnson, “A Frequency Agile, Sealed-Off CO2 TEA Laser,” J. Phys. E 18, 133–135 (1985).
[CrossRef]

1982 (1)

Ahl, J.

J. Fox, J. Ahl, “Tuning Device for CO2 Hetrodyne Detection Lidar,” Rev. Sci. Instrum. 60, 1258–1261 (1989).
[CrossRef]

J. Fox, J. Ahl, “High Speed Tuning Mechanism for CO2 Lidar Systems,” Appl. Opt. 25, 3830–3834 (1986).
[CrossRef] [PubMed]

Crocker, A.

A. Crocker, R. M. Jenkins, M. Johnson, “A Frequency Agile, Sealed-Off CO2 TEA Laser,” J. Phys. E 18, 133–135 (1985).
[CrossRef]

Eastham, D. A.

D. A. Eastham, Atomic Physics of Lasers (Taylor & Francis, London, 1986).

Faxvog, F. R.

Fox, J.

J. Fox, J. Ahl, “Tuning Device for CO2 Hetrodyne Detection Lidar,” Rev. Sci. Instrum. 60, 1258–1261 (1989).
[CrossRef]

J. Fox, J. Ahl, “High Speed Tuning Mechanism for CO2 Lidar Systems,” Appl. Opt. 25, 3830–3834 (1986).
[CrossRef] [PubMed]

Jenkins, R. M.

A. Crocker, R. M. Jenkins, M. Johnson, “A Frequency Agile, Sealed-Off CO2 TEA Laser,” J. Phys. E 18, 133–135 (1985).
[CrossRef]

Johnson, M.

A. Crocker, R. M. Jenkins, M. Johnson, “A Frequency Agile, Sealed-Off CO2 TEA Laser,” J. Phys. E 18, 133–135 (1985).
[CrossRef]

Mocker, H. W.

Piltingsrud, H. V.

H. V. Piltingsrud, “Tunable CO2 laser-based photo-optical systems for surveillance of indoor workplace pollutants,” in Proceedings of the Second International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals (Environmental Protection Agency, Washington, D.C., to be published).

Siegman, A.

A. Siegman, Lasers (University Science, Mill Valley, Calif.1986).

Willett, C. S.

C. S. Willett, Introduction to Gas Lasers: Population Inversion Mechanism (Pergamon, New York, 1974).

Yariv, A.

A. Yariv, Quantum Electronics (Wiley, New York, 1975).

Appl. Opt. (2)

J. Phys. E (1)

A. Crocker, R. M. Jenkins, M. Johnson, “A Frequency Agile, Sealed-Off CO2 TEA Laser,” J. Phys. E 18, 133–135 (1985).
[CrossRef]

Rev. Sci. Instrum. (1)

J. Fox, J. Ahl, “Tuning Device for CO2 Hetrodyne Detection Lidar,” Rev. Sci. Instrum. 60, 1258–1261 (1989).
[CrossRef]

Other (6)

A. Siegman, Lasers (University Science, Mill Valley, Calif.1986).

A. Yariv, Quantum Electronics (Wiley, New York, 1975).

D. A. Eastham, Atomic Physics of Lasers (Taylor & Francis, London, 1986).

C. S. Willett, Introduction to Gas Lasers: Population Inversion Mechanism (Pergamon, New York, 1974).

Lasers and Optronics, 1989 Buying Guide (Gordon, Dover, N.J., 1989), pp. 164–180.

H. V. Piltingsrud, “Tunable CO2 laser-based photo-optical systems for surveillance of indoor workplace pollutants,” in Proceedings of the Second International Symposium on Field Screening Methods for Hazardous Wastes and Toxic Chemicals (Environmental Protection Agency, Washington, D.C., to be published).

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Figures (17)

Fig. 1
Fig. 1

Q-switched double-pulse CO2 laser.

Fig. 2
Fig. 2

CO2 laser timing diagram.

Fig. 3
Fig. 3

Grating position sensing circuit.

Fig. 4
Fig. 4

Q-switch electrical pulse generator.

Fig. 5
Fig. 5

Grating position sensor pulses b–d timing jitter for 120-s measurement.

Fig. 6
Fig. 6

Q-switch long-pulse.

Fig. 7
Fig. 7

Electrical pulse on a Q-switch crystal.

Fig. 8
Fig. 8

Q-switched laser output pulse (∼60 ns FWHM).

Fig. 9
Fig. 9

Q-switched laser output pulse (∼100 ns FWHM).

Fig. 10
Fig. 10

Laser amplifier transverse electrical discharge pulse current.

Fig. 11
Fig. 11

Pulse energy versus pressure and delay time.

Fig. 12
Fig. 12

Effect of delay T7T1 on ratio of output pulse energies.

Fig. 13
Fig. 13

Effect of Q-switch pulse width on ratio of first to second laser output-pulse energies.

Fig. 14
Fig. 14

Change in output-pulse width with Q-switch pulse width.

Fig. 15
Fig. 15

Tuning of 10P20 emission line.

Fig. 16
Fig. 16

Tuning of 9P14 emission line.

Fig. 17
Fig. 17

Laser output-pulse energies.

Equations (1)

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n ( t ) = n i e exp ( r 1 ) t / τ c ,

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