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The rising production and consumption of data worldwide is posing challenges on how it can be efficiently analyzed and absorbed on a human scale. Emerging technologies in data visualization are rapidly expanding to try to address this problem. One technology in particular, Augmented Reality (AR) glasses, has the capacity to allow individuals to process live virtual information while keeping an eye on their surrounding environment. Our team has recently presented a unique retinal projection concept for augmented reality applications1. The concept combines a photonic integrated circuit (PIC) and holography. The photonic integrated circuit is made of silicon nitride (Si3N4) for its ability to guide visible wavelengths2 (λ = 532 nm in our case) and its compatibility with the CMOS fabrication process technology. In our concept, the role of this circuit is to distribute and extract light at specific locations on the surface of a glass. The light emissions pass through a holographic layer deposited on the surface of the photonic circuit. The holographic layer is made of a 2D array of small individual holograms. The role of the hologram is to modify the light properties (emission angle, phase…) of the light emissions from the PIC in order to generate a composite plane wavefront. The eye can focus this wavefront on the retina even at a small eye relief distance (few centimeters). The focused wavefront represents one pixel of the projected retinal image. Several emissive point distributions on the surface of the PIC will create a full 2D retinal image. The retinal projector concept is schematically described in fig.1. Until now, both parts of the AR glass – the PIC and the holographic layer – have been developed independently3,4,5. In previous work6, the basic building blocks of the circuit were designed both analytically and with numerical simulations: single-mode waveguide, MMI (MultiMode Interference) coupler, diffraction gratings and more. This paper presents in section 2 the design and numerical simulations of a double-tip edge coupler at λ = 532 nm. This additional component will be useful to couple light in our future prototypes with a compact design. In section 3, it is combined with previously designed PIC building blocks to design a unique device dedicated to evaluate the interaction between a silicon nitride PIC and a hologram.
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