Research program

Advances in controlling the flow of light are ubiquitous in our daily life. In fact, design-tailored guiding and steering of light by optical fibers and waveguides has paved the way for powerful data networks spanning the globe. Additionally, optical waveguide devices are essential for a optical sensing schemes in metrology, medicine, sensing, and manufacturing technology. Moreover, guided-light-structures provide exceptional opportunities for investigating fundamental concepts of modern physics and for analyzing fundamental aspects of wave dynamics. In recent years, non-classical quantum states of guided light with a high degree of entanglement in space and time have emerged as a thrilling field of research powered by expectations of quantum computing, quantum communication or quantum cryptography. Waveguiding and resonant localization of light in tiny volumes – and their control in space, time, spectrum and quantum state – remain a pertinent scientific and technological challenge. The ultimate demands for integrated optics are to tightly pack optical functions in order to enable smaller devices with better energy efficiency and improved sustainability and to unlock new applications.


Since its start in 2015, the ambitions and challenges of the IRTG 2101 Guided light, tightly packed: novel concepts, components and applications have proven as an exciting field of research, and most fruitful and largely unexplored grounds for teaching and training young-career scientists at a top-notch international level. With the teaming of one German and three Canadian partners, bringing in their complementary competences into the IRTG and already during its first funding phase, more than 50 participating doctoral and postdoctoral researchers are given the opportunity to obtain academic qualification and degrees upon experimental physics in a one-of-a-kind, bi-national and stimulating environment.



Since 2015, the IRTG has established a professional qualification and supervision program, adherering to the highest academic standards. This includes our perception and dedication of how to train and shape self-responsible, mature and innovative young scientists and how to support their careers in any possible way. The IRTG's doctoral researchers are deeply involved in a top-notch research environment, both in Germany and in Canada, and with mandatory research visits abroad. Extensive hands-on experience in laboratories with exclusively research-grade components and equipment is one of the most valuable professional attributes by which a true expert in photonics is distinguished. The doctoral researchers within the IRTG are allowed a maximum freedom to develop their own ideas and to follow personal scientific interests. Our trust in our doctoral researchers’ liberties and their abilities to develop is one of the IRTG's most distinguishing features.


Therefore, and already during its first funding period, the IRTG has opened a unique opportunity to educate young scientists working towards doctoral degrees in Germany and Canada concerning multifold aspects of guided waves and concentrated light, ranging from fundamental concepts over material science to the transfer of fundamental principles into applications. In a top-notch, stimulating, binational surrounding, the doctoral researchers execute both scientific research as well as a well-balanced qualification program at highest standards, which encompasses scientific, transferrable and intercultural aspects, and several researcher stays at the foreign participating institutions to profit from complementary expertise, equipment, and exchange with fellow professors and scientists. The binational interplay between research, academics and professional education will continue to nurture scientists who will be capable of executing internationally recognized world-class research in the future. The counterpart of the research and training programm of this DFG-IRTG on the Canadian side is funded by a CREATE program of the National Science and Engineering Research Council (NSERC).

During the IRT's first funding period, research pillar 1 deals with the fundamental material aspects, design and realization of innovative waveguide structures with unmatched properties and functionalities. Fundamental linear and nonlinear light propagation effects in waveguide structures as realized in pillar 1 as well as the interaction of the propagating light with its environment will be mastered in pillar 2. Finally, pillar 3 will harvest the novel functionalities to realize applications with hitherto unknown precision. Each of these different aspects will be investigated in close collaboration between all the partner institutions in Canada and Germany.

Research pillar 1 - Longitudinal and transversal structured waveguides

1.1 Realization of innovative fiber structures

  • Liquid-core PCF - a new base for soliton propagation in extremely confined geometries
  • Hollow-core chalcogenide glass band gap PCFs for mid-IR applications
  • Super-continuum generation in heavy oxide fibers with artificially enhanced nonlinearity

1.2 Functionalization of optical fibers by defined (laser) structuring

  • Fiber Bragg gratings for microstructure optical fiber - towards high power mid-IR lasers
  • Mode-converters and polarization controlled optical fiber circuits - quantum encryption on fiber
  • Waveguide probed optical resonator cavities - novel spectral filter concepts embedded in fiber


1.3 Optical guiding structures in bulk materials and thin films by laser modification

  • Spatio-temporal control of ultrashort laser pulses for defined modifications inside transparent bulk materials
  • Local control of polarization states by 3D confined artificial birefringence
  • Tailoring the propagation properties in thin-film waveguides by local laser nanostructuring

1.4 Novel functional materials with tailored properties

  • Integrated, waveguide-based magneto-optical isolation using novel materials
  • Sub-wavelength scale electro-optic modulators and switches using hybrid VO2-onsilicon waveguides
  • Realization and investigation of waveguiding structures built from or embedded in periodic structures
  • Investigation of the nonlinear response of PT-symmetric effective materials

Research pillar 2 - Temporal and spatial effects in waveguides

2.1 Linear confinement of guided light waves

  • Localized edge states due to disorder
  • Light evolution in disordered photonic crystals
  • Light tailoring due to artificial defects

2.2 Light confinement inside cavities

  • Limits of topological cavity mode isolation in the strong confinement regime
  • All-optical switching and signal processing at ultra-low powers in optical cavities
  • Pattern formation and spatio-temporal confinement in coupled cavity systems


2.3 Nonlinear propagation effects of guided high intensity light

  • High field THz pulses from filaments driven by long wavelength pulses
  • Exploiting ionization induced nonlinearities in hollow core fibers for supercontinuum generation
  • High average power energetic few-cycle pulses at 2 μm wavelength
  • Compression of energetic laser pulses in large area hollow core fibers
  • Efficient Raman-shifters based on Bessel-beams
  • Spatio-temporal coupling with beams carrying angular momentum

2.4 All-optical routing and switching in waveguide networks

  • Optimization of two-dimensional geometries for the efficient routing of light
  • Blocking and switching of light in waveguide arrays using discrete spatial solitons
  • Data processing on the flight employing the interaction between pulses during their propagation
  • Bit sequence and header recognition in waveguide arrays

Research pillar 3 - Novel optical functions in waveguide components and systems

3.1 Novel fiber laser sources

  • Design and excitation schemes of multi-core amplifying fibers and their coherent combination
  • Investigation of passive and active stabilization of interferometric multi-core fiber amplifier
  • Raman gain fiber lasers for the mid-IR based on fluoride and chalcogenide fibers
  • Supercontinuum generation in the IR/MIR spectral range using ultrashort (femtosecond) pulses

3.2 Integrated quantum systems

  • Integrated quantum sources based on fiber and laser-modified waveguides
  • Quantum walks of correlated photons in a 3D laser-written waveguide lattice
  • Chip-based quantum gates for photon qubits


3.3 Smart fiber-based biosensors

  • Functionalization scheme to develop 3D optofluidic fiber devices
  • Fiber based cell-counting system and plasmonic sensor
  • Multifunctional core-shell nanowires for biosensing applications in a large spectral range
  • Spectral diagnostics and theranostic approaches at plasmonic structures in the near-infrared
  • Silicon nanostructure-decorated optical fibers: formation and optical loss optimization