Abstract

Ultraviolet radiation, in a band of wavelengths near 300 nm, produced by the flashlamps used to pump the ruby rod, is responsible for nearly all the photochemical decomposition (irreversible bleaching) of methanolic solutions of cryptocyanine used as passive shutters (Q-switches) in high-peak-power ruby lasers. The laser beam itself has little or no irreversible effect upon cryptocyanine.

© 1972 Optical Society of America

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References

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  1. R. A. Jeffreys, Ind. Chim. Belg, Suppl. 2, 495 (1959).
  2. B. H. Soffer, J. Appl. Phys. 35, 2551 (1964).
    [CrossRef]
  3. Private communication to one of us (J. D. M.) during the Fifth International Congress on Quantum Electronics (1969).
  4. R. M. Brown, R. J. Stone, Appl. Opt. 8, 2356 (1969).
    [CrossRef]
  5. B. L. Booth, Appl. Opt. 8, 2559 (1969).
    [CrossRef] [PubMed]
  6. Absorbanceis the logarithm to the base 10 of the reciprocal of the transmittance. It is to be distinguished from absorbtance, the fraction of the incident beam absorbed by the sample.
  7. It is likely that most of the temperature rise was actually produced by the conduction of heat from the air forced through the laser head to cool the ruby rod and flashlamps, the temperature of which is elevated above that of the room by the blower motor. This suggests even more strongly that ir radiation plays no more than a trivial part in the photochemical decomposition of the dye.

1969 (2)

1964 (1)

B. H. Soffer, J. Appl. Phys. 35, 2551 (1964).
[CrossRef]

1959 (1)

R. A. Jeffreys, Ind. Chim. Belg, Suppl. 2, 495 (1959).

Booth, B. L.

Brown, R. M.

Jeffreys, R. A.

R. A. Jeffreys, Ind. Chim. Belg, Suppl. 2, 495 (1959).

Soffer, B. H.

B. H. Soffer, J. Appl. Phys. 35, 2551 (1964).
[CrossRef]

Stone, R. J.

Appl. Opt. (2)

Ind. Chim. Belg, Suppl. (1)

R. A. Jeffreys, Ind. Chim. Belg, Suppl. 2, 495 (1959).

J. Appl. Phys. (1)

B. H. Soffer, J. Appl. Phys. 35, 2551 (1964).
[CrossRef]

Other (3)

Private communication to one of us (J. D. M.) during the Fifth International Congress on Quantum Electronics (1969).

Absorbanceis the logarithm to the base 10 of the reciprocal of the transmittance. It is to be distinguished from absorbtance, the fraction of the incident beam absorbed by the sample.

It is likely that most of the temperature rise was actually produced by the conduction of heat from the air forced through the laser head to cool the ruby rod and flashlamps, the temperature of which is elevated above that of the room by the blower motor. This suggests even more strongly that ir radiation plays no more than a trivial part in the photochemical decomposition of the dye.

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Figures (4)

Fig. 1
Fig. 1

Dependence of the absorbance of a methanolic solution of cryptocyanine (~10−6 M) upon the number of prior exposures of that solution to the light from laser flashlamps. The electrical energy discharged through the lamps during each exposure was 2020 J; the laser itself was prevented from firing by covering one of the cavity end mirrors with a black cloth. Triangles represent a run of exposures made with a glass plate between the flashlamps and the quartz cell containing the dye solution. Circles represent a run of exposures made without the glass plate. The lines are best fit to the points in the least-squares sense. Absorbances were measured after each exposure at a wavelength of 706 nm.

Fig. 2
Fig. 2

Dependence of the rate of decrease in absorbance per exposure upon the amount of energy discharged through the flashlamps during the exposure. The mean decrease in absorbance (of 706 nm light by methanolic solutions of cryptocyanine) per exposure (to flashlamp light) during a run of several exposures was measured first with the laser pevented from firing [both with (square) and without (circles) shielding the sample by means of a glass plate during the run], and then with the laser firing [both with (diamond) and without (triangles) shielding]. The line is least-squares-best-fit to the circles. Error bars, representing 68% confidence limits, are based only on the statistical uncertainty in the rate of decrease in absorbance during a run and do not reflect variations in experimental conditions from one run to the next.

Fig. 3
Fig. 3

Dependence of the decrease in absorbance upon the amount of energy in the laser output. Each point represents a single exposure of a methanolic solution of cryptocyanine to both the light from the flashlamps and the spontaneous and stimulated emission from the ruby rod. The energy discharged through the flashlamps during the exposures was 1600 J (circles), 2020 J (triangles), or 2500 J (squares). Vertical error bars represent the estimated accuracy of a single measurement of absorbance at a wavelength of 706 nm; horizontal error bars represent the combined effects of the inaccuracy of the optical calorimeter (given by the manufacturer) and the uncertainty in extrapolating the energy readings from the cooling curves produced by the calorimeter.

Fig. 4
Fig. 4

Dependence of the decrease in absorbance at 706 nm upon the wavelength of the arc lamp light to which the sample had been exposed previously. Circles represent measurement made on 3–4 August 1971 and triangles, on 31 August–7 September 1971. The measured decreases in the absorbance have been normalized to account for the variation in the intensity of the arc lamp with wavelength. The solid line represents the absorption spectrum of a typical sample for purposes of com parison with the decomposition data. Experimental details and a discussion of errors are given in the text.

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