Analysis of assembly tolerance compensation in microscope objectives with a free-form element at the aperture stop.

We analyze the feasibility of using refractive free-form phase plates at the aperture stop of microscope objectives as an alternative to active alignment to compensate for assembly tolerances. The method involves the determination of misalignment-induced aberrations at the exit pupil, and transferring them to the aperture stop while taking pupil aberrations into consideration. We demonstrate that despite being able to correct only for field-independent aberrations, this method can restore near-diffraction-limited imaging performance of passively aligned systems with practical tolerances, given that the as-designed system is highly corrected. We confirm the results via numerical simulations for two different commercial objective designs.

Fully refractive adaptive optics fluorescence microscope using an optofluidic wavefront modulator.

Adaptive optics (AO) represents a powerful range of image correction technologies with proven benefits for many life-science microscopy methods. However, the complexity of adding a reflective wavefront modulator and in some cases a wavefront sensor into an already complicated microscope has made AO prohibitive for its widespread adaptation in microscopy systems. We present here the design and performance of a compact fluorescence microscope using a fully refractive optofluidic wavefront modulator, yielding imaging performance on par with that of conventional deformable mirrors, both in correction fidelity and articulation. We combine this device with a modal sensorless wavefront estimation algorithm that uses spatial frequency content of acquired images as a quality metric and thereby demonstrate a completely in-line adaptive optics microscope that can perform aberration correction up to 4th radial order of Zernike modes. This entirely new concept for adaptive optics microscopy may prove to extend the performance limits and widespread applicability of AO in life-science imaging.

Extended field-of-view adaptive optics in microscopy via numerical field segmentation.

Sample-induced optical aberrations in microscopy are, in general, field dependent, limiting their correction via pupil adaptive optics (AO) to the center of the available field-of-view (FoV). This is a major hindrance, particularly for deep tissue imaging, where AO has a significant impact. We present a new wide-field AO microscopy scheme, in which the deformable element is located at the pupil plane of the objective. To maintain high-quality correction across its entirety, the FoV is partitioned into small segments, and a separate aberration estimation is performed for each via a modal-decomposition-based indirect wavefront sensing algorithm. A final full-field image is synthesized by stitching of the partitions corrected consecutively and independently via their respective measured aberrations. The performance and limitations of the method are experimentally explored on synthetic samples imaged via a custom-developed AO fluorescence microscope featuring an optofluidic refractive wavefront modulator.

Reusable thin-film all-polymer couplers for vertical light coupling to single-mode waveguides.

A reusable all-polymer coupler using gratings and tapers for vertical light coupling to single-mode planar waveguides is demonstrated. Numerical simulations are performed to optimize the tapers and gratings to increase the coupling efficiency. A hot-embossing replication technique is used for the fabrication of waveguide sensors and gratings, which is adaptable to mass production, such as roll-to-roll processes. The external grating is reversibly bonded to the waveguide via van der Waals forces, and the thus realized re-usability reduces the fabrication costs. The utility of the structure is shown by using these grating couplers for testing of asymmetric Mach-Zehnder interferometers.

Injection Molding of Magnesium Aluminate Spinel Nanocomposites for High-Throughput Manufacturing of Transparent Ceramics.

Transparent ceramics like magnesium aluminate spinel (MAS) are considered the next step in material evolution showing unmatched mechanical, chemical and physical resistance combined with high optical transparency. Unfortunately, transparent ceramics are notoriously difficult to shape, especially on the microscale. Therefore, a thermoplastic MAS nanocomposite is developed that can be shaped by polymer injection molding at high speed and precision. The nanocomposite is converted to dense MAS by debinding, pre-sintering, and hot isostatic pressing yielding transparent ceramics with high optical transmission up to 84 % and high mechanical strength. A transparent macroscopic MAS components with wall thicknesses up to 4 mm as well as microstructured components with single micrometer resolution are shown. This work makes transparent MAS ceramics accessible to modern high-throughput polymer processing techniques for fast and cost-efficient manufacturing of macroscopic and microstructured components enabling a plethora of potential applications from optics and photonics, medicine to scratch and break-resistant transparent windows for consumer electronics.

High-throughput injection molding of transparent fused silica glass.

Glass is one of the most relevant high-performance materials that has the benefit of a favorable environmental footprint compared with that of other commodity materials. Despite the advantageous properties of glasses, polymers are often favored because they can be processed using scalable industrial replication techniques like injection molding (IM). Glasses are generally processed through melting, which is both energy intensive and technologically challenging. We present a process for glassworks using high-throughput IM of an amorphous silicon dioxide nanocomposite that combines established process technologies and low-energy sintering. We produce highly transparent glass using classical IM and sintering, allowing for a potentially substantial reduction in energy consumption. Our strategy merges polymer and glass processing, with substantial implications for glass utilization.