VIS Reflective Holographic Gratings

VIS Reflective Holographic Gratings

Holographic Diffraction Gratings are widely applied in stray-light-sensitive scenarios. They are fabricated by exposing a photoresist-coated polished substrate to the standing wave interference fringe field formed by two intersecting laser beams, which forms evenly spaced parallel interference fringes with sinusoidal intensity distribution. Subsequent processing creates linear grating structures with sinusoidal cross-sections.

The solubility of the photoresist material varies with incident light intensity, enabling precise patterning. A reflective film can be coated on the substrate, and grating replication can be realized via the same manufacturing procedure as original ruled gratings.

Featuring fully consistent groove profiles and uniform groove spacing, holographic gratings are free from periodic and random spacing errors, thus eliminating ghost lines and inherent stray light of ruled gratings and achieving remarkably lower stray light levels. They can be manufactured with a groove density up to 3600 grooves per millimeter to acquire higher theoretical resolving power. Minor superficial defects that do not affect optical performance are acceptable for qualified products.

Precautions

The grating surface is highly susceptible to damage. Only hold it by the edges during handling. Wear latex gloves or finger cots to prevent surface contamination from hand stains. Never remove dust from the grating via contact cleaning methods. Slight surface imperfections that do not impair optical performance are permissible, and such gratings remain qualified.

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