Jesper Glückstad

We consider highly localised features of the electromagnetic field, that is, features on the order of a wavelength. Highly localised features are particularly interesting for the computation of plasmonic resonances and the analysis of photonic nanojets. Computing highly localised features of the electromagnetic field is challenging for conventional methods such as FEM because of the need to refine the entire mesh and to use ad hoc numerical solutions to truncate open domains. We define a computational setup and give some theoretical background for the modified Born series approach based on the vectorial Lippmann-Schwinger equation, including a constant overrelaxation parameter, still guaranteeing convergence. We stress that the purpose is to introduce and illustrate a practically computable sufficient method for a constant overrelaxation parameter to make the MBS convergent and not to argue that it is competitive in its present form with the existing methods.

Several 3D light-based printing technologies have been developed that rely on the photopolymerization of liquid resins. A recent method, so-called Tomographic Volumetric Additive Manufacturing, allows the fabrication of microscale objects within tens of seconds without the need for support structures. This method works by projecting intensity patterns, computed via a reverse tomography algorithm, into a photocurable resin from different angles to produce a desired 3D shape when the resin reaches the polymerization threshold. Printing using incoherent light patterning has been previously demonstrated. In this work, we show that a light engine with holographic phase modulation unlocks new potential for volumetric printing. The light projection efficiency is improved by at least a factor 20 over amplitude coding with diffraction-limited resolution and its flexibility allows precise light control across the entire printing volume. We show that computer-generated holograms implemented with tiled holograms and point-spread-function shaping mitigates the speckle noise which enables the fabrication of millimetric 3D objects exhibiting negative features of 31 μm in less than a minute with a 40 mW light source in acrylates and scattering materials, such as soft cell-laden hydrogels, with a concentration of 0.5 million cells per mL.

Photonic nanojets (PNJs) are highly localized optical probes that promise label-free measurements beyond the classical diffraction limit. We here demonstrate numerically the feasibility of label-free, self-calibrating, super-resolution optical detection and imaging using far-field scatterometry in conjunction with rapid scanning photonic nanojet excitation achieved with no opto-mechanical intervention. We realize PNJ scanning by computed structured illumination of refractive dielectric micro-elements such as micro-spheres and micro-cubes. Our far-field measurement data are phaseless. In proof-of-concept computations, we use our steerable optical probe to extract information on nanoparticles, aggregates of nanoparticles, and thin-film structures beyond the classical lateral and vertical resolution limits, in the presence of supporting structures such as substrates.

We present the option to use the patented [1, 2] Computer Generated Holography (CGH) modality, HoloTile, as a better alternative light delivery system for volumetric additive manufacturing (VAM). Holographic light delivery promises many of the qualities sought after in VAM, including higher photon efficiency, inherent wavefront shaping, full point spread function control, and lower mechanical complexity. These qualities, along with the unique control that is gained with HoloTile, may allow for the use of low-power light sources at low print times with real-time aberration and scattering compensation.

HoloTile is our novel and recently patent-filed approach [1,2] to obtain very fast reconfigurable and strongly speckle-reduced digital holography. Using HoloTile we have experimentally demonstrated more than 90 % photon-efficient phase-only projected dynamic and static far field diffraction both with and without a lens. A key aim for inventing and innovating HoloTile has been to effectively solve the challenge of rapid and speckle-free coherent or semi-coherent light sculpting without the need for time-averaging techniques - a challenge that exists in several fields of optics and photonics. In particular, HoloTile provides four new unique key features as CGH-modality for high-resolution spatial light modulators, reconfigurable DOEs or new meta-surface MOEs: • A 100x speed improvement over standard CGH-modalities • Substantial speckle reduction by matched tiling and PSF-shaping • Real-time dynamic and output 'pixel' discretized digital holograms • Lens-free scaling or zoom by software adapted HoloTile phase-encoding.

Light-based technologies for 3D printing have recently been developed and are leading the field thanks to their unmatched performance. However, these techniques are still limited to using incoherent light patterning for printing. Here, we present a novel approach that allows us to print using coherent patterns by combining light-beam shaping and tomographic projections. We demonstrate this concept with a volumetric printer based on reverse tomography using a Digital Micromirror Device (DMD) in a holographic configuration. The Lee holograms method allowed us to use the DMD as a fast phase modulator and the HoloTile approach to achieve fast and speckle-reduced holograms.

HoloTile is a patented computer generated holography approach with the aim of reducing the speckle noise caused by the overlap of the non-trivial physical extent of the point spread function in Fourier holographic systems from adjacent frequency components. By combining tiling of phase-only of rapidly generated sub-holograms with a PSF-shaping phase profile, each frequency component—or output ‘pixel’— in the Fourier domain is shaped to a desired non-overlapping profile. In this paper, we show the high-resolution, speckle-reduced reconstructions that can be achieved with HoloTile, as well as present new HoloTile modalities, including an expanded list of PSF options with new key properties. In addition, we discuss numerous applications for which HoloTile, its rapid hologram generation, and the new PSF options may be an ideal fit, including optical trapping and manipulation of particles, volumetric additive printing, information transfer and quantum communication.

HoloTile is a patented computer generated holography approach with the aim of reducing the speckle noise caused by the overlap of the non-trivial physical extent of the point spread function in Fourier holographic systems from adjacent frequency components. By combining tiling of phase-only of rapidly generated sub-holograms with a PSF-shaping phase profile, each frequency component - or output "pixel" - in the Fourier domain is shaped to a desired non-overlapping profile. In this paper, we show the high-resolution, speckle-reduced reconstructions that can be achieved with HoloTile, as well as present new HoloTile modalities, including an expanded list of PSF options with new key properties. In addition, we discuss numerous applications for which HoloTile, its rapid hologram generation, and the new PSF options may be an ideal fit, including optical trapping and manipulation of particles, volumetric additive printing, information transfer and quantum communication.