"Littrow configuration” is the name given to those optical systems containing a reflective grating in which the orientation of the grating is such that the working order (most often the first diffraction order) travels back along the direction of the incident beam. This can be useful for various different applications, for example, in the context of laser resonators, where the grating can act as one of the mirrors of the resonator, or in monochromators and spectrometers.
In this week’s newsletter, we present two examples related to gratings in Littrow configuration. In the first, we demonstrate how to employ the Parameter Coupling tool in VirtualLab Fusion to ensure that the Littrow condition is fulfilled, by automatically adjusting the orientation of the grating, and the orientation and position of the detectors according to the wavelength and grating period. In the second example, we go over the optimization of a grating intended for use under Littrow configuration, where the goal is to design the grating structure so as to minimize its polarization effects.Read more
Gratings are a fundamental component of many classical and modern optical systems, like those in the field of spectrometry or near-eye displays. A characteristic feature of gratings is their sensitivity to the polarization state of the incoming light, and their strongly vectorial behavior in general.
Regardless of whether this effect is desired or detrimental, the fast physical optics software VirtualLab Fusion has got you covered: First of all, through its consistent vectorial treatment, not only of the field and the grating itself, but of the whole optical system which the grating may be a part of. Second, because VirtualLab Fusion offers the necessary tools to analyze in detail the vectorial behavior of your gratings.
In the examples below, we show an in-depth introduction of the
Polarization Analyzer – a powerful tool in the Grating Optical Setup that allows the user to calculate the efficiencies of grating orders with respect to different polarization states, with additional options to study the role of the wavelength and angle of incidence – and an investigation of the polarization effects of slanted gratings.
For an accurate and fast simulation of the propagation of light through complex optical systems, VirtualLab Fusion uses a “Connecting Field Solvers” approach that comprises the implementation of specific electromagnetic field solvers in both domains (space and spatial frequency). In this week’s newsletter we introduce the System Modeling Analyzer, a tool that allows the optical engineer to track the progress of the field (and its plane-wave spectrum) in detail as it propagates through their system. This can be incredibly useful for troubleshooting, as well as to gain additional insight into the behavior of a system. Additionally, we demonstrate the capabilities of VirtualLab Fusion to automatically select the best-suited Fourier transform algorithm wherever the operation is needed for the simulation, based on accuracy and computational effort criteria which can be adjusted by the user. We also show where to check which Fourier transform algorithms were selected. For more information, take a look at the use cases below!Read more
Analysis and Optimization of Lightguides for Augmented & Mixed Reality
16 February 2022 | 10:00 and 18:00 (CET)
Lightguides for AR & MR with Holographic and Surface-Relief Grating Couplers
23 February 2022 | 10:00 – 17:45 (CET)
In the past weeks we have shown the powerful capabilities of the fast physical optics modeling and design software VirtualLab Fusion for the design and simulation of lightguide systems. We now culminate this campaign with a demonstration of the application of these technologies to simulate examples from literature with complex eye-pupil-expander (EPE) regions.
See below two examples, one containing a setup with a “butterfly" EPE, that splits the field of view (FOV), and another one illustrating a 2D-periodic diamond-shaped grating structures in the combined expander/outcoupler region.Read more
In our last newsletter we highlighted the capabilities of the fast physical optics software VirtualLab Fusion to analyze the performance of lightguide systems. This time we address a closely related step in the design workflow: the optimization of the grating geometries used in the coupling and expansion regions of the system.
VirtualLab Fusion offers a series of powerful tools for this task: for instance, detectors that calculate fundamental merit functions like uniformity and efficiency, and moreover the possibility to implement a (custom) smooth variation of the grating parameters along a specific region of the layout. The latter approach can drastically decrease the number of free parameters in the optimization while at the same time retaining crucial flexibility. For more information, check out the examples below!Read more
The design process of any optical system must include an investigation of the performance of the system as a crucial step. Of course, this includes lightguide devices for applications in the field of augmented and mixed reality (AR/MR), as relatively complex representatives of optical systems. Depending on the application, “performance” can be defined by different merit functions. VirtualLab Fusion provides the optical engineer with a set of helpful tools and detectors to investigate the properties of the system.
Below we demonstrate two examples centered around the performance evaluation of lightguides: an NED (“near to exe”) device with 2D pupil expansion and a human eye model in order to calculate the MTF & PSF, and another one on characterization of the lateral uniformity.Read more
The Light Guide Toolbox of the fast physical optics software VirtualLab Fusion provides a series of tools to help the optical engineer with many of the different stages involved in the design of lightguide devices for augmented and mixed reality applications. In our recent newsletters we already covered some of the features that assist, for instance, in the determination of a sufficient layout for the lightguide and its grating regions.
Today we turn to one of the most powerful systematic design tools for gratings in lightguides: the Footprint and Grating Analysis tool. Among its many functions, which are not limited to any particular layout, it can help, for example, to visualize the interactions of the beam footprints with the grating regions for the different field-of-view modes – an important study, considering the complex propagation of light inside the lightguide. But the jewel in its crown is its capacity to perform an analysis of the grating behavior that can then be used to configure a smooth variation of the grating parameters inside a single grating region, with the aim of improving the performance of the device in terms of its uniformity and efficiency.
Learn more about it with the use cases below!Read more