Absolute reference calorimeter for measuring high power laser pulses

Abstract

A calorimeter for making absolute energy measurements of high power laser pulses is described. The calorimeter, based on volume absorption in a solid, is calibrated electrically and requires no window or vacuum environment. An error analysis is included giving the systematic and random errors of the instrument for a laser measurement. Briefly, the following performance is typical of the 32-mm x 32-mm aperture calorimeter: range 0.4-15-J; random error +/-0.2% (one standard deviation); systematic error +/-2.3%; and an upper operational limit of 3 J/cm(2). Most of the volume absorber documentation is applicable for 1.06 microm; however, the calorimeter should be useful from the near ir through the visible. Absorbers for use with CO(2) lasers in the 9-11-microm range are also discussed.

Calibration service for laser power and energy at 248 nm

“…The geometry of the cavity allows a negligible amount of incident radiation to scatter out. This same geometry was used on the Q-series calorimeters, and measurements on that device confirmed this conclusion [2]. Schott Glass UGl 1 filter glass was employed as the volume absorber [9].…”

“…Previous NIST research in laser calorimetry yielded the development of instruments capable of measuring absolute total energy of pulsed radiation from Nd:YAG lasers operating at 1064 nm [2].…”

“…The total uncertainty is determined by combining the Type A and Type B standard deviations in quadrature and multiplying this result by a factor of 2. The expanded uncertainty, U, is then u \ (2) The values used to calculate the expanded uncertainty are listed in Table II. The number of decimal places used in reporting the mean value of the calibration factors listed in Table I were determined by expressing the total expanded uncertainty to two significant digits.…”

“…NIST measurement of laser energy at the excimer wavelength of 248 nm is accomplished using a pulsed-laser calorimeter. Reference standard calorimeters (QUV-1 and QUV-2) were designed and constructed at NIST to measure the total energy injected during a prescribed period of time [1] [2].…”

Measurement assurance programs

“…Diagrams showing the construction details of the calorimeters can be found in the articles in the Bibliography (e.g., items [39][40][41].…”