| 摘要 |
A planar and fiber optical grating structure fabrication apparatus uses non-precision substrate material while providing high optical precision phase mask and grating capability with dramatically reduced cost of material and production. The phase mask is a volume hologram resulting from refractive index change in the media. When apodized, the volume hologram phase mask incorporates a change in diffraction efficiency along its length, without a reduction in the average transmittance through the mask, thus providing a uniform average refractive index of the resultant grating structure along its full length. The phase mask intrinsically produces exactly two diffraction orders, is functional over a wide wavelength range without substantive interference from undesired diffraction orders while still maintaining adequate quality of the structure being inscribed.
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