Additive Manufacturing of Micro-Optics
Nanoscribe enables 3D printing of micro-optics
Eggenstein-Leopoldshafen The German company Nanoscribe is developing and producing high-precision 3D printing solutions enabling the micro-optics industry to innovate by additive manufacturing. Typically, the benefits of additive manufacturing are considered to be fast and flexible design iterations as well as freedom of design. But the usual 3D printing technologies available in the market fail to meet the resolution and precision requirements of optical applications.
However, a broad range of almost arbitrary micro-optical shapes including standard refractive micro-optics, freeform optics, diffractive optical elements or even multiplet lens systems can now be printed in a one step-process by means of Nanoscribe´s Photonic Professional GT 3D printers, tailored solutions and materials. The additive manufacturing approach allows to directly fabricate micro-optical components from polymers with optically smooth surfaces, high shape accuracy and significantly smaller geometrical and design constraints than standard fabrication methods. The additive manufacturing workflow also drastically shortens the design-iteration phase and ideas can be turned into functional prototypes within just a few days.
Nanoscribe closes the gap between 3D printing and micro-optics with this flexible tool enabling unprecedented applications in micro-optics.
Examples of micro-optics fabricated by 3D printing:
The freedom of design provided by 3D printing also implies that almost any concave or convex or entirely freeform surface shape can be fabricated with this technique. Recently, e.g., researchers from the University of Stuttgart (Germany) directly 3D printed doublet lens systems onto CMOS image sensors thereby creating a high-performance and compact imaging system. Not only the optical performance is impressive, but the design iteration process was drastically accelerated. It took less than a day to implement new designs from the idea to the final part.
A further outstanding structure demonstrating the high shape accuracy and optically smooth surfaces achievable by using this technology are the hemispherical micro lenses (right). They have a shape accuracy better than 1 µm and a surface roughness better than 10 nm Ra. The array with a size of 1 square centimeter in total and semispheres with a height of 150 µm was written into a solid negative tone resist. Due to the optimized combination of hardware and software components one can achieve a high and consistent precision on the whole area of the writing field. Micro-optical components on wafer-level can be fabricated by the same technology.
Using a Nanoscribe system, the fabrication of diffractive optical elements (DOE) which typically have significantly smaller feature sizes than refractive optics, is possible as well. DOEs can be designed for functionalities that are hardly accessible with refractive optics, such as the generation of almost arbitrary light distributions in the far-field. By means of a Photonic Professional GT, functional multilayered diffractive optical elements can be directly patterned onto glass substrates enabling rapid protoyping and design iterations within a few days.
Photonic Professional GT
Nanoscribe’s 3D printer Photonic Professional GT are based on the technique of two-photon polymerization and allow for additive manufacturing with world-record resolution. Feature sizes and line spacings down to 200 nm and 500 nm, respectively, as well as optical quality surface finishes are characteristic key features. In 3D, the system offers a 100x higher resolution than stereolithography whereas in 2.5D it offers a design freedom and structural heights far beyond grey scale lithography and diamond machining. Even for traditional 2D maskless lithography it has proven to be an indispensable tool providing feature sizes and a resolution otherwise only achievable with electron beam lithography and in addition extraordinarily high aspect ratios. The system is fully embedded in a typical 3D printing workflow and offers the ease of use known from conventional 3D printing. Nanoscribe also supplies a special product line-up of photopolymers tailored to its printer. Each of these easy-to-use resins maximizes a different quality criterion such as resolution, surface smoothness, throughput, etc. With the Photonic Professional GT, these materials or other, industrial UV-curable resins can be processed either additively or, in some cases, subtractively on a broad range of substrates. A lot of these polymers are compatible with typical electroplating and gas-phase deposition processes, allowing the printed parts to be coated or transferred into other materials such as gold, nickel, copper (and alloys thereof) as well as silicon or titanium dioxide. Fast and low cost production can therefore also be addressed, e.g. by fabricating a nickel shim from the printed polymer structures by electroforming. This allows cheap and standard mass replication techniques such as injection molding or hot embossing to be used. Replication using nanoimprinting is another viable route.
Founded in 2007 as a spin-off from the Karlsruhe Institute of Technology, Germany, and as a pioneer in the field of two-photon polymerization, Nanoscribe has established itself globally as the market and technology leader in 3D printing on the nano-, micro- and mesoscale. Today it is ranked among the most successful young medium-sized companies in Germany. Top institutions in academia as well as pioneers in industry in more than 30 countries worldwide already successfully use this new, award-winning standard for microfabrication. On our website, you can find a multitude of examples for the broad range of applications as well as a long list of scientific papers published by our users. www.nanoscribe.com
Image 1: Photonic Professional GT: 3D printer for the fabrication of micro-optics
Image 2: Regular arrangement of doublet lenses directly fabricated on a CMOS image sensor (University of Stuttgart)
Image 3: Array of semisphere micro-optics fabricated with a Photonic Professional GT.
Image 4: Diffraction pattern from a polymer diffractive optical element fabricated with a Photonic Professional GT.