Application Examples

Multiphoton Optics’ processes are employed to create products in the fields of photonics, biomedicine, life sciences, and functional materials by using our high-precision 3D printer LithoProf3D. For all product categories, scalability of the processes and of the accessible feature sizes is required. The fabrication is individually adapted to the structural requirements, whereas a large variety of fabrication modes and exposure trajectories can be selected in our software product LithoSoft3D®.

The technology’s appeal is an intrinsic scalability from the 100 nm to the cm regime. The capability of the TPA process to be extended from the sub-µm scale to the macro scale was already demonstrated beginning in 2001 in a series of different publicly funded projects to evaluate the technology for industrial scale fabrication by Multiphoton Optics’ CEO and partners. In 2009, the first macro bodies of about 8 mm and 2 cm in size, and – at the same time – the possibility to work on a sub-µm scale, were created and presented at the Photonics West exhibition in 2009, with an adapted re-design file to decrease the fabrication time.

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Connect the world – create optical connectivity on demand at low cost

The amount of data nowadays being transported has reached continuously increasing volumes, driven by big data applications, Internet of Things (IoT), and Industry 4.0. The requirement of being connected in business and on consumer level has led to a tremendous socio-economic impact. Around the globe, large corporations operate data centers to provide distributed computing and redundant storage across continents. These data centers require power at megawatt levels, and they often have their own power supplies, redundant fail-safe power backup, and independent cooling. As revealed from considerations of the power usage efficiency (PUE), about 50 to 60 % of power consumption are attributed to the server component level such as processors, memories, and storage devices, while the rest of the power is consumed by support systems such as power supplies, power distribution systems, cooling systems, building entrance switchgear, and medium voltage transformer. For each single Watt saved at the server component level, an additional saving of more than 1.8 Watts is achieved. Thus, reducing power consumption on the processing side will trigger a cascade effect that further contributes to the reduction of power consumption. However, reduction of energy in data transfer systems is one of the key figures which not only affects data centers, but which also has significant impact on all data processing systems in a vast majority of products.

Optical Interconnects

A way of decreasing energy consumption in data transfer systems is to substitute part of the electrical connections by optical interconnects (OI) (sometimes called optical links or, misleadingly, optical “wire bonds”). The creation of OI has been addressed in the past two decades, and many different technologies have been explored for their manufacturing. Most of the technologies considered so far will be hard to be scaled to volume manufacturing, particularly when considering components requiring single-mode waveguides. The main reason for that is the required precision of way less than a micron of the alignment of the optical components to the waveguides. While state-of-the-art assembly equipment can handle substrates and dies, they will be far too slow when a sub-micron precision is required. This, however, is critical for scaling to large volumes of a product. Aside of that, an alignment of multiple I/Os from an optical arrangement such as from photonic integrated chips or lasers will be even harder than for a single I/O, if technical solutions are sought only on the waveguide manufacturing side.

Currently, optical components are passively and actively aligned, and particularly for the latter the device needs to be powered up to emit or receive light like in live operation. While active alignment is common practice, to use just passive alignment would be the preferred choice, since this saves a vast amount of time and is easier to implement. The creation of optical waveguides is only a part of the tasks to be solved to fabricate a complete optical interconnect, and additional features such as, for example, drivers, E/O and O/E conversion, light source detectors and amplifiers. All these elements along with the waveguide have to be included to account for the complete system to deliver an added value to the final product

Focal scan in z direction of a pitch adaptation.

Microoptical Components

Due its maskless 3D technology, Multiphoton Optics’ two-photon absorption (TPA) process enables the generation of refractive and diffractive microoptical elements with arbitrary shapes in an arbitrary arrangement on a large variety of substrates.

This unlimited freedom of design is a unique feature compared to conventional techniques, and it thus provides the solution for novel device architectures in order to cope with the increasing demand of creating miniaturized devices with multiple functions.

There are two scenarios to employ the technology in microlens fabrication. Individual microlenses or microlens arrays can be fabricated using LithoProf3D directly on photonic chips or on substrates to be implemented in endoscopic devices for in- and outcoupling purposes. These microlenses can be fabricated by our technology with a surface roughness of 2 to 4 nm, way below the critical value of λ/10 (with λ being the operation wavelength of the device). Thus, microlenses or microlens arrays for devices operating in the IR down to the VIS and the UV range can be created. Aside of this, replication masters can be manufactured, providing mass production capabilities of sophisticated optical designs.

Single microoptical devices, arrays, or even combinations of differently shaped microlenses providing specially designed, novel imaging properties can be conveniently fabricated by LithoProf3D. These lenses or lens arrays are, for example, very useful for imaging and sensor products in all kind of application scenarios, where these sensor and imaging products are employed.

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Spherical microlens array.

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Array with donut-shaped microlenses.

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Array with spherical microlens on a cylindrical base.

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Fresnel lense array.

Master Fabrication

Parallelization via replication of master structures provides a basis for increasing throughput and decreasing fabrication costs at the same time. With our key technology, arbitrarily shaped 3D master structures like individual microlenses of the same or of arbitrarily arranged shapes can be generated. Aside of microlenses, structures suitable for nanoimprint lithography jobs can be individually fabricated with the same approach, making use of the technology’s scalability from the 100 nm to the macro regime. These structures are then used to create a replication tool which then is be used to replicate the master structure on different substrates for a large variety of structure dimensions.

Material Research

The introduction of novel materials into a manufacturing environment often requires special attention. Although many materials are known to be patternable in two dimensions by conventional 2D methods like, for example, UV lithography or replication technologies, their capability of being processed in 3D with highest precision is still not known in most cases. Thus, this has to be individually investigated, and the ability to be structured by 3D methods needs to be evaluated. The high-precision 3D printer LithoProf3D is perfectly suited to fulfill this task, since it allows the fast and reliable investigation of the patternability of novel materials using automated parameter search routines in LithoSoft3D® with very simple or more sophisticated test structures arranged in parameter variation fields.

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Woodpile parameter search array in a novel material. From left to right: variation of writing velocity, from top to bottom: variation of applied laser power.

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Woodpile array with adjustable layer orientation.

Biomedical and Life Science Applications

Aside from photonic products, the technology is also suited for the fabrication of structures for biomedical products or life science applications. Scaffolds and specially shaped surface structures or functions can be additively and subtractively created which are useful in Tissue Engineering applications. Other applications are in drug delivery systems or in microfluidics.

Tissue Engineering

Scaffolds in 3D mimicking particular geometries are fabricated fast and reliably up to very large scales using Multiphoton Optics’ unique technology and equipment features. For the restoration of diseased or damaged tissue, the growth of cells on 3D porous scaffolds for tissue engineering is a promising approach to generate autologous tissue. Structure type and size can be simply varied to investigate their influence on primary human microvascular endothelial cells.

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SPP1327 (Heike Walles, Tissue Engineering & Regenerative Medicine (TERM), University Hospital Würzburg), and Ruth Houbertz (formerly Fraunhofer ISC, Würzburg)