We employ aligned two-photon lithography (A2PL®), to push high precision alignment tasks from the photonic packaging step towards the fabrication process in a one step process. Combined with Two-Photon Grayscale Lithography (2GL®), this approach enables direct fabrication of micro-optical elements onto devices, enhancing functionality with highest surface quality and shape fidelity at high throughput. We demonstrate automated 3D alignment using customer-ready detection algorithms, to fabricate micro-optical elements attached to various topographies and material platforms with exceptional accuracy below 100 nm. We showcase micro-optical elements aligned to fiber tips, photonic edge couplers, and photonic grating couplers to demonstrate the validity of A2PL for improved coupling losses and beam quality.
KEYWORDS: Printing, Two photon polymerization, Standards development, 3D microstructuring, Microfluidics, Microfabrication, In vivo imaging, Biomedical applications, Artificial intelligence, Tissue engineering
Herein, we demonstrate the translation of Two-Photon Grayscale Lithography (2GL®), as well as Aligned 2-Photon Lithography (A2PL®), to biomedical applications. Specifically, we will present a novel workflow of aligned two-photon polymerization (2PP) microfabrication for 3D cell assays and perfusion inside microfluidic devices. For completeness, we also reveal how 2GL® can be applied to artificial intelligence (AI) generated topographies for enhanced and scalable 2.5D cell culturing. The versatility offered by both aligned and 2GL® printing holds great promise for various applications in biotechnology, tissue engineering, and microfluidics, creating new opportunities for innovation within established biomedical and pharmaceutical industries.
We report on the progress of our efforts to apply silicon nitride photonic integrated circuits (PIC) to the miniaturization of optical coherence tomography (OCT) with the goal of facilitating its widespread use in ophthalmology at the point of care. In particular, we highlight the design and optical characterization of photonic building blocks allowing the realization of a silicon nitride PIC-based multi-channel swept-source OCT system in the 1060 nm wavelength region. Apart from waveguide structures, these building blocks include 3D-printed microlenses on the PIC end facets for efficient light coupling to and from the PIC.
Two-photon induced 3D laser lithography is a widely used technique in additive manufacturing of three-dimensional micro- and nanostructures. However, efficient two-photon absorption (2PA) comes at a cost: It requires femtosecond pulsed laser sources leading to large and expensive setups. Recently, we introduced two-step absorption (2SA) as a novel alternative excitation mechanism[1]. This allows for employing low-power continuous-wave light sources like inexpensive, compact semiconductor laser diodes for excitation. Here, we present a compact setup based on 2SA drastically reduced in cost and size showing the potential in the field of 3D laser lithography.
[1] Vincent Hahn, Tobias Messer, N. Maximilian Bojanowski, Ernest Ronald Curticean, Irene Wacker, Rasmus R. Schröder, Eva Blasco, and Martin Wegener, Nat. Photon. 15, 932-938 (2021)
We present recent advancements in two-photon grayscale lithography (2GL®). In contrast to one-photon grayscale lithography, for 2GL®, the exposed volume pixel is strongly confined to the vicinity of the laser focus allowing for a truly 3-dimensional dose control with very high spatial resolution. Discrete and accurate steps as well as essentially continuous topographies can be printed with increased throughput, on any substrate, and without the need for additional lithography steps or mask fabrication. We update on throughput and quality levels of the method. As demonstrators we fabricate and characterize a variety of microoptics and other benchmark structures.
We present recent advancements in two-photon grayscale lithography (2GL®). In contrast to one-photon grayscale lithography, for 2GL®, the exposed volume pixel is strongly confined to the vicinity of the laser focus allowing for a truly 3-dimensional dose control with very high spatial resolution. Discrete and accurate steps, as well as essentially continuous topographies, can be printed with increased throughput, on any substrate, and without the need for additional lithography steps or mask fabrication. We update on throughput and quality levels of the method. As demonstrators, we fabricate and characterize optics masters for replication technologies like nanoimprint lithography.
In this invited presentation we introduce aligned multiphoton lithography (AML®). In contrast to traditional mask(less) aligners based on one-photon lithography, in AML®, 3-dimensional shapes can be generated and aligned to 3-dimensional topographies. The unique resolution and design freedom of AML® opens new horizons for optical applications, hybrid photonic integration, MEMS, medicine, or life science applications. In this session we present the design and fabrication of micro-optical elements aligned to fiber tips, chip edge couplers, and laser output facets. The characterization of these elements is in very good agreement with simulations allowing us to also present experiments demonstrating low-loss coupling between the elements.
