A pioneering international optical design company based in Israel, Holo/Or designs and manufactures diffractive optical elements (DOEs) and micro-optical elements used worldwide for sophisticated applications involving high-precision and high-power lasers. Holo/Or was experiencing some challenges in modeling realistic systems for diffraction-limited results. But the company developed an ingenious solution—use of the bidirectional scattering diffusion function (BSDF) to simulate and optimize multi-mode (or single-mode) lasers using geometric ray tracing. As described in their whitepaper, “Method for Laser Source Definition in Zemax,” this approach enables Holo/Or to quickly achieve accurate results for factors like realistic spot-size at lens foci while accounting for wave optics effect and also allowing for simple system optimization.

The goal: Improving system performance for complex illumination systems

A Diffractive Optical Element (DOE) uses thin micro-structure patterns to alter the phase of light propagated through it, manipulating the light to almost any intensity profile or shape. DOEs enable capabilities which are not feasible with standard refractive optics.

Holo/Or offers a vast variety of diffractive optics products, including beam splitters, beam shapers (Top Hat), homogenizers/diffusers, multi-focal, beam samplers, and vortex lenses. Customers around the world use their products for applications in medicine, materials processing, and measurement solutions.

The challenge: How to model multi-mode lasers in sequential mode

No software program can be all things to all people. However, OpticStudio is designed to provide users with the utmost flexibility in meeting their unique needs—for example, enabling designers to work in either sequential or non-sequential mode in a single interface, and making it easy to customize the application through a built-in API.

Multi-mode lasers are complex because of their arbitrary amplitude and phase. Characterizing such lasers in geometrical ray tracing is challenging, whether in sequential and non-sequential mode. Holo/Or was encountering issues in attempting to do this using standard geometric ray tracing in OpticStudio, namely they were obtaining incorrect laser spot dimensions and distorted shaped intensity distributions, as well as suffering wasted cycles of custom beam shaper design and production. The alternative design approach of using physical optics propagation was not practical due to the significant time delays in modeling, geometry limitations, and the need to propagate each mode of the multi-mode beam individually.

The solution: Simulation modeling of multi-mode beams using geometrical ray tracing with additional angular scattering

Recognizing that the underlying challenge of modeling physical optics is due to inherent limitations of time and computer memory, Holo/Or determined that a workable solution lay in modeling real beams using geometrical ray tracing with additional angular scattering to get realistic beam size values along the entire optical path.

The basic idea was to apply a wavefront shape that is uncorrelated with all other optical parts within the optical system. After exploring several options, they discovered the most effective approach to be modeling the multi-mode effect using BSDF-type scattering. Using this approach, they were able to achieve diffraction-limited results and correctly models realistic systems.

Holo/Or has successfully used this approach for a variety of components, including:

Welding beam-shaping projects by dual spots welding: Simulating the spot size and overlapping

Parallel processing soldering: Spot size and overlapping

Axicon-based system for ring shaping: Ring-thickness simulation

Focusing system: Aberrations and spot size analysis

Top Hat beam shaping: Transfer region analysis

Structured light modules: Controlling overlapping condition

Lens array homogenizer

We at Zemax admire the ingenious way Holo/Or has used OpticStudio to solve a specific design challenge. Please read their full white paper for further details, including specific case studies to show the effectiveness and limits of their solution for realistic geometric beam shaping.

Learn more…

Read the Holo/Or white paper for details on how they did it

Watch a Webinar about simulating lasers in OpticStudio 

*Beam image courtesy of Holo/Or