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Funding Information: The authors of PTB are grateful to Ingmar Müller who designed, set up and characterized the PQEDs calibrated by PTB and to Uwe Johannsen who set up and improved the cryogenic radiometer calibration facility of PTB. The research leading to these results has received funding from the European Community’s Seventh Framework Programme, ERA-NET Plus, under Grant Agreement No. 217257, from the European Metrology Research Programme (EMRP) Project SIB57 ‘New Primary Standards and Traceability for Radiometry’ and from the project 18SIB10 chipS.CALe (EMPIR). The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. The EMPIR programme is co-financed by the Participating States and from the European Union’s Horizon 2020 research and innovation programme. EI acknowledges the support by the Academy of Finland Flagship Programme, Photonics Research and Innovation (PREIN), decision number: 320167. Publisher Copyright: © 2022 BIPM & IOP Publishing Ltd. The stability of induced junction silicon photodiodes used to construct the predictable quantum efficient detector (PQED) has been studied over a time period of a decade by measurements of its spectral responsivity against absolute cryogenic radiometers (CR) in two independent laboratories at CMI and PTB. PQEDs operated at room temperature show a long-term temporal stability within 150 ppm over a broad spectral range during a 10-year period, well within the range of the claimed measurement uncertainty values of the CRs. This long term stability fulfills one of the fundamental requirements to establish a new primary standard for the measurement of power of optical radiation.

We report the characterisation and calibration of a new laser pulse energy measurement device, developed for pico-joule pulse energy measurement at repetition rates up to 1 kHz. The device comprises a charge integration amplifier operating in conjunction with an input charge source; a light trapping photo-detector, which converts an incident laser pulse to a charge pulse. The novel amplifier individually integrates each charge pulse from the source and outputs a corresponding 20-bit resolution digital signal. This signal is converted to pulse energy through post processing, knowing the absolute responsivity of the photodiode detector and the calibration factors of the charge amplifier. A differential evolution algorithm is used to determine optimised values for the feedback capacitors of the amplifier, the amplifier gain and offset. The values measured by the new laser pulse energy meter were compared with those obtained from measurements traceable to both the high and low-level laser pulse energy scales maintained by NIST, Boulder. These were consistent within the combined expanded measurement uncertainty. This new device offers lower uncertainty and portability, suitable for field use.

This paper presents the experimental characterization of predictable quantum efficient detectors, which have been designed for use at room temperature. The aim of the characterization was to validate modelled properties experimentally and, thus, the feasibility of such room temperature predictable quantum efficient detectors to be used as primary radiometric standards for applications in the fields of photometry and radiometry with an aimed uncertainty level of 0.01%. The characterizations were focused on linearity, thermal, angular, spectral and polarization dependencies of the detector that need to be known and considered in the respective applications. The results of the characterization measurements confirm the predictability of the detector, within the aimed 0.01% uncertainty level and, thus, the high potential for using that kind of devices as primary standards for applications in radiometry and photometry.

We present a predictable single-photon source (SPS) based on a silicon vacancy centre in nanodiamond which is optically excited by a pulsed laser. At an excitation rate of 70 MHz the source delivers a photon flux large enough to be measured by a low optical flux detector (LOFD). The directly measured photon flux constitutes an absolute reference. By changing the repetition rate of the pulsed laser, we are able to change the photon flux of our SPS in a controllable way which in turn can act as a reference. The advantage of our method is that it does not require precise knowledge of the source efficiency, but the source is calibrated by the LOFD and can be used for detector responsivity characterizations at the few-photon level.

A comparison down to sub-100-fW optical power level was carried out between a low-noise Silicon photodiode and a low optical flux measurement facility based on a double attenuator technique. The comparison was carried out via a silicon single-photon avalanche diode (Si-SPAD), which acted as transfer standard. The measurements were performed at a wavelength of 770 nm using an attenuated laser as a radiation source at optical power levels between approximately 86 fW and approximately 1325 fW, corresponding to approximately 330 000 photons s−1 and approximately 5.2 × 106 photons s−1, respectively. The mean relative deviation of the detection efficiencies of the Si-SPAD, determined by the Si-photodiode and the low optical flux measurement facility, i.e. between two completely independent traceability routes, was < 0.2%, thus well within the combined standard uncertainty of the two measurements. To our knowledge, this is the first comparison for the detection efficiency of a single photon detector using a direct optical flux measurement by a conventional Si-photodiode at such low power levels.

