Conference Agenda

Plasma jet polishing is a non-conventional method for reducing roughness of precision optics made of fused silica. The application of this method is demonstrated on two different optical elements: a conventionally ground freeform lens, and microlenses generated by selective laser etching. For both, the waviness and roughness were significantly reduced while the initial low-spatial wavelengths (surface contour) were preserved.

Imaging holographic waveguide systems can be used for special imaging applications when standard cameras are not suitable, e.g. for hyper spectral imaging or as a transparent camera system.

Dispersive volume Bragg gratings are used to couple light into and out of a waveguide to direct incident light to an image sensor. Due to the diffraction properties of the gratings the field of view of the system depends on the spectral range of the light source used.

This work analyses the correlation between the systems field of view and the propagation angle within the waveguide. The theoretical field of view is calculated using the grating parameters, simulated by performing a backward raytracing and compared to measured field of views of realized systems.

The use of VCSEL arrays in active imaging systems (e.g., time-of-flight cameras) requires compact, cost-efficient, and precise beam-shaping optics. Existing commercial solutions typically trade efficiency for spatial resolution: randomized microlens arrays/engineered diffusers are highly efficient but offer limited pattern control, whereas computer-generated holograms provide high pattern flexibility at reduced efficiency and increased sensitivity to wavelength and fabrication tolerances. A promising alternative is gradient-based optimization of parameterized freeform refractive surfaces.

Here, we demonstrate the fabrication and experimental validation of truncated hierarchical B-spline (THB-spline) based freeform microlens arrays for VCSEL-array beam shaping. The THB-spline representation enables local surface refinement, providing high spatial resolution while maintaining the efficiency of refractive optics. We design two beam shapers: an off-axis batwing stripe and a grid pattern. We implement them as an 80×80 microlens array (8 mm × 8 mm, 100 µm pitch). The lens arrays are fabricated by grayscale two-photon polymerization and characterized by confocal microscopy. Optical performance is evaluated under 940 nm VCSEL-array illumination using far-field camera measurements. The measured intensity distributions match the targets, and the fabricated surface profiles show good agreement with the design.

Modern optical fabrication technologies (OFTs) increasingly rely on localized, non-contact, and energy-driven processes, fundamentally changing the interaction between manufacturing processes and optical materials. Traditional glass processing maps, developed for brittle grinding and chemo-mechanical polishing, are no longer sufficient to guide material selection. This paper presents a first step towards an Optical Fabrication Process Map for Glasses, linking families of OFTs to the material properties required for their successful application. A structured classification of OFTs and their corresponding material demands is introduced as a framework for such a map. The concept is illustrated using local high-temperature polishing as a representative example. Material property maps demonstrate how suitable glasses can be identified based on thermomechanical criteria. The proposed approach establishes a foundation for systematically linking optical fabrication processes and glass materials, enabling improved process selection, targeted material development, and more efficient realization of high-performance optical systems.

In this paper, we propose an indentation-based method for fabricating lens array molds using sintered metal substrates. Whereas cast metals tend to generate pileups at the edges of impressions formed by indentation, such pileups are suppressed in sintered metals, which however exhibit surface pores that degrade surface quality. To overcome this issue, copper plating was applied to the workpiece surface to fill the surface pores. Indentation experiments were conducted by controlling the penetration depth of an indenter and the resulting impressions were evaluated. The results showed that lens elements were successfully formed without pileups, and the number of surface pores was significantly reduced by plating. Although the impression depth was smaller than the penetration depth owing to elastic recovery, the desired shape can be achieved by compensating for the penetration depth.

The manufacturing of silicon IR lens arrays on wafer level suffers from low yield and long processing times. This work presents an approach that utilizes the surface tension of a laser-induced silicon melt. Cylindrical preforms etched into a monocrystalline substrate are locally heated using laser radiation. A controlled cooling step is necessary to preserve the spherical shape of the melt which will otherwise result in deformations during solidification. The resulting lenses have been reproducibly made with diameters of up to 1 mm and up to 250 μm sagittal height with large crystallites or a complete monocrystalline structure.