Nonsequential Modeling for Multi-Reflection Systems

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.

Modeling of a Herriott-Cell

This use case shows a physical optics simulation of a Herriott cell for gas spectroscopy, including a demonstration with CO2.

Investigation of Sodium D Lines with a Fabry-Pérot Etalon

An optical metrology system with a silica spaced etalon is set up to measure the sodium D lines in VirtualLab Fusion. Furthermore, the influence of the reflectance of real coatings is investigated.

11 – 15 September | Summer Course

11 – 15 September | Summer Course