18 pags., 15 figs., 1 tab., Large-effect pigments, due to their strongly specular reflectance, produce a special visual texture known as sparkle. The use of these pigments in many industries (automotive, cosmetic, paper, architecture...) makes the control of this visual texture necessary. Sparkle measurands have been defined in this article, so that traceability of sparkle measurements can be provided by national metrology institutes or designated institutes. Some of them (Physikalisch-Technische Bundesanstalt, Eidgenössisches Institut für Metrologie, Cesky Metrologicky Institut and Consejo Superior de Investigaciones Científicas) have tested their existing measurement capabilities for the defined sparkle measurands, and their results are presented and thoroughly compared. Two possible sources of systematic error have been identified: inadequate illumination and collection solid angles, and an inadequate size of the virtual aperture used to assess the luminous flux reflected by the effect pigments. Finally, it has been shown that the measures correlate excellently with the sparkle visual data. The results shown in this research support the sparkle measurands defined here as adequate quantities for defining the standard measurement scale of sparkle claimed by industry., This article was written within the EMPIR 16NRM08 Project ‘Bidirectional reflectance definition’ (BiRD). The EMPIR is jointly funded by the participating countries within EURAMET and the European Union. Some of the authors (Instituto de Optica ‘Daza de Valdes’) are also grateful to Comunidad de Madrid for funding the project S2018/NMT4326-SINFOTON2-C.

The solar ultraviolet spectrum captured by commercially available diode-array spectroradiometers is dominated by stray light from longer wavelengths with higher intensity. The implementation of a digital micromirror device in an array spectroradiometer has the potential to enable the precise selection of desired wavelengths as well as the ability to reduce spectral intensity of some wavelengths via selective mirror modulation, both reducing long wavelength stray light. A prototype consisting of off-the-shelf components has been assembled to verify the validity of the base concept, and initial measurements have been performed to confirm the throughput and image qualities such as spectral resolution and astigmatism.

The ?Metrology for Industrial Quantum Communication Technologies? project (MIQC) is a metrology framework that fosters development and market take-up of quantum communication technologies and is aimed at achieving maximum impact for the European industry in this area.MIQC is focused on quantum key distribution (QKD) technologies, the most advanced quantum-based technology towards practical application. QKD is a way of sending cryptographic keys with absolute security. It does this by exploiting the ability to encode in a photon's degree of freedom specific quantum states that are noticeably disturbed if an eavesdropper trying to decode it is present in the communication channel. The MIQC project has started the development of independent measurement standards and definitions for the optical components of QKD system, since one of the perceived barriers to QKD market success is the lack of standardization and quality assurance.

The predictable quantum efficient detector (PQED) is intended to become a new primary standard for radiant power measurements in the wavelength range from 400 nm to 800 nm. Characterization results of custom-made single induced junction photodiodes as they are used in the PQED and of assembled PQEDs are presented. The single photodiodes were tested in terms of linearity and spatial uniformity of the spectral responsivity. The highly uniform photodiodes were proved to be linear over seven orders of magnitude, i.e. in the radiant power range from 100 pW to 400 µW. The assembled PQED has been compared with a cryogenic electrical substitution radiometer with a very low uncertainty of the order of 30 ppm. Experimental results show good agreement with the modelled response of the PQED to optical radiation and prove a near unity external quantum efficiency.

We present the results and discussion of two methods for achieving a higher degree of wavelength accuracy of double grating monochromators. In particular, we assessed the benefits of using differential evolution curve fitting techniques to minimize wavelength uncertainties associated with the manufacture of lead screws in sine-bar driven monochromators. Absolute wavelength-scale uncertainties better than ?0.1?nm can be realized using this technique.We also report the realization of an accurate and repeatable wavelength scale, using a novel calibration technique, that is applicable to a wide range of monochromators. We present results demonstrating the robustness of the technique by realizing an absolute wavelength scale, across four grating sets from 250?nm to 1600?nm, with scale uncertainties within ?0.02?nm and repeatable to ?0.005?nm.