A Graph-Based Laser Path Solver Algorithm for Virtual Reality Laboratory Simulations

TL;DR

This work presents femtoPro, a real-time VR laser laboratory that models pulsed beam propagation through a dynamic graph of optical elements using a CPU-based path solver. It introduces a selective updating strategy and memory pooling to efficiently update only altered portions of the beam graph while handling linear and second-order nonlinear optics, achieving real-time performance on mobile VR hardware. The authors derive memory and runtime cost models, validate them with benchmarks across multiple experimental setups, and analyze how edge dynamics and back-reflections constrain performance. The study demonstrates the practicality of dynamic graph based real-time simulations in educational VR environments and outlines future extensions to higher order nonlinearities and cavity simulations. Overall, the approach provides a scalable framework for interactive, physics-based, real-time simulations in dynamic graph structures.

Abstract

femtoPro is an interactive virtual reality (VR) laser laboratory balancing the contrasting challenges of accuracy and computational efficiency in optics simulations. It can simulate linear and nonlinear optical phenomena in real time, a task that pushes the boundaries of current consumer hardware. This paper details the concept, implementation, and evaluation of a dynamic graph-based solution tailored to the specific requirements and challenges of the simulation. Resource usage is optimized through a selective updating strategy that identifies and preserves laser paths unchanged between simulation frames, eliminating the need for unnecessary recalculations. Benchmarking of real-world scenarios confirms that our approach delivers a smooth user experience, even on mobile VR platforms with limited computing power. The methodologies, solutions and insights outlined in this paper may be applicable to other interactive, dynamic graph-based real-time simulations.

Figures (9)

• Figure 1: Collection of screenshots showing femtoPro's major features and interaction elements: (a) didactical tasks on the whiteboard, (b) experimental setup, (c) virtual laptop for controlling and analyzing experiments, (d) level folder for loading, saving, and restarting experimental levels, (e)--(i) optical elements, such as (e) laser source, (f) lens, (g) mirror, (h) beam blocker, (i) power meter, (j)--(n) user interactions, such as (j) teleporting, (k) inputting a number, (l) locking a screw, (m) fine and (n) coarse adjustment of an optical element. For snippets (e)--(n), a white background was added to enhance visual clarity. Further details are provided elsewhere femtoProArchitecture2023.
• Figure 2: Multiple-reflection scenario with red arrows depicting beam segments labeled in ascending order to illustrate the progression of the beam path.
• Figure 3: Schematic of a noncollinear autocorrelation setup, with beam segments from linear (red arrows) and second-order nonlinear optical responses (purple arrow).
• Figure 4: Graph representation of Fig. \ref{['fig:cavity_scheme']} with black arrows for directed edges and grey circles for nodes.
• Figure 5: Graph representation of Fig. \ref{['fig:nlc_scheme']} with black arrows for directed edges and grey circles for nodes.