A reference calorimeter for laser energy measurements

Abstract

Principles and detailed procedures are described for measuring la se r energy and power in terms of e lectrica l e ne rgy based on voltage, resistance , and frequency standards. The construction of a sma ll isoperibol ca lorimetcr used for th e measurements is desc ribed. The ca lorimeter wi ll accommoda te 0.0] to 20.1 and 4 X 10 5 to I W cw and is limit ed to a maximum pul se intens it y of 0.1 .I/cm'. The s tandard deviation of comparison meas urements using two calorimeters and a beam s plitter is 0.08 percent when the s maller energy input is not less than 0. 3 1. The estimated limit s of sys temati c eITor for one ca lorim eter are ± 1.0 percent of the laser e ne rgy mea s ured by the calorimeter.Key words: Calorin1Ptry: la se r: lase r calorimetry: lase r energy measurement; lase r power measurement.

Laser power measurement standards: A comparison of two scales

“…3 and 4 show results within the instrument uncertainties. The estimated overall worst-case uncertainty in the value of the correction factor for the test QED 100, at the heliumneon laser wavelength, is ± 0.81 percent for a reverse bias of 9 V and ±0.78 percent for a reverse bias of 18 V. 4 …”

“…1 J/ crrr' for shorter pulses). The C-series calorimeters and the theory of isoperibol calorimetry have been described elsewhere [4], [6]. The Center for Devices and Radiological Health (CDRH) of the Food and Drug Administration (FDA) also maintains a C-series calorimeter.…”

“…A set of reference calorimeters, designated as the C-series, is maintained by the National Bureau of Standards (NBS), Boulder, CO, as the scale for energy measurements of low-power continuous wave (CW) lasers [4], [5].…”

The Absolute Measurement of Radiant Power

“…At about the same time, a different section at the NBS developed instruments for the accurate maintenance of the NBS scale of laser power and laser energy (West et al, 1972). A new comparison between Geist's (1971) absolute thermopile and West et al's (1972) C-series calorimeter gave agreement to 0.09% .…”

Quality assurance program for the NBS C, K, and Q laser calibration systems

“…(2) A calorimeter window may get slightly dirty due to the vacuum system or some other source and needs to be cleaned. (3) A fingerprint on the beamsplitter will give an inaccurate ratio and require cleaning. (4) Reversing the direction a laser beam passes through a sapphire beamsplitter may give a different beamsplitter ratio.…”