Current lens systems are restricted in size, shape and dimensions by limitations of manufacturing. Multi-lens elements with non-spherical shapes are required for high optical performance and to correct for aberrations when imaging at wide angles and large fields. Here we present a novel concept in optics that overcomes all of the aforementioned difficulties and opens the new field of 3D printed micro-and nano-optics with complex lens designs. We demonstrate the complete process chain, from optical design, manufacturing by femtosecond two-photon direct laser writing and testing to the application of multi-lens objectives with sizes around 100 µm, and validate their high performance and functionality by quantitative measurements of the modulation transfer function and aberrations. The unprecedented flexibility of our method paves the way towards printed optical miniature instruments such as endoscopes, fibre-imaging systems for cell biology, new illumination systems, miniature optical fibre traps, integrated quantum emitters and detectors, and miniature drones and robots with autonomous vision.A dditive manufacturing enables new and unprecedented engineering and production possibilities that are predicted to have an enormous impact in the twenty-first century. The technology allows for the simple three-dimensional (3D) printing of volumetric objects directly from a computer-aided design 1 . So far, additively manufactured objects are mostly fabricated from metals, ceramics and opaque plastics. There are a number of different fabrication methods to manufacture small and high-performance micro-optical systems 2-10 ; however, these technologies suffer from drawbacks such as limited miniaturization, inability to combine multiple elements, restrictions in designing the surfaces 2-4,11 and problems with the alignment 12 .Multiphoton lithography is one of various 3D printing technologies that realize the fabrication of 3D objects 13-15 . Using femtosecond laser pulses and two-photon absorption, this manufacturing method takes 3D printing down to submicrometre feature sizes and therefore pushes the ongoing trend of miniaturization forwards. Direct laser writing with highly transparent photoresists enables 3D printing to enter the realm of manufacturing optical elements at the micro-and nanometre scale [16][17][18][19][20][21][22] . Thus the precise fabrication of complex optical elements on demand becomes possible.We demonstrate that 3D direct laser writing is a suitable tool for fabricating complex multi-lens optical systems that show high optical performances and tremendous compactness. Until now multi-lens optics that have comparable performances are considerably larger 12,23 and at the same time do not show the manifold compound structures and possibilities presented here. Our optical devices consist of several different free-form lens elements with air in between. This work is right at the interface between microand nano-optics and represents a paradigm shift for micro-optics. It takes only a few hours from lens desig...

Liquid-filled photonic crystal fibers and optofluidic devices require infiltration with a variety of liquids whose linear optical properties are still not well known over a broad spectral range, particularly in the near infrared. Hence, dispersion and absorption properties in the visible and near-infrared wavelength region have been determined for distilled water, heavy water, chloroform, carbon tetrachloride, toluene, ethanol, carbon disulfide, and nitrobenzene at a temperature of 20°C. For the refractive index measurement a standard Abbe refractometer in combination with a white light laser and a technique to calculate correction terms to compensate for the dispersion of the glass prism has been used. New refractive index data and derived dispersion formulas between a wavelength of 500 nm and 1600 nm are presented in good agreement with sparsely existing reference data in this wavelength range. The absorption coefficient has been deduced from the difference of the losses of several identically prepared liquid filled glass cells or tubes of different lengths. We present absorption data in the wavelength region between 500 nm and 1750 nm.

No abstract

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.

A highly miniaturized vision system is realized by directly 3D-printing different multilens objectives onto a CMOS image sensor.