Özcan Bazkir Ulusal Metroloji Enstitütsü (Turkey) Sevilay Ugur Ulusal Metroloji Enstitusu (Turkey) Farhad Samedov TUBITAK National Metrology Institute (Turkey) Akif Esendemir Middle East Technical Univ. (Turkey)
An optical power scale is established at Ulusal Metroloji Enstitüsü (UME) using the helium-cooled primary-level electrical-substitution cryogenic radiometer. The scale is established at discrete laser wavelengths of vertically polarized tuneable Ar+, fixed He-Ne, and Nd:YAG (with second harmonic) laser sources. To increase measurement accuracy, laser intensities are stabilized to better than 0.009% using an electro-optical modulator. The spatial profiles of polarized laser beams are cleaned with a spatial filter. The optical power is measured using the static substitution method with an uncertainty of a few parts in 10–4. Repeatability of optical power measurements in the static substitution method, the measurement of window transmittance, and the measurement of power in a scattered beam are the most significant uncertainty components.