Antonio Corróns

New model for the internal quantum efficiency of photodiodes based on photocurrent analysis

A new expression for the internal quantum efficiency of a photodiode is presented. It is obtained from the analysis of the photocurrent generated within the diode, considering the power and the cross-sectional diameter of the incident beam. The model explains variations of the internal quantum efficiency with irradiance that are not explained by other existing models, although this experimental fact was already known. The well-known phenomenon of supraresponsivity is also explained with this model. Finally, we show the dependence of the internal quantum efficiency on the variables involved in the model.

Principal components analysis on the spectral bidirectional reflectance distribution function of ceramic colour standards

The Bidirectional Reflectance Distribution Function (BRDF) is essential to characterize an objects reflectance properties. This function depends both on the various illumination-observation geometries as well as on the wavelength. As a result, the comprehensive interpretation of the data becomes rather complex. In this work we assess the use of the multivariable analysis technique of Principal Components Analysis (PCA) applied to the experimental BRDF data of a ceramic colour standard. It will be shown that the result may be linked to the various reflection processes occurring on the surface, assuming that the incoming spectral distribution is affected by each one of these processes in a specific manner. Moreover, this procedure facilitates the task of interpolating a series of BRDF measurements obtained for a particular sample.

Absolute spectral irradiance scale in the 700–2400 nm spectral range

An absolute spectral irradiance scale for the 700-2400 nm range has been developed. The scale is based on an absolute radiometer and a series of interference filters, which were used to determine the spectral irradiance of quartz halogen incandescent lamps at a number of discrete wavelengths. Values at intermediate wavelengths have been obtained by interpolation. This new scale was compared with NIST standards based on blackbody radiance. Both scales were found to agree within +/- 1%.

Spectral responsivity uncertainty of silicon photodiodes due to calibration spectral bandwidth

A systematic study on the uncertainty in spectral responsivity of silicon photodiodes due to the calibration spectral bandwidth is presented. Two of the most common types of silicon photodiodes in the field of optical power measurements have been used in this work: one with thickness of about 100 nm of SiO2 and the other with thickness about 27 nm of SiO2 .I t is shown that the spectral responsivity error will be negligible (5 × 10 −4 ) using a spectral bandwidth up to 20 nm in the calibration if the effective wavelength of the spectral transfer function, including the distribution of the radiation source, is calculated and the measured responsivity is assigned to that effective wavelength. In other cases, the error depends not only on the extent of the interval isolated by the spectral analysis system but also on the shape of the spectral isolation function.

Response uniformity of silicon photodiodes

The response uniformity of four silicon photodiodes, previously calibrated by using the self-calibration technique, has been measured. The response nonuniformity over the sensitive surface is not a negligible source of uncertainty in this case.

Key Comparison EUROMET.PR-K3.b.1: Bilateral comparison on illuminance responsivity between IFA-CSIC/Spain and UME/Turkey

A bilateral comparison of illuminance responsivity scales between the UME and the IFA-CSIC was carried out, where the IFA-CSIC acted as the pilot and link to the key comparison CCPR-K3.b. The ratio of the measured illuminance responsivities (UME/IFA) was 1.0003 with expanded uncertainty of 0.0084 (k = 2) including the uncertainty of the comparison and the uncertainties of the realization of the scales. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCPR, according to the provisions of the Mutual Recognition Arrangement (MRA).

Reference-frequency generation by Raman-enhanced four-photon mixing

Reference-frequency generation for optical fiber instrumentation is now restricted to the frequency bands in which the reference materials have well-resolved absorption lines. We study analytically and experimentally the possibility of generating reference wavelengths by use of Raman-enhanced four-photon mixing in an optical fiber. We show that it is possible to generate efficiently frequencies that are 10-40 nm away from the absorption bands of the usual reference materials: acetylene (12C2H2), hydrogen cyanide (HCN), and similar or derived species. As a demonstration we use an acetylene cell to generate reference frequencies that cover the whole C (1530-1565 nm) and some part of the L (1565-1625 nm) transmission bands of the optical fiber.

Measurement of standard aluminium mirrors, reflectance versus light polarization

The dependence of the reflectance of standard aluminium mirrors on the polarization status of the incident light has been calculated and measured for an angle of incidence close to normal , so that the systematic uncertainty introduced by not controlling the light polarization status in spectrophotometric measurements of specular reflectance can be known and then eliminated or minimized.

Realization of an infrared spectroradiometer

This paper describes a fully automatic spectroradiometer designed to measure the absolute spectral irradiance of light sources in the 800-2400-nm spectral range by direct comparison of radiation sources with a standard source, both placed the same distance away. The total estimated uncertainty in the comparison process is <1%, which, added to the standard source uncertainty, allows us to obtain the absolute spectral irradiance values of sources in this spectral range with an accuracy of better than 3%.

Germanium photodiodes calibration as standards of optical fiber systems power measurements

The absolute spectral responsivity, the linearity, the response uniformity across the sensitive surface, and the angular response are the main radiometric characteristics of any detector measuring optical power. These characteristics have been determined for two Ge photodiodes at the wavelengths of 1300 and 1550 nm. The measurement techniques used, the results and their uncertainties are presented. Based on them, the measurement conditions that have to be met to perform accurate measurements of the power leaving a fiber are established.