Direct imaging instruments have the spatial resolution to resolve exoplanets from their host star. This enables direct characterization of the exoplanets atmosphere, but most direct imaging instruments do not have spectrographs with high enough resolving power for detailed atmospheric characterization. We investigate the use of a single-mode diffraction-limited integral-field unit that is compact and easy to integrate into current and future direct imaging instruments for exoplanet characterization. This achieved by making use of recent progress in photonic manufacturing to create a single-mode fiber-fed image reformatter. The fiber link is created with three-dimensional printed lenses on top of a single-mode multicore fiber that feeds an ultrafast laser inscribed photonic chip that reformats the fiber into a pseudoslit. We then couple it to a first-order spectrograph with a triple stacked volume phase holographic grating for a high efficiency over a large bandwidth. The prototype system has had a successful first-light observing run at the 4.2-m William Herschel Telescope. The measured on-sky resolving power is between 2500 and 3000, depending on the wavelength. With our observations, we show that single-mode integral-field spectroscopy is a viable option for current and future exoplanet imaging instruments.
In the new era of Extremely Large Telescopes (ELTs) currently under construction, challenging requirements drive spectrograph designs towards techniques that efficiently use a facility's light collection power. Operating in the single-mode (SM) regime, close to the diffraction limit, reduces the footprint of the instrument compared to a conventional high-resolving power spectrograph. The custom built injection fiber system with 3D-printed microlenses on top of it for the replicable high-resolution exoplanet and asteroseismology spectrograph (RHEA) at Subaru in combination with extreme adaptive optics of SCExAO, proved its high efficiency in a lab environment, manifesting up to ~77% of the theoretical predicted performance.
The Multi-Core Integral-Field Unit (MCIFU) is a new diffraction-limited near-infrared integral-field unit for exoplanet atmosphere characterization with extreme adaptive optics (xAO) instruments. It has been developed as an experimental pathfinder for spectroscopic upgrades for SPHERE+/VLT and other xAO systems. The wavelength range covers 1.0 um to 1.6um at a resolving power around 5000 for 73 points on-sky. The MCIFU uses novel astrophotonic components to make this very compact and robust spectrograph. We performed the first successful on-sky test with CANARY at the 4.2 meter William Herschel Telescope in July 2019, where observed standard stars and several stellar binaries. An improved version of the MCIFU will be used with MagAO-X, the new extreme adaptive optics system at the 6.5 meter Magellan Clay telescope in Chile. We will show and discuss the first-light performance and operations of the MCIFU at CANARY and discuss the integration of the MCIFU with MagAO-X.
The Multi-Core Integral-Field Unit (MCIFU) is a diffraction-limited near-infrared integral-field spectrograph designed to detect and characterise exoplanets and disks in combination with extreme adaptive optics (xAO) instruments. It has been developed by an extended consortium as an experimental path finder for medium resolution spectroscopic upgrades for xAO systems. To allow it to achieve its goals we manufactured a fibre link system composed of a custom integrated fiber, with 3D printed microlenses and an ultrafast laser inscribed reformatter. Here we detail the specific requirements of the fibre link, from its design parameters, through its manufacture the laboratory performance and discuss upgrades for the future.
Confocal laser endomicroscopy (CLE) has found an increasing number of applications in clinical and pre-clinical studies, for it allows intraoperative in-situ tissue morphology at cellular resolution. CLE is considered as one of the most promising systems for in-vivo pathological diagnostics. Miniaturized imaging probes are designed for intraoperative applications. Due to less sophisticated optical design, CLE systems are more prone to image aberrations and distortions. While diagnostics with CLE takes reference from the corresponding histological images, the determination of the resolution and aberrations of the CLE systems becomes essential. Thereby on-site quality check of system performance is required. Additionally, these compact systems enable a field of view of less than half square millimeter without zooming function, which makes it difficult to correlate human vision to the microscopic scenes. Therefore, it is necessary to have defined microstructures working as a test target for CLE systems. We have extended the 2D bar pattern in 1951 USAF test chart to 3D structures for both lateral and axial resolution assessment, since axial resolution represents the optical sectioning ability of CLE systems and is one of the key parameters to be assessed. The test target was produced by direct laser writing. Yellow-green fluorescence emission can be excited at 488 nm. It can also be used for other fluorescence microscopic imaging modalities in the corresponding wavelength range.
We introduce a design for a tip-tilt sensor with integrated single-mode fiber coupling for use with the front-end prototype of the iLocater spectrograph at the Large Binocular Telescope to detect vibrations that occur within the optical train. This sensor is made up of a micro-lens array printed on top of a fiber bundle consisting of a central single-mode fiber and six surrounding multi-mode fibers. The design in based on a previous prototype that utilized a multi-core fiber with seven single-mode fibers.1 With this updated design, we are able to achieve a better sensing throughput. We report on the modeled performance: if the beam is perfectly aligned, 69% light is coupled into the central single-mode fiber feeding the scientific instrument. When the beam is not aligned, some of the light will be coupled into the outer sensing fibers, providing the position of the beam for tip-tilt correction. For this design we show that there is a linear response in the sensing fibers when the beam is subject to tip-tilt movement. Furthermore we introduce an adaptive optics testbed, which we call the Koenigstuhl Observatory Opto-mechatronics Laboratory (KOOL), this testbed currently simulates vibrations at the Large Binocular Telescope, and in collaboration we have extended it to allow single-mode fiber coupling tests.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.