Interlayers that exhibit superior properties and that provide desirable optical properties when incorporated into laminates, such as windshields, windows or other glazings containing a holographic optical element (HOE) are disclosed. The interlayers, when used in a laminate in conjunction with the HOE film, maintain and do not detract from the HOE film properties.

A system is provided. The system includes a light source configured to emit an infrared light to illuminate an eye of a user. The system includes a grating disposed facing the eye and including a birefringent material film configured with a uniform birefringence lower than or equal to 0.1. The grating is configured to diffract the infrared light reflected from the eye, and transmit a visible light from a real world environment toward the eye, with a diffraction efficiency less than a predetermined threshold. The system includes an optical sensor configured to receive the diffracted infrared light and generate an image of the eye based on the diffracted infrared light.

The disclosure provides recording materials including propane derivatized monomers and polymers for use in volume Bragg gratings, including, but not limited to, volume Bragg gratings for holography applications. Several structures are disclosed for propane derivatized monomers and polymers for use in Bragg gratings applications, leading to materials with higher refractive index, low birefringence, and high transparency. The disclosed propane derivatized monomers and polymers thereof can be used in any volume Bragg gratings materials, including two-stage polymer materials where a matrix is cured in a first step, and then the volume Bragg grating is written by way of a second curing step of a monomer.

The disclosure provides recording materials including mono- or poly-phenyl-core derivatized monomers and polymers for use in volume Bragg gratings, including, but not limited to, volume Bragg gratings for holography applications. Several structures are disclosed for mono- or poly-phenyl-core derivatized monomers and polymers for use in Bragg gratings applications, leading to materials with higher refractive index, low birefringence, and high transparency. The disclosed mono- or poly-phenyl-core derivatized monomers and polymers thereof can be used in any volume Bragg gratings materials, including two-stage polymer materials where a matrix is cured in a first step, and then the volume Bragg grating is written by way of a second curing step of a monomer.

Techniques disclosed herein relate to holographic optical materials and elements. An example of a holographic recording material includes matrix monomers characterized by a first refractive index and configured to polymerize to form a polymer matrix, writing monomers dispersed in the matrix monomers and characterized by a second refractive index different from the first refractive index, and a photocatalyst for controlled radical polymerization of the writing monomers. The writing monomers are configured to polymerize upon exposed to recording light. The photocatalyst is dispersed in the matrix monomers. The photocatalyst includes, for example, a transition metal photocatalyst or a metal-free organic photocatalyst, such as a photocatalyst for atom transfer radical polymerization or a transition metal photocatalyst for addition fragmentation chain transfer polymerization.

Techniques disclosed herein relate to modifying refractive index modulation in a holographic optical element, such as a holographic grating. According to certain embodiments, a holographic optical element or apodized grating includes a polymer layer comprising a first region characterized by a first refractive index and a second region characterized by a second refractive index. The holographic optical element or apodized grating includes a plurality of nanoparticles dispersed in the polymer layer. The nanoparticles have a higher concentration in either the first region or the second region. In some embodiments, the nanoparticles may be configured to increase the refractive index modulation. In some embodiments, the nanoparticles may be configured to apodize the grating by decreasing the refractive index modulation proximate to sides of the grating. The refractive index may be modulated by applying a monomer reservoir buffer layer to the polymer layer, either before or after hologram fabrication.

The disclosure provides recording materials include fluorene derivatized monomers and polymers for use in volume Bragg gratings, including, but not limited to, volume Bragg gratings for holography applications. Several fluorene structures are disclosed: simply substituted fluorenes, cardo-fluorenes, and spiro-fluorenes. Fluorene derivatized polymers in Bragg gratings applications lead to materials with higher refractive index, low birefringence, and high transparency. Fluorene derivatized monomers/polymers can be used in any volume Bragg gratings materials, including two-stage polymer materials where a matrix is cured in a first step, and then the volume Bragg grating is written by way of a second curing step of a monomer.

The present invention provides in one aspect holographic materials comprising a covalent adaptable networks (CAN) matrix that has exchangeable crosslinks, and at least one writing monomer, wherein upon exposure to a stimulus, the holographic material can undergo photopolymerization and serve as a recording medium.

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.

The present disclosure relates to a hologram recording medium having a main relaxation temperature (Tr) of 0° C. or less, wherein the Tr is a point where a rate of change of phase angle with respect to temperature is the largest in a range of −80° C. to 30° C. in dynamic mechanical analysis. The present disclosure also relates to an optical element including the same and a holographic recording method using the hologram recording medium.