The effect of the variation in the area sensitivity upon the calibration of instruments incorporating biplanar vacuum photodiodes for the measurement of laser power and energy is discussed. A technique for the measurement of the area sensitivity is described, and the experimental results for several tubes are given. At the present time it would appear to be difficult to use biplanar vacuum phctodiodes in devices to measure laser energy or power.
R. L. Smith and R. J. Phelan, Jr., "Limitations of the Use of Vacuum Photodiodes in Instruments for the Measurement of Laser Power and Energy," Appl. Opt. 12, 795-798 (1973)