New optical materials as well as efficient light sources are the basis for optical systems design. The term “Optical Materials and Systems” is meant to include systems for the generation of light like lasers, LEDs or OLEDs, for the conversion of light as photonic crystal fibers and classical optical systems and micro- and nano-optical materials and systems, in which light is controlled and transported. The advancing possibilities to create tailor-made materials with structures on the wavelength and sub-wavelength scale has promoted the development of optical materials and elements with desired optical functionality. The topics within this thematic priority span a wide range from more physics-driven basic research, i.e. understanding and designing new materials, to the engineering sciences with applications of these new materials and systems.

The different participating institutes cover a large range of these topics from basic developments to applications. This thematic priority are divided into several modules, both in research and in teaching

Advanced Laser Design. Fiber lasers and disk lasers have recently attracted much attention due to their high output power and excellent beam quality. Especially non-linear optical effects in such lasers will be investigated. For example, Raman fiber lasers can generate light at wavelengths which cannot easily be obtained by conventional solid-state lasers but are very promising for medical applications. Careful numerical analysis and design of such lasers as well as experimental investigations with new types of fibers will be performed in order to optimize e.g. spectral properties of generated light. Fiber-Bragg Gratings (FBGs) acting as micro-mirrors machined directly into optical fibers are key components in fiber lasers. Sophisticated FBGs with special and tunable spectral properties will also be studied closely. Different types of photonic crystal fibres (PCF) will be further optimize for light conversion and super continuum generation. Gas-filled hollow core will be used as new light sources in using the hollow core as a very small laser tube for e.g. a HeNe or HeCd laser, but also by higher harmonic generation PCF filled with noble gases. For use in high precision metrology, ultra-stable lasers, i.e. with a stabilization on the sub-Hz level will be developed.

New optical materials. Classical optics was always limited to the use of a few transparent materials. New optical materials are conventional substances with subwavelength-structures, designed in a way to induce new optical properties, e.g. extreme refractive indices, extremely low velocity of light, high birefringence. Two groups of structures are being focused on, both having received considerable attention in recent years. The first group includes photonic crystal fibers, in short PCF, i.e. optical fibers with a lateral structure. These two-dimensional crystals offer possibilities to fabricate fibers for specific purposes with tailor-made characteristics, but also serve as a model system to observe chemical reactions or light-matter interactions in confined space, but with a sufficiently long interaction length. While the basic principles have been clarified in the past years, a wide variety of applications of PCF in e.g. telecommunications, metrology, chemical and biochemical sensing, are being currently explored. PCF from other materials, e.g. soft glasses, that guide light in the infrared and are thus potential candidates for the use in optical material processing, are currently under investigation and will be further optimized towards applications. The voids of PCFs will be filled with metals to create new types of plasmonic filters.

The second group of optical materials includes 3-dimensional effective materials with structures in the subwavelength and nanometer-regime, as photonic crystals and so-called metamaterials. Some progress has already been obtained with respect to the self-assembly of colloidal particles in regular lattices thus forming resonant structures. In the next funding period those opals will be combined with metallic structures to generate mixed states of plasmons and Bloch modes and to extend the capability of photonic crystals towards sensing and light harvesting in solar cells. With the availability of advanced structuring techniques the field of metamaterials has received increasing interest. Fundamental effects as negative refraction and super resolution imaging could be demonstrated in the microwave domain and now those results are about to be transferred to the optical region. Using lithographic methods effective optical materials will be generated from metallic films and investigated optically. An alternative approach is to tailor and assemble organic macromolecules as carbon nanotubes to obtain a suitable magnetic or dielectric response in the optical domain. Research and teaching has already profited from the installation of microstructuring and fibre drawing equipment in Erlangen. An even deeper involvement of students into these new technologies is planned for the next funding period.

Micro-optical elements and their applications. Diffractive as well as refractive elements have numerous applications, e.g. in beam shaping, interferometry or as a wave front sensor. Especially absolute interferometric tests of large surfaces, e.g. aspherics or cylinders, can be performed. While binary structures are quite commonly used, grey tone lithography is a sophisticated technique. However, there is quite some experience in Erlangen using it, e.g. for the production of microlens arrays that can be used as highly sensitive wave front sensors. The design of the micro-optical element needed for a specific application often requires simulation techniques, as described in the computational optics module. In addition we will apply new analytical techniques as so-called transformation optics to generate new optical designs by transforming already known systems. The technology of producing all kinds of elements is available in Erlangen. Thus the whole range from design to application can be covered.

Polarization-optimized systems. Up to now polarization as an optimizing factor in optical systems has been rather neglected. However, experiments with systems with a high numerical aperture have shown quite early that a TEM00 laser mode does not exhibit the theoretical minimum focal spot and is also distorted in shape. Recently it has been shown that certain polarization patterns, which seem at first sight complicated, offer superior optical performance, e.g. a smaller focal spot. These results have potential applications in optical data storage, microscopy and lithography. Another interesting feature of radial polarization, being one example for a specific polarization pattern, is the existence of a considerable longitudinal component of the electrical field at the focus. This component can be used to couple to small structures like quantum wells or quantum dots. In particular the application of polarization tailored beams in combination with advanced recording schemes and with a clever numerical evaluation allows for a detailed investigation and characterization of optical nanostructures with sub-wavelength resolution. Those schemes will be extended towards a polarization sensitive scanning microscopy with subwavelength resolution.

THz Photonics. The Terahertz (THz) or far-infrared spectral region is attractive for possible applications in biomedical studies, as “fingerprints” for bio-molecules or for remote sensing and imaging. During the last funding period considerable progress has been obtained in the development of a room temperature CW-THz source using a photo-mixing technique. Now stable and reliable continuous wave THz sources are available and will be used to characterize materials also for that spectral range. Metamaterials originally developed for microwave applications will be optimized for the THz domain to create artificial dielectrics and micro-structured surfaces with novel spectral properties, for example as anti-reflection coatings and frequency-selective surfaces. Furthermore, advanced systems for metrology, sensing and imaging will be scrutinized.