Abstract

A silicon-target vidicon and minicomputer system providing rapid recording, readout, and processing of laser beam intensity profiles is described. Results are presented for 150-psec, 1064-nm neodymium laser pulses. Use of a thick, neutron-transmutation-doped silicon target reduced spatial sensitivity nonuniformities and coherent interference modulation. Modifications of commercial cameras to provide linearized output and timing control are described. The vidicon signal is recorded in a video disk recorder, digitized, and stored on a magnetic disk. Selected 1-D profiles and color isointensity whole beam profiles are available on CRT displays. Using a PDP-11 computer, the beam is analyzed to yield a peak energy flux within 100 sec after the laser pulse. The performance of the vidicon system is compared with photographic film techniques. Results show a sensitivity uniformity of ≥93% peak to peak over a target distance of 9.6 mm, linear dynamic range of ≳20, and absolute flux agreement within ±10%. The system is useful for other laser wavelengths and pulse durations as well as for nonlaser applications.

© 1978 Optical Society of America

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References

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  1. D. Milam, Proc. Soc. Photo-Opt. Instrum. Eng. Eng. (1978, in press).
  2. Research and applications were discussed at the recent International Conference on Neutron Transmutation Doping of Semiconductors at the University of Missouri, Columbia, Missouri (April1978).
  3. E. Savoy, Radio Corporation of America, Lancaster, Pennsylvania; private communication.
  4. P. Capper, J. G. Wilkes, Appl. Phys. Lett. 32, 187 (1978).
    [CrossRef]
  5. J. R. Greenwood, M. C. Zarnstorf, Lawrence Livermore Laboratory; unpublished.

1978 (1)

P. Capper, J. G. Wilkes, Appl. Phys. Lett. 32, 187 (1978).
[CrossRef]

Capper, P.

P. Capper, J. G. Wilkes, Appl. Phys. Lett. 32, 187 (1978).
[CrossRef]

Greenwood, J. R.

J. R. Greenwood, M. C. Zarnstorf, Lawrence Livermore Laboratory; unpublished.

Milam, D.

D. Milam, Proc. Soc. Photo-Opt. Instrum. Eng. Eng. (1978, in press).

Savoy, E.

E. Savoy, Radio Corporation of America, Lancaster, Pennsylvania; private communication.

Wilkes, J. G.

P. Capper, J. G. Wilkes, Appl. Phys. Lett. 32, 187 (1978).
[CrossRef]

Zarnstorf, M. C.

J. R. Greenwood, M. C. Zarnstorf, Lawrence Livermore Laboratory; unpublished.

Appl. Phys. Lett. (1)

P. Capper, J. G. Wilkes, Appl. Phys. Lett. 32, 187 (1978).
[CrossRef]

Other (4)

J. R. Greenwood, M. C. Zarnstorf, Lawrence Livermore Laboratory; unpublished.

D. Milam, Proc. Soc. Photo-Opt. Instrum. Eng. Eng. (1978, in press).

Research and applications were discussed at the recent International Conference on Neutron Transmutation Doping of Semiconductors at the University of Missouri, Columbia, Missouri (April1978).

E. Savoy, Radio Corporation of America, Lancaster, Pennsylvania; private communication.

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Figures (9)

Fig. 1
Fig. 1

Photographic film technique1 for characterization of laser pulse energy profile. The film is exposed by a series of replicas of the laser pulse. A microdensitometer rasters each film exposure to produce an optical density map. From the peak optical density (OD) of each exposure and the relative energies of the replicas, a Hurter-Driffield exposure curve is constructed and used to convert the OD map into a map of relative energy per unit area. The spatial integration of this map is then correlated with the measured laser pulse energy to convert the map into absolute units. The peak flux of the laser pulse is obtained from the normalized map.

Fig. 2
Fig. 2

Schematic diagram of the vidicon–computer based laser data acquisition and analysis system. The components and operation are described in the text.

Fig. 3
Fig. 3

Timing sequence for laser pulse recording. An electrical pulse is sent to the vidicon cameras 33 msec before the laser begins its firing operation. The vidicon electron beam completes the scanning of its present frame and is then blanked for the following frame during which the laser pulse illuminates the vidicon. The laser energy profile is read from the vidicon target in the first field of the next frame and recorded on a magnetic disk.

Fig. 4
Fig. 4

Schematic diagram of the asynchronous–synchronous trigger circuit used to blank the vidicon electron beam for one frame. The video camera circuitry was interrupted at point A, and the modification circuitry was inserted between A and B. The flip–flop is clocked by the synchronous first-field index pulses obtained from a National Semiconductor MM5321 IC in the video camera sync circuitry. Upon receival of the camera arm pulse, the next first-field pulse occurs after the laser pulse is detected; it triggers the video recorder and reenables the e-beam.

Fig. 5
Fig. 5

Illustration of sensitivity variations observed in the response of a conventional Si target vidicon tube to uniform illumination with near-ir light. The origins of the spatial nonuniformity evident in (a) and (b) are discussed in the text.

Fig. 6
Fig. 6

Spatial sensitivity uniformity of the C23250-NTD tube. The 2-D surface (a) illustrates the uniformity of response to a near-ir plane wave incident on the vidicon target. Illumination conditions were the same as used for Fig. 5. In (b), the center video line is plotted above a zero-signal reference line. Spatial resolution in these graphs is ~80 μm; the large scale nonuniformity does not exceed 7%.

Fig. 7
Fig. 7

Dependence of video output signal on the intensity of faceplate illumination. The range of linearity from the unity SN point to full tube output is 100.

Fig. 8
Fig. 8

Comparison of the 1-D laser intensity profiles recorded by the vidicon system (solid lines) and by photographic film (dashed lines). The vertical scales indicate the flux for each pulse.

Fig. 9
Fig. 9

Comparison of peak laser fluxes measured with the vidicon system and with photographic film. The solid line indicates the locus of perfect agreement between the two methods; the dashed lines indicate ±5% deviation from perfect agreement. The maximum in-tersystem disagreement in these data is 10%.

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