PowerPhotonic (United Kingdom)

Freeform optics offer many advantages when performing complex beam shaping for directed energy applications. A number of design methods are presented utilizing radial basis functions, the Monge Ampere solution to optimal transport theory, as well as a novel phase wrapping approach. These methods allow for the precise manufacturing of singular optical elements such as collimation arrays and phase flatteners. This design study also outlines a modular solution in which multiple of these optics can be combined into a single, low-SWaP housing producing an array of aligned and collimated beams with a simulated power in the bucket of more than 80%.

The variance between a laser manufacturing process and the design intent is modelled using the linear machining law and Fourier filtering. We demonstrate model-driven compensation of machining errors for a freeform, engineered diffuser. © 2021 PowerPhotonic Ltd

Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text M. Currie, "Design, Fabrication and Simulation of Freeform Silica Micro-Optics," in Optical Design and Fabrication 2017 (Freeform, IODC, OFT), OSA Technical Digest (online) (Optica Publishing Group, 2017), paper FTh3B.1. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

We report a new route to obtaining custom freeform micro-optical components that is free from symmetry restrictions, offering drastically lower cost and delivery times than what is required by other freeform manufacturing methods. We describe how this process can be used to realize a complex custom optic using data generated directly from a design in Zemax. This surface is then extracted from Zemax and fabricated using the LightForge service before being measured. A quantitative analysis of the real optic is carried out both numerically and with the design source in Zemax, and we present a comparison between design and fabricated part performance.

High power laser beamshapers based on lens arrays are widely used to generate square, rectangular or hexagonal flat-top far-field beam profiles. These devices can provide high efficiency and excellent brightness preservation, but offer a limited range of far-field profiles and can suffer from diffraction-related artefacts when used with spatially-coherent beams. Diffractive optical elements (DOE) offer a far wider range of far-field profiles, and better speckle behavior, but bring performance trade-offs in terms of brightness, efficiency, scattered power and residual zeroth-order power. Freeform refractive optics offer additional choices in the design of high power laser beamshapers. Freeform lens arrays offer a wider range of beam profile options than that available from catalogue lens array parts. Freeform field mapping beamshapers can generate a wide range of application-specific beam profiles with high efficiency and, where required, minimal reduction in brightness. More complex quasi-random freeform surfaces can act as a pseudorandom refractive intensity mapping element (PRIME), providing a level of beamshaper design flexibility closer to that of DOEs, but without the related high-order scatter and zeroth order leakage. We describe the design and implementation of these different types of refractive beam shaper in fused silica, using PowerPhotonic's direct-write freeform fabrication process. This is ideal for use in high-power laser systems, where high damage threshold and low loss are essential. We compare and contrast the performance, benefits and limitations of these types of beamshaper, and describe how to select the ideal beamshaper type based on source coherence properties and application beam profile requirements.