The basic characteristics of the grating
There are four main grating basic properties: dispersion, beam, polarization and phase matching, most applications are based on the four grating characteristics.
Dispersive grating refers to a raster can be the same at different wavelengths of incident light diffraction conditions to a different direction, which is the most well-known nature of the grating, which makes grating spectrometer replace the prism become the core element. Dispersion properties of the grating by a grating equation can be derived out, the problem will be analyzed in more detail later, is derived generalized grating dispersion formula.
Splitting grating Grating means capable of directing a monochromatic light into a plurality of incident light beams emitted ability. Bright interconnect applications, optical coupling, uniform illumination, optical communications, optical computing. Evaluation of the performance indicators are: diffraction efficiency, splitting ratio, compression ratio, non-uniformity, and the spot light spot mode. At present, more commonly used grating beam splitter has: Dammann grating beam splitter, Tablot grating beam splitter, kinoform grating beam splitter, a waveguide grating beam splitter and the like. In addition, phase Fresnel lens array beam splitter, Gbaor lens beam splitter and other lens-type beam splitter is quite common.
In the range of the scalar field, the polarization characteristics of the grating is often ignored, and therefore, the polarizing grating was not widely known before. But the theory and experiments have proved that a well-designed, produced excellent grating can be used to make a polarizer, 1/2 wave plate, 1/4-wave plate and a phase compensation and so on. Polarization characteristics grating need a vector theory analysis grating can get, we will be in a later section of the polarization properties of grating theoretical analysis. The nature of the phase matching grating having a grating refers to the ability of two different wave propagation constant curse put together. The most obvious example is a waveguide grating coupler disaster, it will be a bunch of free-space propagation beam disaster is bonded to the optical waveguide.
According to the Rayleigh wave vector expansion, a bunch of plane wave illumination on the grating will produce an infinite number of plane wave diffraction, the distance between adjacent diffracted wave of wave vector along the x direction between the projection is a constant equal to the grating, namely ixkk-i2 / T0 = plane electromagnetic wave can be seen as a model in the passive, homogeneous medium, and therefore have the ability to grating wave vector along a fixed direction projection grating wave vector difference integral multiple of different plane waves are coupled.