Establishing a new ultraviolet and near-infrared spectral responsivity scale

A new primary spectral responsivity scale has been established in the ultra violet (UV) and near-infrared (NIR) spectral regions (200 nm to 400 nm and 0.9 mu m to 2.5 mu m) at an uncertainty level of less than 0.5% (2 sigma) o ver most of this range. The new scale is maintained on solid-state transfer standard detectors which were calibrated traceable to the NPL cryogenic ra diometer via spectrally flat pyroelectric detectors using monochromatic rad iation from both laser and monochromator sources. The UV scale was establis hed on GaAsP detectors while the NIR scale is based on InGaAs (0.9 mu m to 1.64 mu m) and modified InSb/sphere detectors (1 mu m to 2.5 mu m). This pa per discusses the choice of the new transfer standard detectors, describes how the new scale was established, and analyses the component uncertainties which contribute to the total uncertainty associated with the new scale.