LightTrans (Germany)

Amidst the mixed news surrounding the feasibility of Augmented Reality (AR) smart glasses, the demand for commercially viable mass production of industry-standard optical waveguide combiners remains unwavering. Over the past two years, our consortium of companies has proposed a cost-effective and scalable manufacturing process for Surface Relief Grating (SRG) based waveguides, offering a comprehensive path from concept to fabrication through large-area nanoimprinting. This approach has garnered significant interest from both customers and partners associated with the participating companies. Our aim is to push beyond the established limits of large-area nanoimprinting. In this work we address the obstacles and latest advancements in maintaining imprint quality, fidelity and uniformity during large-area nanoimprinting. We demonstrate various building blocks that are crucial to manufacture high quality and cost-effective AR waveguides, such as the replication of slanted gratings and the possibility of low residual layer thickness using large-area nanoimprint lithography. We employ high refractive index materials, such as resin and glass (1.8, 1.9 and 2.0), and also explore a lighter and flatter version of the RealView 1.9 glass. Our primary objective is to demonstrate that large-area nanoimprinting not only presents itself as a novel method for high-volume manufacturing of SRG waveguides but also enables the production of challenging optics for AR smart glasses.

Nanoimprinting of surface-relief grating-based waveguides has the potential to produce one of the industry-leading augmented reality (AR) smart glasses, but there are still many challenges in the design, scaling, and reproducibility of these imprinted waveguides. A promising path toward mass manufacturing of optical waveguide combiners is via large-area nanoimprinting. Here, we present the complete value chain with partners involved throughout the process: from design, mastering, and materials to imprinting and metrology, to prove that this method improves not only the manufacturing throughput but also the waveguide quality. We demonstrate that the replication and image quality are true to the intended design using large area, high refractive index (n ¼ 1.9), square (300 mm × 300 mm) glass substrates with high-refractive index resins (n ¼ 1.9). This is shown to be valid for over 100 replications and for large area nanoimprinting (Gen5, 1100 mm × 1300 mm). Our goal is to demonstrate a viable path toward high-volume and low-cost manufacturing of AR waveguides based on surface relief gratings.

LightTrans offers solutions for modeling & design in optics & photonics. Our products& services include optical engineering, training, consulting & our software VirtualLab Fusion - a platform for connecting inbuilt & customized electromagnetic field solvers. This approach enables fast physical optics with ray tracing embedded in a well-defined way. Fields of application: diffraction, interference, coherence, & polarization in your modelling & design of AR & VR lightguide glasses, microscopy etc. Get in contact with us: LightTrans International UG Kahlaische Strasse 4 Jena 07745 Germany Website: www.lighttrans.com Email: info@lighttrans.com Phone: +49 36 41 5312950 LinkedIn Profile: https://www.linkedin.com/company/lighttrans Twitter Profile: https://twitter.com/LightTrans Subscribe to our Newsletter: www.lighttrans.com/newsletter

The Gouy phase shift has remained an object of fascination since its discovery by the eponymous scientist at the end of the nineteenth century. The reason behind this uninterrupted interest resides, at least in part, in the fact that the Gouy effect is to be found in the borderland between geometrical optics and diffractive behavior. Using purely mathematical arguments in a full electromagnetic solution to the propagation problem, it is possible to derive a formula where all the physical effects that we know must appear are laid bare, including the Gouy phase. Additionally, by discarding the field information, this formula retrieves the ray-tracing result, and in doing so vindicates the predictions that geometrical optics can make, of the ray mapping and optical path length accretion. The resulting analysis helps overcome the geometrical-physical optics dichotomy in our understanding of the Gouy phenomenon.

