High-accuracy optical power measurements by using electrical-substitution cryogenic radiometer

Abstract

An optical power scale is established at Ulusal Metroloji Enstitü sü (UME) using the helium-cooled primary-level electricalsubstitution cryogenic radiometer. The scale is established at discrete laser wavelengths of vertically polarized tuneable Ar ϩ , 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 Ϫ4 . 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.

The inclusion of source effect consideration in irradiance determination

“…The detailed descriptions of these measurements are given in our previous work [10]. Following the optical power measurements responsivities of optical detection element of filter radiometer were determined by measuring its current response to the measured optical power.…”

New traceability chains in the photometric and radiometric measurements at the National Metrology Institute of Turkey

“…Intensity stabilized and vertically polarized lasers (He-Ne, Ar + and Nd:YAG) are used for the realization of the scale [5,6]. Lasers are placed on computer-controlled and motorized linear translation stage, which enables each laser beam to send into the measurement setup sequentially.…”

“…Lasers are placed on computer-controlled and motorized linear translation stage, which enables each laser beam to send into the measurement setup sequentially. The output power of each laser then stabilized by using an electro-optics modulator technique [5]. A spatial filter is used to produce a clean Gaussian laser beam with a desired dimension.…”

“…The measurement of optical power at each laser wavelength is performed using static substitution method [5]. By comparing the temperature rise induced in the radiometer cavity by the incident optical radiation with that obtained by electrical heating in turn several times for each power, optical power is calculated according to Eq.…”

Filter-radiometer-based realization of candela and establishment of photometric scale at UME

“…The absolute responsivity of filter-radiometer was linked to the absolute optical power measurements, which is based on helium-cooled electrical-substitution cryogenic radiometer [14]. Optical power measurements were performed at discrete laser wavelengths of vertically polarized tuneable Ar+ (488.0 and 514.5 nm wavelengths) and fixed Nd: YAG (532.0 nm wavelength) and He-Ne (632.8 nm wavelength) laser sources (beam diameters were aligned to $2 mm).…”