Abstract
The Primary Optical Watt Radiometer (POWR) [1] at NIST realizes and maintains the unit of optical power (watt). POWR is an absolute cryogenic radiometer which uses the principle of electrical substitution to obtain the total power of input optical radiation. It serves as the basis for many radiometric and photometric units and scales realized at NIST, providing optical power measurements with uncertainties as low as 0.02% (k = 1) for continuous wave laser inputs. Currently, a continuously tunable and computer controlled supercontinuum light source is routinely utilized for efficient data collection between 500 nm and 1700 nm (5 nm step size), and a system with a Ti:Sapphire laser/ harmonic generation can produce specific wavelengths in the ultraviolet regime. These measurements are then used to calibrate the optical power responsivity of photodetectors (e.g. Si and InGaAs photodiodes) which serve as standards at NIST and beyond. This talk will introduce electrical substitution and absolute cryogenic radiometers and discuss the role POWR plays in the optical power calibration chain. Case data and lessons learned will be presented for the diverse radiation sources (ultraviolet to near infrared) available for use with POWR. Research in the POWR lab aims to lower the uncertainties in optical power measurements and calibrations whilst streamlining the data collection; future improvements to further this goal will be discussed and include incorporating a closed-cycle cryostat and continuous and automated wavelength coverage between 190 nm and 2300 nm.
1. J. M. Houston and J. P. Rice 2006 Metrologia 43 S31 DOI: 10.1088/0026-1394/43/2/S07
Optical Power Scale Realization at NIST Using the Primary Optical Watt Radiometer (POWR)
The Primary Optical Watt Radiometer (POWR) [1] at NIST realizes and maintains the unit of optical power (watt). POWR is an absolute cryogenic radiometer which uses the principle of electrical substitution to obtain the total power of input optical radiation. It serves as the basis for many radiometric and photometric units and scales realized at NIST, providing optical power measurements with uncertainties as low as 0.02% (k = 1) for continuous wave laser inputs. Currently, a continuously tunable and computer controlled supercontinuum light source is routinely utilized for efficient data collection between 500 nm and 1700 nm (5 nm step size), and a system with a Ti:Sapphire laser/ harmonic generation can produce specific wavelengths in the ultraviolet regime. These measurements are then used to calibrate the optical power responsivity of photodetectors (e.g. Si and InGaAs photodiodes) which serve as standards at NIST and beyond. This talk will introduce electrical substitution and absolute cryogenic radiometers and discuss the role POWR plays in the optical power calibration chain. Case data and lessons learned will be presented for the diverse radiation sources (ultraviolet to near infrared) available for use with POWR. Research in the POWR lab aims to lower the uncertainties in optical power measurements and calibrations whilst streamlining the data collection; future improvements to further this goal will be discussed and include incorporating a closed-cycle cryostat and continuous and automated wavelength coverage between 190 nm and 2300 nm.
1. J. M. Houston and J. P. Rice 2006 Metrologia 43 S31 DOI: 10.1088/0026-1394/43/2/S07