For many experiments, it is important to know the exact wavelength of the source of light. Unfortunately, wavelengths of lasers or light-emitting diodes are subject to change depending on the environment factors such as ambient temperature. Those changes that can be as significant as a fraction of a nanometer are important for exploring the structural positions of ions in metals. Today, equipment is calibrated using emission spectrum analysis (spectrophotometric method) but this is a difficult process, however, requiring long-term stable temperature of the light source.
Scientists at the Institute of Semiconductor Physics, Siberian Branch of the Russian Academy of Sciences have suggested a principally new and simpler method of measuring emission wavelength which allows to detect changes of up to 10−3 nanometer.
Ellipsometer is an optical device commonly used to identify the properties of a substance. During a regular procedure, polarised light with a known wavelength is emitted through the sample in order to determine its properties based on the nature of the phase shift. The Novosibirsk-based researchers suggested using the ellipsometer to address an opposite task: to let a ray of light through a substance with known properties in order to calculate the light wavelength using the phase shift.
Preliminary calibration of the device allows to determine the phase shift for any light wavelength. When the measurements are done, the researchers can calculate the light source wavelength knowing the phase shift. In the course of the experiment, the emission of one and the same laser was studied at 22 C° and 32 C°. It was discovered that in the former example it generates light with the wavelength of 660.0 nanometer, and in the latter case the wavelength is 660.6 nanometer. Such minute change can insignificantly distort the results of some physical experiments. The researchers believe that the method will meet a high demand as convenient and miniature ellipsometer already exist.
Further information: D. V. Marin, V. N. Fedorinin, Tokhir Khasanov, “Measuring the Wavelength of Light Sources Using Ellipsometer Method.” the Scientific Instrument Engineering, vol. 21, March 2011.
Dmitrij Tsendin published by STRF.ru