Satisfactory role of LEDs as a light receiving component and their uses in science demonstration experiments for educational purposes

摘要

Light emitting diodes (LEDs) can be used also as a light-receiving element which is less likely to be saturated than photodiodes. The author has actually employed LEDs for the purpose of receiving optical signals in a science demonstration experiment set of optical communication for educational purposes in various ages. In some cases, LEDs as a light-receiving element can realize better quality of reproduced sounds transmitted in the demonstration experiment set via optical transmission, as compared to the case where a normal photodiode is employed as a light-receiving element. Furthermore, by using LEDs both for a light source and a light-receiving component, relationships among color of light (wavelengths or frequencies) and their energies as well as bandgap energies of semiconductor materials can be explained in such demonstration. In this paper, some exemplary data of output voltage characteristics obtained from an LED employed as a light-receiving element, as well as typical demonstration sets for educational purposes, are explained.