Traceable laser power measurements of diode laser radiation in the near infrared

Abstract

We report a new calibration setup for laser radiometry at the Physikalisch-Technische Bundesanstalt, the German National Metrology Institute. Measurements of laser diode power of free beam diode lasers in the near infrared spectral range at a wavelength of 808 nm for powers up to 250 W and at wavelengths of 915 nm, 940 nm, and 980 nm for laser powers up to 25 W have been established. The calibration setup, the standard detector, the uncertainty budget and first calibration results will be presented and discussed. The standard uncertainty of the HLR302 standard detector is 0.2%. This uncertainty might be the main contribution to the overall uncertainty in customer calibrations, depending on the quality of the transfer detectors.

Revisiting the limits of photon momentum based optical power measurement method, employing the case of multi-reflected laser beam

“…Optical transmition = Power N+1 Power = Power output Power input (10) Using the values of the force measurements plugging in equation (8), which is the equations ( 1) and ( 5) solved for optical power, the magnitude of the input optical power can be calculated. In figure 9, we show the results of this calculation normalized against the actual input optical power, which was measured using the reference optical monitor detector (refer schematics in figure 6).…”

“…For thermal detectors, the optical power is determined by measuring the relative change of the passively dissipated heat resulting from the absorbed energy of the optical field. Traditionally, flat or cavity-based thermal detectors are used as reference standards, which are directly traceable to electrical SI units (volt, ohm), or indirectly, through a primary standard for low optical power (cryogenic radiometer) [8][9][10]. Although the existing reference standard thermal detectors achieve relative expanded measurement uncertainties of approximately 0.2% (k = 2) [11] for optical power measurements, for example at 1 W, this values increase up to 1%-2% for power measurements in the kW range, additionally becoming a nontrivial technological task to implement because their measurement capability and accuracy strongly depend on the absorbance and heat capacity of the cavity used as a sensor.…”

Multi-kilowatt cw laser power measurement comparison between national standards

“…However, currently these modifications are not utilized, and the EC-PM is calibrated optically through laser power using a transfer standard power meter. This calibration by transfer standard is one of the steps [10,11] that make up the traceability chain (figure 2) leading to the primary standard-the PTB cryogenic radiometer [12]. The SI-traceability for the cryogenic radiometer is through the volt and ohm.…”

Flowing-water optical power meter for primary-standard, multi-kilowatt laser power measurements

“…High-power (multi-kilowatt) continuous wave (CW) lasers have been in use since the 1970s and now are finding numerous applications due to a combination of the increased availability, reliability and cost effectiveness of multi-kilowatt solid-state laser technologies as well as their increased use in manufacturing, defense and research. Characterizing these lasers can be challenging, particularly for accurate measurement of laser power [1]. The obvious difficulty is in making an accurate measurement of the energy deposition rate of laser light when that power is capable of melting, cutting or otherwise altering most material put in front of it.…”