Optical Design Software - VirtualLab Fusion

Hybrid lenses combine the advantages of classic refractive components and diffractive structures, and hence have become a promising approach in different optical applications, such as intraocular lens implants for treatment of cataracts. In particular, the opposite signs of the dispersion for refractive and diffractive surfaces enable the correction of chromatic aberrations.

In order to model and design such a hybrid element accurately, the in-depth analysis of diffraction effects through the system is a necessity. This includes the evaluation of diffraction efficiencies of real structures in combination with the fast and accurate calculation of the point-spread function (PSF). VirtualLab Fusion’s highly flexible approach of interoperable modeling techniques on a single platform is key to enable the precise and quick modeling of classic lenses and calculation of the diffraction efficiencies of the different orders of a diffractive lens.

To illustrate the capabilities of the software in this regard, the near and far field view of a designed hybrid lens are analyzed in the example. Moreover, the effect of varying the height of the designed binary element on the diffraction efficiencies is investigated to further optimize the optical function. In order to evaluate the resulting PSFs similar to the perception of a human eye, photometric quantities, such as illuminance and luminous flux, are used, which can easily be determined with the help of VirtualLab’s flexible detector concept.

Dot projectors, capable of splitting an incoming beam into a densely populated array of discrete spots, have seen a rapid increase in applications in recent history. To achieve the required high number of spots, these devices typically combine highly divergent source panels with beam splitters.

Striking the right balance between accuracy and speed in the simulation of systems like these can be quite challenging: On the one hand, the small structures of the beam splitter demand the application of rigorous methods, which tend to be computationally heavy. On the other, the simulation should be agile enough to produce results within reasonable bounds of memory use and time. Besides, often, the system will comprise not just the dot projector, but also, at least, propagation in free space, if not other, additional, optical components, such as lenses.

The extremely flexible approach of interoperability of modeling techniques on a single platform offered by the optical modeling and design software VirtualLab Fusion is just the ticket here. It permits the application of the rigorous Fourier Modal Method/Rigorous Coupled Wave Analysis (FMM/RCWA) to model the non-paraxial splitter with the necessary accuracy, while at the same time avoiding computational overkill by combining this technique with other, much faster, approaches for other potential elements in the system, whether they be propagation in free space, through lenses, or both. And all of this on a single software platform with a consistent light model, meaning that no important information is lost changing from one modeling technique to another, and also obviating the need for any cumbersome back-and-forth between different packages.

In this week’s newsletter we showcase just such a dot-projector system, providing both an analysis of the working principle of the device and a document covering its design.

Nonsequential optical systems, particularly those where the nonsequentiality comes from the presence of multiple internal reflections inside a component, pose their own specific set of challenges. Decomposing such systems into a sequential equivalent is often immensely inconvenient, and always impractical. Having an inherently nonsequential modeling strategy at our disposal can, then, become a huge advantage when faced with tasks of this kind.

The modeling and design software VirtualLab Fusion offers precisely this with its Manual Channel Configuration mode, in which the so-called “Light Path Finder” performs a preliminary analysis of the paths that the light follows inside a nonsequential system, using a user-controlled energy-based criterion to determine which paths need to be followed further; this becomes particularly useful in asymptotic configurations with an infinite number of paths. The additional capacity granted to the user to open and close channels in the system at will (e.g., should only forward transmission be considered for this particular interface, or is backward reflection also of interest?) enhances the flexibility of the approach, allowing you to get results that are as accurate as needed, and as fast as possible.

In this week’s newsletter we demonstrate this concept using two different scenarios as examples. First, we show the case of a Herriott Cell, a resonator filled with weakly absorbing gas where a high number of roundtrips facilitates an accurate characterization of the absorption properties of the material. Secondly, we employ a Fabry-Perot etalon to resolve the sodium doublet.