الفهرس 
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Abstract
electrical signal in amperes or volts to the input optical power in watts, quantified as a quotient of the detector output by a monochromatic radiation input at each wavelength. Especially, the Si photodiode is widely used in realizing, disseminating, and comparing the spectral responsivity scale at various national metrology institutes. The spectral irradiance responsivity of a photodetector is considered as the product of the spectral power responsivity in A/W by the area of its precision aperture in cm2.
This work aimed to develop a standardized radiometric setup for realizing the absolute spectral irradiance responsivity in the wavelength range from 500 nm to Absolute Spectral responsivity of photodetectors is a key measurand and a fundamental requirement for the detector-based realization in both photometric, radiometric and colorimetric applications.
Spectral responsivity of an optical detector describes the spectral dependence of its output 950 nm in 10 nm increments at the photometry and radiometry division in the National Institute of Standards (NIS), Egypt. This setup was established with high accurate measurements by using a detector-based method. A silicon trap detector, calibrated against the primary standard cryogenic radiometer, was used as a transfer standard for the calibration of S2281 Hamamatsu silicon photodiode, as a working standard. The measurements were performed using a conventional lamp-monochromator-based comparator setup in the overfilled geometry with the reference Si trap detector using the so-called substitution method.
In our monochromator-based facility, the monochromator was used as a wavelength selector. The emission spectra of calibrated lamp sources was used to obtain wavelength calibration for the double-monochromator in the UV through the visible to the near infrared spectra regions.
For accurate measurement of spectral irradiance responsivity, a complete characterization of the system was done including studies of the long-term stability of the 1 KW-FEL lamp’s output power used as an irradiance source, response linearity of the S2281 Si photodiode, spatial response and irradiance uniformity. The accompanied uncertainty components affecting the measurements were investigated considering all probable sources of errors for each item. This uncertainty budget was studied and discussed through a model based on the Guide to Uncertainty in Measurement (GUM) statistical method.
The S2281 Si photodiode independent irradiance response from 500 nm to 950 nm wavelength range was modelled and described as a modified ideal quantum detector by a few parameters. Therefore, our approach to get a primary realization is to estimate the two loss mechanisms, reflectance and the internal quantum deficiency (IQD), separately using a developed model. The irradiance response model was used to validate our experimental results at the wavelength range of interest. Hence, our lab can establish a standardized radiometric method based on Si-trap detector for measuring spectral irradiance responsivity; this scale has a great importance in several fields such as medical, industrial, astronomy.....etc.
The upgraded method have many applications such as a more precise spectral irradiance or illuminance calibration different light sources, realization of candela, solar irradiance for of outdoor solar cell calibration and spectral calibration of most light sources.