Refractive index modulation modification in a holographic grating

A grating comprising:

• a polymer layer comprising:
• a first region characterized by a first refractive index;
• a second region characterized by a second refractive index, the second refractive index being higher than the first refractive index;
• and
• a plurality of nanoparticles dispersed in the polymer layer, the nanoparticles having a higher concentration in proximity to a surface of the polymer layer in one or more of the first region or the second region, such that a refractive index modulation of the grating is apodized.

A holographic grating comprising:

• a polymer layer comprising:
• a first region characterized by a first refractive index;
• a second region characterized by a second refractive index, the second refractive index being higher than the first refractive index;
• and
• a plurality of nanoparticles dispersed in the polymer layer,
• wherein:
• the nanoparticles have a higher concentration in the second region and the nanoparticles have a third refractive index that is higher than the second refractive index;
• or
• the nanoparticles have a higher concentration in the first region and the nanoparticles have a fourth refractive index that is lower than the first refractive index.