Simon Thiele

Sub-micrometre accurate free-form optics by three-dimensional printing on single-mode fibres

Micro-optics are widely used in numerous applications, such as beam shaping, collimation, focusing and imaging. We use femtosecond 3D printing to manufacture free-form micro-optical elements. Our method gives sub-micrometre accuracy so that direct manufacturing even on single-mode fibres is possible. We demonstrate the potential of our method by writing different collimation optics, toric lenses, free-form surfaces with polynomials of up to 10th order for intensity beam shaping, as well as chiral photonic crystals for circular polarization filtering, all aligned onto the core of the single-mode fibres. We determine the accuracy of our optics by analysing the output patterns as well as interferometrically characterizing the surfaces. We find excellent agreement with numerical calculations. 3D printing of microoptics can achieve sufficient performance that will allow for rapid prototyping and production of beam-shaping and imaging devices.

3D-printed eagle eye: Compound microlens system for foveated imaging

A highly miniaturized vision system is realized by directly 3D-printing different multilens objectives onto a CMOS image sensor. We present a highly miniaturized camera, mimicking the natural vision of predators, by 3D-printing different multilens objectives directly onto a complementary metal-oxide semiconductor (CMOS) image sensor. Our system combines four printed doublet lenses with different focal lengths (equivalent to f = 31 to 123 mm for a 35-mm film) in a 2 × 2 arrangement to achieve a full field of view of 70° with an increasing angular resolution of up to 2 cycles/deg field of view in the center of the image. The footprint of the optics on the chip is below 300 μm × 300 μm, whereas their height is <200 μm. Because the four lenses are printed in one single step without the necessity for any further assembling or alignment, this approach allows for fast design iterations and can lead to a plethora of different miniaturized multiaperture imaging systems with applications in fields such as endoscopy, optical metrology, optical sensing, surveillance drones, or security.

Ultra-compact on-chip LED collimation optics by 3D femtosecond direct laser writing.

By using two-photon lithographic 3D printing, we demonstrate additive manufacturing of a dielectric concentrator directly on a LED chip. With a size of below 200 μm in diameter and length, light output is increased by a factor of 6.2 in collimation direction, while the emission half-angle is reduced by 50%. We measure excellent form fidelity and irradiance patterns close to simulation. Additionally, a more complex shape design is presented, which exhibits a nonconventional triangular illumination pattern. The introduced method features exceptional design freedoms which can be used to tailor high-quality miniature illumination optics for specific lighting tasks, for example, endoscopy.

Single Quantum Dot with Microlens and 3D-Printed Micro-objective as Integrated Bright Single-Photon Source

Integrated single-photon sources with high photon-extraction efficiency are key building blocks for applications in the field of quantum communications. We report on a bright single-photon source realized by on-chip integration of a deterministic quantum dot microlens with a 3D-printed multilens micro-objective. The device concept benefits from a sophisticated combination of in situ 3D electron-beam lithography to realize the quantum dot microlens and 3D femtosecond direct laser writing for creation of the micro-objective. In this way, we obtain a high-quality quantum device with broadband photon-extraction efficiency of (40 ± 4)% and high suppression of multiphoton emission events with g(2)(τ = 0) < 0.02. Our results highlight the opportunities that arise from tailoring the optical properties of quantum emitters using integrated optics with high potential for the further development of plug-and-play fiber-coupled single-photon sources.

Wave-optical design of a combined refractive-diffractive varifocal lens

A novel type of integrated refractive-diffractive varifocal membrane lens is designed and analyzed by wave-optical methods. In contrast to other hybrid devices, the diffractive microstructure is directly imprinted onto the soft deflecting membrane, allowing for a high level of integration. Elastic deformation is taken into account by mechanical simulations with the finite element method (FEM). We show, that the superimposed structure can considerably suppress chromatic and spherical aberration. Furthermore, our algorithm is successfully applied to design a confocal hyperspectral lens.

Rotationally symmetric formulation of the wave propagation method-application to the straylight analysis of diffractive lenses

We introduce a modified formulation of the wave propagation method for the efficient simulation of rotationally symmetric micro-optical components. The reformulated algorithm provides an increased computational performance of approximately two orders of magnitude and strongly reduced memory requirements, in comparison to the original formulation. This enables the efficient wave optical simulation of extended micro-optical structures beyond the common thin-element approximation. As a prototypical example, we assess the modified algorithm for the evaluation of straylight induced by diffractive lenses. We find an excellent accuracy, while comparing to rigorous simulations, which justifies the ability to overcome the limitations of the thin-element approximation.

Single mode fiber based delivery of OAM light by 3D direct laser writing

We demonstrate orbital-angular momentum (OAM) light up to a topological charge of l=3 behind a single mode fiber. Femtosecond 3D direct laser writing is used to fabricate spiral phase plates of l=1,2 and 3, composed of 10 discrete steps, on the tip of single mode optical fibers. These structures efficiently convert out-coupled light from the fiber at 785 nm wavelength into optical vortex beams carrying an orbital-angular momentum of lℏper photon. Far field intensity patterns and interferograms of the OAM beams are recorded using a CCD camera. The results are in excellent agreement with numerical simulations obtained from the wave propagation method.

Design, simulation and 3D printing of complex micro-optics for imaging

In this work we use a hybrid geometrical and wave-optical approach to design and simulate stacked microlenses with varying fields of view. After 3D printing, an excellent agreement of simulated and measured imaging performance is found.

Micro objectives with extremely large field of view

In this paper, we compare a standard wide angle system design to an array of four off-axis micro optics systems. The reference system is a single x/y-symmetric optical system to reach full field of view (FOV) of 140°×170°. To obtain the same FOV an array of four off-axis systems, consisting of tilted and decentered freeform elements, with small sub FOVs is designed. The system design is such that a production via 3D-two-photon printing is possible. We compare the performances of the standard system to that of the array of off-axis systems.

Compact see-through AR system using buried imaging fiber bundles

This design concept is using multi-core imaging fiber bundles with small diameters (<350 μm) to transfer information from an image source (e.g. laser pico projector) to the eye of the user. One of the main benefits of this approach is that the resulting glasses are almost indistinguishable from conventional eyewear. Not only are the fiber bundles very thin and positioned close to the eye but their difference in refractive index compared to the surrounding medium is comparably small which makes them hardly visible. At the same time, they can carry a significant space-bandwidth product and may be easier to fabricate in comparison to similar solutions using waveguides or Fresnel-type extractors. Using ray tracing and wave-optical considerations, we show that such an approach can lead to highly inconspicuous AR glasses with a >20° diagonal field of view and good angular resolution.