| 单词 | diffraction grating |
| 释义 | diffraction grating An optical device comprising a set of fine parallel slits or grooves etched onto a material in order to product interference patterns that separate components of a spectrum of incoming light. The fundamental principle is that different wavelengths diffract to different extents, so they can be separated much as a prism separates a composite polychromatic incident light beam into its constituent wavelengths of light. Human beings see this as the separation of white light into a rainbow of colored light. There are two types of diffraction gratings: • A transmission grating comprises grooves etched into a transparent material such as glass. As the elements of light in the incident spectrum strike the grooves at a certain angle, they are diffracted and, therefore, separated to various degrees, with blue light diffracted the least and red light the most.This approach is used effectively in fiber optics transmission systems (FOTS) employing wavelength division multiplexing (WDM). • A reflection grating comprises grooves ruled into a surface that can be either plane or concave. In a distributed feedback laser (DFB laser), a diffraction grating with a concave surface serves to focus light without affecting the spectra.This approach is much more effective than the mirror technique employed with a Fabry-Perot laser and vertical cavity surface-emitting laser (VCSEL). See also DFB laser, diffraction, Fabry-Perot laser, FOTS, laser, VCSEL, and WDM. |
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