A high-accuracy cryogenic radiometer has been developed at the National Institute of Standards and Technology to serve as a primary standard for optical power measurements. This instrument is an electrical-substitution radiometer that can be operated at cryogenic temperatures to achieve a relative standard uncertainty of 0.021% at an optical power level of 0.8 mW. The construction and operation of the high-accuracy cryogenic radiometer and the uncertainties in optical power measurements are detailed.

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National Institute of Standards and Technology high-accuracy cryogenic radiometer

The photon energy dependence of the mean energy W required to produce an electron-hole pair in silicon for photons with energies between 50 and 1500 eV was determined from the spectral responsivity of selected silicon photodiodes. The spectral responsivity was measured with a relative uncertainty of less than 0.3% using monochromatized synchrotron radiation whose radiant power was measured with a cryogenic electrical substitution radiometer. In order to deduce W from the spectral responsivity of photodiodes with a relative uncertainty of about 1%, a method for the calculation of photon and electron escape losses from silicon photodiodes was developed and the model for the charge carrier recombination losses was improved. In contrast to recent theoretical and experimental results, a constant value W=(3.66±0.03) eV was obtained in the photon energy range from 50 to 1500 eV. The present experimental results are confirmed by calculation of the pair creation energy in silicon from data from the literature for ...

http://www.ba.infn.it/~mazziot/JAP02926.pdf

Mean energy required to produce an electron-hole pair in silicon for photons of energies between 50 and 1500 eV

Using the National Institute of Standards and Technology high-accuracy cryogenic radiometer (HACR), we have realized a scale of absolute spectral response between 406 and 920 nm The HACR, an electrical-substitution radiometer operating at cryogenic temperatures, achieves a combined relative standard uncertainty of 0021% Silicon photodiode light-trapping detectors were calibrated against the HACR with a typical relative standard uncertainty of 003% at nine laser wavelengths between 406 and 920 nm Modeling of the quantum efficiency of these detectors yields their responsivity throughout this range with comparable accuracy

Realization of a scale of absolute spectral response using the National Institute of Standards and Technology high-accuracy cryogenic radiometer

The Physikalisch-Technische Bundesanstalt has further improved and extended its spectral responsivity scale based on the laser-operated radiation thermometry cryogenic radiometer. Five laser wavelengths in the ultraviolet (UV) (238 nm to 400 nm) and another fifteen in the visible and near-infrared (NIR) (400 nm to 1015 nm) almost cover the entire spectral range where silicon photodiodes can be used in air. The lasers employed are a Kr+ laser, an Ar+ laser with optional intra-cavity frequency-doubling, and a continuously tuneable Ti:sapphire ring laser. The total relative standard uncertainty of the spectral responsivity at the laser lines is u = 10-4 in the visible and NIR below 950 nm and u = 10-3 in the UV. With an improved model for interpolation between the laser wavelengths, a continuous scale of spectral responsivity has been established in the wavelength range 400 nm to 1015 nm.

https://iopscience.iop.org/article/10.1088/0026-1394/37/4/3/pdf

Accurate determination of the spectral responsivity of silicon trap detectors between 238 nm and 1015 nm using a laser-based cryogenic radiometer

The accuracy of detector calibration in the UV, vacuum-ultraviolet, and soft-x-ray spectral ranges could be significantly improved by the use of the synchrotron radiation electrical substitution radiometer (SYRES) as the primary detector standard. The SYRES radiometer is optimized for use with spectrally dispersed synchrotron radiation as supplied by two monochromator beam lines in the radiometry laboratory of the Physikalisch-Technische Bundesanstalt at the Berlin electron-storage ring (BESSY). Wavelength ranges from 0.8 to 25 nm and from 35 to 400 nm are covered. The typically available radiant power of approximately 1-10 microW can be measured with the SYRES radiometer with a standard relative uncertainty of less than 0.2%. The spectral responsivity of qualified photodiodes for use as secondary detector standards is determined by direct comparison with the primary detector standard at an arbitrary wavelength. At present, the scale of spectral responsivity is realized with a standard relative uncertainty of well below 1% in the spectral ranges 0.8-3.5 nm, 5-25 nm, and 120-400 nm. We provide a comprehensive description of the SYRES radiometer and of the two facilities for detector calibration in the UV and vacuum-ultraviolet spectral ranges and in the soft-x-ray spectral range, respectively, and we discuss the achievable uncertainties in the calibration of detectors.

Synchrotron-radiation-operated cryogenic electrical-substitution radiometer as the high-accuracy primary detector standard in the ultraviolet, vacuum-ultraviolet, and soft-x-ray spectral ranges.

Different types of photodiode have been characterized with respect to uniformity, linearity, stability of responsivity and temperature coefficient at several wavelengths between 257 nm and 799 nm based on cryogenic radiometry and intensity stabilized lasers. The Hamamatsu S1337 photodiode was found to be the best suited for use as a high accuracy transfer standard for both the visible and UV spectral regions. For low-level radiant power measurement, this kind of photodiode can be calibrated via a cryogenic radiometer with a total uncertainty as low as ±0,02% in the visible and ±0,25% in the UV.

https://iopscience.iop.org/article/10.1088/0026-1394/30/4/015/pdf

Characterization of Photodiodes in the UV and Visible Spectral Region Based on Cryogenic Radiometry

A novelty C+L single-mode fiber (CL fiber for short) which can expand L-band communication is proposed to meet the urgent demand of optical fiber transmission bandwidth for large capacity communication system. The influence of L-band attenuation on the optical signal-to-noise ratio (OSNR) of the system is analyzed and calculated; through the simulation of dense wavelength division multiplexing (DWDM) system, the requirements for fiber attenuation warping degree (FAWD) of CL fiber in 100Gbit/s rate DWDM system are obtained; and the CL fiber and its main attenuation parameters are defined. The results show that, the OSNR of L-band for conventional single-mode fiber will be 2dB-2.5dB worse than traditional C-band on 100km span system, so it is very important to limit the FAWD of L-band; if the L-band transmission can meet the link requirements in relevant standards, it is recommended that the FAWD Δα1625 of CL fiber is suitable to be controlled below 0.015dB/km, and the fiber attenuation warping degree difference (FAWDD) Δα is suitable to be controlled below 0.005dB/km.

Fu Lei

Papers

Characterization of Photodiodes in the UV and Visible Spectral Region Based on Cryogenic Radiometry

Numerical Simulation of C+L Broadband Single-mode Fiber