One of the major challenges faced by externally occulted solar coronagraphs is the suppression of the light diffracted by the occulter edge. It is a contribution to the stray light that overwhelms the coronal signal on the focal plane and must be reduced by modifying the geometrical shape of the occulter. There is a rich literature, mostly experimental, on the appropriate choice of the most suitable shape. The problem arises when huge coronagraphs, such as those in formation flight, shall be tested in a laboratory. A recent contribution [Opt. Lett.41, 757 (2016)OPLEDP0146-959210.1364/OL.41.000757] provides the guidelines for scaling the geometry and replicate in the laboratory the flight diffraction pattern as produced by the whole solar disk and a flight occulter but leaves the conclusion on the occulter scale law somehow unjustified. This paper provides the numerical support for validating that conclusion and presents the first-ever simulation of the diffraction behind an occulter with an optimized shape along the optical axis with the solar disk as a source. This paper, together with Opt. Lett.41, 757 (2016)OPLEDP0146-959210.1364/OL.41.000757, aims at constituting a complete guide for scaling the coronagraphs' geometry.

Birefringence effects can have a significant influence on the polarization state as well as on the transversal mode structure of laser resonators. This work introduces a flexible, fast and fully vectorial algorithm for the analysis of resonators containing homogeneous, anisotropic optical components. It is based on a generalization of the Fox and Li algorithm by field tracing, enabling the calculation of the dominant transversal resonator eigenmode. For the simulation of light propagation through the anisotropic media, a fast Fourier Transformation (FFT) based angular spectrum of plane waves approach is introduced. Besides birefringence effects, this technique includes intra-crystal diffraction and interface refraction at crystal surfaces. The combination with numerically efficient eigenvalue solvers, namely vector extrapolation methods, ensures the fast convergence of the method. Furthermore a numerical example is presented which is in good agreement to experimental measurements.

The optimization of multi-parameter resonators requires flexible simulation techniques beyond the scalar approximation. Therefore we generalize the scalar Fox and Li algorithm for the transversal eigenmode calculation to a fully vectorial model. This modified eigenvalue problem is solved by two polynomial-type vector extrapolation methods, namely the minimal polynomial extrapolation and the reduced rank extrapolation. Compared to other eigenvalue solvers these techniques can also be applied to resonators including nonlinear components. As an example we show the calculation of an azimuthally polarized eigenmode emitted by a resonator containing a discontinuous phase element and a nonlinear active medium. The simulation is verified by experiments.

Crystals are widely applied in laser systems and they play important roles as polarization manipulators. A simple uniaxial crystal plate with a certain thickness may serve as a linear/circular polarizer. A uni/biaxial crystal with a proper orientation may work as a polarization beam splitter/combiner. A biaxial crystal at conical refraction may be used to generate radially polarized light or help form a Bessel beam. To design a laser system including crystal component(s), or to optimize the performance of such a system, simulation techniques which models the light propagation through crystals is required. We present a full-vectorial and electromagnetic method that enables the modeling of crystal components with general laser fields, based on the angular spectrum of plane waves. Propagation of general field within anisotropic media and the reflection and transmission at a planar interface between isotropic/anisotropic and anisotropic/anisotropic media are discussed. We demonstrate examples on how crystals are used to manipulate the polarization state of laser beams.

The propagation of harmonic fields through homogeneous media is an essential simulation technique in optical modeling and design by field tracing, which combines geometrical and physical optics. For paraxial fields the combination of Fresnel integral and the Spectrum of Plane Waves (SPW) integral solves the problem. For non- paraxial fields the Fresnel integral cannot be applied and SPW often suffers from a too high numerical effort. In some situations the far field integral can be used instead, but a general solution of the problem is not known. It is useful to distinguish between two basic cases of non-paraxial fields: 1) The field can be sampled without problems in the space domain but it is very divergent because of small features. A Gaussian beam with large divergence is an example. 2) The field possesses a smooth but strong phase function, which does not allow its sampling in space domain. Spherical or cylindrical waves with small radius of curvature are examples. We refer to such fields as fields with a smooth phase term. The complete phase is the sum of the smooth phase term and the residual. For both cases we present a parabasal field decomposition, in order to propagate the field. In the first case we perform the decomposition in the Fourier domain and in the second case in the space domain. For each of the resulting parabasal fields we separate a linear phase factor which has not to be sampled. In order to propagate the parabasal fields we present a rigorous semi-analytical SPW operator for parabasal fields, which can handle the linear phase factors without sampling it at any time. We show that the combination of the decomposition and this modified SPW operator enables an ecient propagation of non-paraxial fields. All simulations were done with the optics software VirtualLab™.