To measure a photodiode reflectance, the reference detector is placed first at position A and its reading is recorded. Afterward the photodiode to be tested is introduced in the laser beam at half way between the shutter and position A, with an angle of incidence about 3º and the reference photodiode is moved to position B and its response recorded. Then the reflectance is given by the ratio between the reference detector reading at position B and the reading at position A. Placing the photodiode to be tested a that position assures that the beam seen by the reference detector runs the same distance in both cases, avoiding errors associated to the divergence of the laser beam. A 3º incidence angle is small enough so that the measured reflectance is considered as the normal incidence reflectance. Finally, just to remark that the reference detector is placed at normal incidence any time.By this method the spectral reflectance of one set of photodiodes from the same manufacturer and batch and another set of three photodiodes (from the same manufacturer) used to maintain the spectral responsivity scale at the Institute for Applied Physics (CSIC) has been measured at wavelengths: 441.8 nm (He-Cd), 568.2 nm (Kr), 632.8 nm (He-Ne) and 647.1 nm (Kr). A typical uncertainty value for this kind of measurement in this laboratory is 0.15 %, which is determined mainly by the measurement repeatability and the linearity of the reference detector and its associated electronics. Just for identification purposes, the model of all photodiodes studied is S1337-1010BQ. In this work we present the analysis spectral reflectance of silicon photodiodes.

6 páginas, 5 figuras.-- Trabajo presentado al 1st International Congress on Instrumentation and Applied Sciences celebrado en Cancún (México) del 26 al 29 de octubre de 2010.

Peer reviewed