Abstract: The facility for automated spectroradiometric calibrations (FASCAL) is the primary facility for calibration of spectral irradiance and spectral radiance at NIST and has been in continuous use since the early 1970s. Due to the increasing demands for spectroradiometric calibration, especially for supporting the monitoring of global environmental changes, a new facility, FASCAL 2, dedicated to calibrating spectral irradiance has been built. This facility will enable faster responses to calibration requests and, ultimately, result in lower uncertainties in the disseminated spectral irradiances. The FASCAL 2 facility is designed with the objective of achieving a signal-to-noise ratio exceeding 1000 : 1 from 250 nm to 2500 nm in a bandwidth of 4 nm to 8 nm when measuring a 1000 W FEL lamp at a distance of 50 cm with a receiving aperture of 1 cm2. The facility will also be capable of calibrating deuterium lamps from 200 nm to 400 nm. The facility has six independent source stations, with four of the stations dedicated to measurements with spectral irradiance lamps and two stations reserved for the realization of spectral irradiance scales and checking the accuracy of automated wavelength. After verifying that the calibrations of spectral irradiance performed in FASCAL and FASCAL 2 agree within their combined uncertainties, FASCAL 2 will become the primary NIST facility for calibration of spectral irradiance.
H W Yoon, J E Proctor and C E Gibson

Abstract: Here we report on an alternative approach for making spectral irradiance measurements of radiation sources traceable, employing our monochromator-based absolute cryogenic radiometer (ACR) facility to its full extent. The method makes use of the continuously tunable absolute radiant flux emerging from the ACR facility to characterize and calibrate the spectral irradiance responsivity of a second adjacent double-monochromator system. This system will be part of a new facility at NMi-VSL, called SIR, that will be used to measure spectral irradiance distributions of radiation sources from the ultraviolet to the far infrared. Following this traceability route, a fully characterized high-temperature Planckian radiator is not needed. Proof-of-principle measurements in the visible part of the spectrum show very encouraging results. Although the new facility is under construction, the theoretical background and a schematic description will be presented in this paper.
E W M van der Ham, H C D Bos and C A Schrama

Abstract: The Measurement Standards Laboratory (MSL) is New Zealand’s national metrology institute and is operated by Industrial Research Ltd (IRL). As such, it ensures that traceable measurements and calibrations are available for all users of measurements in New Zealand. This paper outlines how MSL realises and maintains its radiometric scales, and how these scales are traceably disseminated. The paper describes the development of MSL’s scale of detector spectral responsivity from the ultraviolet to the near infrared and its maintenance on, and dissemination from, novel 5-element silicon photodiode trap detectors. Emphasis is given to the improvements made in the scale of spectral irradiance, the accuracy of which has improved in the ultraviolet region from 6 % to the current 2.3 %
Kathryn Nield, Antoine Bittar, and John Hamlin

Abstract: We present results of measurements obtained with a new monochromator-based cryogenic radiometer facility at NMi/VSL. General design considerations of the facility and associated transfer detectors are discussed. At present, Si detectors can be calibrated between 330 nm and 1200 nm at power levels ranging from 5 µW to 80 µW. A vacuum trap detector of the reflective type has been constructed, which accepts an optical beam in conjunction with spot sizes up to 5 mm in diameter. To check the performance of the system, the trap detector has been calibrated directly against the cryogenic radiometer using lasers at 488.0 nm, 543.4 nm and 632.8 nm and subsequently using the monochromator at the same wavelengths. The agreement is better than 0.02 %
C A Schrama, R Bosma, K Gibb, H Reijn and P Bloembergen

Abstract: By time resolved fluorescence spectroscopy in the psec range the fluorescence behavior of flavines as important endogenous fluorophores was investigated. The substances were examined under various conditions (e.g. pure solutions and cellular suspensions; different buffer systems and pH values). Particular attention was dedicated to the properties of these coenzymes under in situ conditions. The results were applied to test numerical methods for characterization of complex mixtures of fluorophores and for discrimination of different states of flavines.
M. Rübhausenb , M.V. Kleina, D. Budelmannb, B. Schulzb, P. Guptasarmac, M.S. Williamsenc, R. Liangd, D.A. Bonnd and W.N. Hardyd; Journal of Physics and Wolfgang Hoehne, Werner Schramm, Mathias Nittka, Heinz D. Kronfeldt

Abstract: Excitonic processes in the band edge regime determine the optical properties of II–VI bulk and novel epitaxial materials. The interdependences of excitonic systems (i.e. free and bound excitons), high-density systems (e.g. biexcitons) and the transition into the electron-hole plasma state are of high complexity and depend sensitively on sample quality and purity, dopant concentration, excitation condition and density, etc. Resonant excitation spectroscopy and time-resolved analysis of creation and decay processes provide valuable experimental access to clarification of the above-mentioned mutual interactions. In this paper recent results obtained using these methods are surveyed.
In the first part the development of luminescence and resonant excitation of bound exciton systems is treated under various excitation densities, for high excitation levels accompanied by biexciton formation and exciton–exciton collision processes. The specific properties observable when using heteroepitaxial structures instead of conventional bulk samples are discussed.
In the second part the time characteristics of excitonic transitions are evaluated for various impurities, dopants and dopant concentrations, excitation via particular resonant excitation channels, and various excitation densities. Relaxation and conversion channels between excitonic systems are analysed, in particular in strained heteroepitaxial systems which show splitting effects of the bands from which the carriers stem. Time-resolved analysis is demonstrated to be extremely helpful for the analysis of unknown excitonic systems and transitions. Methods of varying the characteristic time constants are discussed, in particular with regard to intentional changes in impurity contents and excitation densities which are interesting for any application.
Gutowski andA. Hoffmann