title: A recording sampling system for measuring laser energy.
abstract: An apparatus has been designed and built which simultaneously measures the energy incident on a biological system which is being exposed to a laser beam. The advantages of the direct reading system are: (1) no attention is required of the laser operator, (2) a permanent record is produced, (3) true integration of the pulse train is accomplished, (4) high inherent accuracy, (5) in conjunction with a fast oscilloscope, it reproduces pulse waveforms with minimum distortion, and (6) calibration is simple and direct. Basically the system employs a fast high-current capability photodiode, a high-quality integrating capacitor, an emission-limited pump diode with a servo-motor amplifier combination for dark current balance. The photodiode cathode surface is S-1 so that both ruby and neodymium wavelengths 694.3 mmicro and 1060 mmicro, respectively, may be measured. Reproducibility is better than 3% when compared with a blackbody receiver (cone radiometer). A Tektronix 585A oscilloscope and P-80 cathode follower probe fitted with a 50-Omega load resistor can be plugged into the photodiode housing in place of the integrating capacitor for waveform observation and power-level measurements. Calibration on an absolute basis is easily accomplished by simultaneous comparison with a calibrated blackbody receiver (cone radiometer).
authors.affiliation: Department of Biophysics, MedicalCollege of Virginia, Richmond, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Williams
authors.forename: H A
authors.initials: HA
authors.lastname: Mueller