A grating coupler may be fabricated by exposing a photopolymer layer to grating forming light for forming periodic refractive index variations in the photopolymer layer. The photopolymer layer may be exposed to apodization light for reducing an amplitude of the periodic refractive index variations in a spatially-selective manner. The apodization may also be achieved or facilitated by subjecting outer surface(s) of the photopolymer layer to a chemically reactive agent that causes the refractive index contrast to be reduced near the surface(s) of application. The apodized refractive index profile of the gratings facilitates the reduction of optical crosstalk between different gratings of the grating coupler.

A grating coupler may be fabricated by exposing a photopolymer layer to grating forming light for forming periodic refractive index variations in the photopolymer layer. The photopolymer layer may be exposed to apodization light for reducing an amplitude of the periodic refractive index variations in a spatially-selective manner. The apodization may also be achieved or facilitated by subjecting outer surface(s) of the photopolymer layer to a chemically reactive agent that causes the refractive index contrast to be reduced near the surface(s) of application. The apodized refractive index profile of the gratings facilitates the reduction of optical crosstalk between different gratings of the grating coupler.

A process of forming an identification marking within article formed from an at least partially optically transparent material for identification and validation, said process including the steps of (i) forming an indicia with an at least partially optically transparent material by way of subsurface laser engraving (SSLE); and (ii) forming a plurality of defects within or adjacent indicia within said at least partially optically transparent material resultant of the step of forming the indicia and from localized heating and irregularities in said at least partially optically transparent material, wherein said plurality of defects forms said identification marking

An optical coupler includes a plurality of volume gratings in a substrate. The gratings include an array of fringes extending along length and thickness dimensions of the substrate. A difference between a refractive index of the fringes and a refractive index of the substrate depends on a depth coordinate along the thickness dimension of the substrate. A dependence of the difference on the depth coordinate has a bell-shaped function which suppresses ghost image formation due to optical crosstalk between gratings of neighboring spatial pitches.

A grating coupler may be fabricated by exposing a photopolymer layer to grating forming light for forming periodic refractive index variations in the photopolymer layer. The photopolymer layer may be exposed to apodization light for reducing an amplitude of the periodic refractive index variations in a spatially-selective manner. The apodization may also be achieved or facilitated by subjecting outer surface(s) of the photopolymer layer to a chemically reactive agent that causes the refractive index contrast to be reduced near the surface(s) of application. The apodized refractive index profile of the gratings facilitates the reduction of optical crosstalk between different gratings of the grating coupler.

We describe methods of mass-producing full color, 3D holograms, potentially incorporating a personalized image, which are particularly suitable for security purposes. Broadly speaking in embodiments a method generates, electronically, an interlaced image comprising a set of different views of a 3D object from different angles. This is projected onto a diffusing screen using coherent light and mapped from the screen into an angularly encoded object beam using a lenticular array. The different views in the angularly encoded object beam are then recorded simultaneously into holographic film using a reference beam.

A process of forming an identification marking within article formed from an at least partially optically transparent material for identification and validation, said process including the steps of (i) forming an indicia with an at least partially optically transparent material by way of subsurface laser engraving (SSLE); and (ii) forming a plurality of defects within or adjacent indicia within said at least partially optically transparent material resultant of the step of forming the indicia and from localized heating and irregularities in said at least partially optically transparent material, wherein said plurality of defects forms said identification marking.