Diffraction grating is an optical element whose properties are periodically modulated in one dimension. Transmissive diffraction gratings consist of many thin lines of either absorptive material or thin grooves, (indentations), on an otherwise transparent substrate. Light transmission through a diffraction grating occurs along discrete directions, called diffraction orders. Here a diode laser beam, (635 nm), is split into many diffraction orders, with the +1 order containing most of the power. This grating groove density is 300 lines/mm.
