Diffraction grating

Introduction :
In optics, a diffraction grating is an optical part with a periodic structure, which splits and diffraction light into some beams travelling in different directions. The directions of these beams depend on the spacing of the grating and the wavelength of the brightness so that the grading acts as dispersive element. Because of this, diffraction gradings are generally used in monochromators and spectrometers.

Diffraction grating definition

A photographic slide with a well model of black lines forms a simple grating. For useful applications, diffraction gradings usually have grooves or rulings on their outside rather than dark lines. Such gradings can be moreover transparent or reflective. Gratings which change the phase rather than amplitude of the incident light are also formed, frequently using holography.
                                            (Source : Wikipedia)

Theory of operation

The connection between the grading spacing and the angles of the event and diffracted beams of light is known as the grating equation. According to the Huygens–Fresnel standard, each point on the wave front of a propagating signal can be measured to act as a point source, and the wave front at any following point can be found by calculation together the contributions from every of these individual position sources.
                                                              (Source :Wikipedia)
An idealized diffraction grating is measured here which is made up of a position of long and considerably narrow slits of spacing d. When a level surface signal of wavelength λ is incidence usually on the grating, each slit in the grading acts as a point source propagate in all directions. The light in a exacting direction, θ, is made up of the interfering components from each slit.This occurs at angles θ_m which satisfy the connection dsinθ_m/λ=|m| where d is the division of the slits and m is a digit. Thus, the diffracted light will have maxima at angles θ_m given by

It is basic to show that if a plane wave is event at an angle θ_i, the grating equation becomes

Gratings can be made in which a mixture of the incident light are modulate in a regular example

• Transparency (transmission amplitude gratings)
• Reflectance (reflection amplitude gratings)

• Refractive index (phase gratings)
• Direction of optical axis (optical axis gratings)

The grating equation applies in all these cases.a


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