[Laser] grating?

[J. Forster]

> Zack wrote:

> I don't know if you got your questions answered.  A diffraction grating is a
> material with very fine grooves cut in it very close together (on the order of
> microns), or any pattern of alternating clear and dark lines.

There are reflection and transmission gratings. Clear and black are the
transmission type. Reflection type are made either photographically or by ruling
a series of very fine lines on a reflective surface, aluminum on glass, for
example. They are typically 150 to 2400 grooves/mm.

Gratings are used for applications such as monochromators (tunable optical band
pass filters) and wavelength division multiplexers / demultiplexers.. Basically,
they use the wave properties of light,  and constructive and destructive
interference, to deflect an  incident light beam through an angle which is
dependant on the wavelength of the light.

John