The Max Planck School of Photonics (MPSP) provides and coordinates an integrated program for the photonics education of graduate and doctoral students in a network of excellence of German universities and research institutions. Students can choose to start the program with a qualification phase to obtain a photonics Master’s degree from one of three teaching universities in Erlangen, Jena or Karlsruhe. The subsequent PhD-phase lasts three years and the research work is conducted under the supervision of one out of 45 Fellows of the MPSP. Students already holding a qualifying Master’s degree can apply to directly enter the PhD-phase of the program. Apart from an excellent network of renowned scientists and research institutions, the MPSP offers generous financial support and a supporting curriculum to foster interactions between the different photonics disciplines, to strengthen the research network and to advance personal and professional skills. Maintaining and supporting active interactions of the MPSP research network at all levels is challenging and will be backed up by employing digital learning tools and platforms. Here, we will present our recent findings on chances and opportunities provided by the MPSP’s educative approach.
Metamaterials promise the possibility to tailor the propagation properties of light at the nano-scale. With this
contribution we explore the possibility to combine the concept of metamaterials with integrated optics.
We investigate a system consisting of a one-dimensional array of double cut-wires (two very thin gold sheets
separated by a dielectric spacer) placed on top of a dielectric slab waveguide, which supports only the fundamental
TE and TM mode in the near infrared spectral region around 1550 nm. Strong coupling of the waveguide modes
to the plasmonic eigenmodes of the double cut-wire is achieved via the longitudinal component of the electric
field, being relatively large for an asymmetric refractive index profile. By tuning the length of the double cutwires,
we can tune the spectral position of the occurring hybrid resonance. We will show by rigorous calculations,
that the resonance is anti-symmetric and hence produces artificial magnetism at optical frequencies in this simple
To further explore the physics of the system, we investigate the dispersion relation of a periodic array of
double cut-wires with varying lattice periods. The slab waveguide mode leads to a coupling of the individual
plasmonic nanostructures. We find that for short lattice periods the dispersion closely resembles that of the
slab waveguide. However when the Bragg frequency approaches the plasmonic resonance frequency, a strong
interaction takes place and leads to a back-bending of the dispersion relation with regions of negative group
velocity near to the band edge while an avoided crossing of both resonances takes place.
The different propagating modes in an optical fiber determine the properties of the light emerging the fiber.
Therefore an exact knowledge of the modal content is a key to understand the underlying physical effects. Different
approaches exist to measure the modal content of an optical fiber, such as interferometry, M<sup>2</sup> measurement
or phase retrieval methods with either high experimental complexity or ambiguity relating to the modal content.
In this paper we present a method for measuring the modal content by the aid of optical correlation analysis.
We demonstrate this with measurements on a passive step-index LMA fiber at a wavelength of 1064 nm.
Modal decomposition by means of correlation filters has been proved as a key for real online laser beam analysis.
To compare that method with the "standard" M<sup>2</sup> method, we generated series of different laser beams (1064 nm),
applied both methods to one and the same beam and evaluated achieved results. An adjustable Nd:YAG laser
served as transversal mode generator, delivering diverse "pure" Gauss-Hermite modes and superpositions of
modes, respectively. In the case of incoherent superposition of modes, their particular contribution to the
general M<sup>2</sup> value should be proportional to their relative strength, whereas in the case of coherent superposition
M<sup>2</sup> is distinctly influenced by phase differences between the discrete modal components. Achieved experimental
findings are well confirmed by computer simulation.
To qualify passive fibers for (high power) laser beam delivery, different experimental approaches (interferometric,
heterodyn, <i>M</i><sup>2</sup>, ...for beam characterization at fiber output are under test in the community. Measurement of
the individual strength of different components (eigenmodes) contained in the superposition at the fiber output
in dependence for example on bending radius seems to be very promising. This can be done by means of optical
correlation filters based on DOEs. For a standard telecommunication fiber SMF-28, operated at 633 nm, this
could be demonstrated earlier<sup>1</sup> by us. Here we present experimental results for quantitative proof of LP modes
in LMA fibers as well as in SMF-28 fibers by means of such correlation filters, and demonstrate potential and
limitations of this approach.