ANP Research Projects

We want to apply near-field scanning optical microscopy (NSOM) techniques to study light emission of quantum dots interacting with “random cavities” in photonic-crystal slab waveguides. In the waveguides, made by a team from the Danish Technical University (DTU), light scatters randomly from structural disorder stopping its propagation by interference, a phenomenon called Anderson localization. Mapping out the quantum dots and the localized light with the ultimate resolution of an NSOM allows us to extract a wealth of novel data such as the distribution of localization lengths of the modes and their spatial and spectral distribution. Since the light-emitting properties of the quantum dots are best at low temperatures, cryogenic experiments are planned.

Research group: Optical Sciences (OS) & Complex Photonic Systems (COPS)

PhD students: Simon Huisman & Amandev Singh (OS/COPS)

Supervisors: Jennifer Herek (OS), Willem Vos (COPS), Pepijn Pinkse (ANP)

More information: http://os.tnw.utwente.nl/, http://cops.tnw.utwente.nl

The enhanced EM field near metal nanoparticles the support surface plasmons can modify the emission of molecules. For single particles, the benefit of the excitation enhancement by the enhanced EM field is mostly overcome by the very low QY of the emission because of quenching by the metal. However, in between particles (the ‘hot spot’), the field enhancement is much larger than for single particles, and the emission QY is higher.

Simplified representation of the aggregation process. Alpha-synuclein monomers can aggregate and form oligomers, which in turn can form fibrillar structures, which are the main component of Lewy Bodies that are found in the brain of patients having Parkinson’s disease.

Current lithography systems are at their resolution limit (32 nm). In order to further increase the resolution (22 nm, 16 nm and beyond) it is planned to reduce the operational wavelength from 193 nm to 13.5 nm (Extreme Ultra Violet, EUV). In order to increase the optical resolution and optical power throughput and to make the EUV lithography process feasible, a novel dynamic adaptive optics approach is being developed. The Smart Multilayer Interactive Optics for Lithography at Extreme UV Wavelengths (SMILE) project combines active material (piezoelectric, pyroelectric) techniques and the multilayer Bragg reflecting optical systems in order to dynamically correct the degradations in the projected wavefront and to tune the multilayer spacing to increase the total reflected optical power.

Research group: Laser Physics and Non-Linear Optics (LPNO)

PhD student: Muharrem Bayraktar,

Supervisor: dr. Chris Lee, Prof. dr. Fred Bijkerk (LPNO/TNW)

More information: http://lpno.tnw.utwente.nl/index.php?mod=research&projectid=204

There is currently a fast-growing interest in “plasmonic” systems, where light is confined with metallic nanostructures. Due to the strong interaction of the nanostructures and the light field, novel properties arise, called surface plasmon polaritons. This intricate form of light is vigorously pursued with the goal to realize ultimate-small optical integrated circuits, or highly sensitive sensors for medicine and biology.

While surface plasmons have many exciting optical properties, they have a propagation length (or lifetime) that is limited, notably by radiative losses. Therefore, we wish to control plasmonic properties by modifying the environment of the whole plasmonic system. To this end, we will place the plasmonic system inside a photonic crystal. Photonic crystals have a demonstrated ability to control radiative lifetimes of matter such as quantum dots and dye molecules, as pioneered by our group (Nature 430 (2004) 654; Phys. Rev. B 75 (2007) 115302).

Research group: Complex Photonic Systems (COPS)

PhD student: Elahe Yeganegi

Supervisors: Willem L. Vos, Allard P. Mosk

More information: http://cops.tnw.utwente.nl

Applying the unique properties of THz radiation to biological, pharmaceutical, medical, and also industrial processes requires a novel type of source with sufficient power in a compact form. For this goal, in this project, we aim on realizing a photonic free-electron laser. To pump the laser, multiple electron beams are streaming through a photonic crystal where each electron beam generates Cerenkov radiation. The photonic crystal provides phase matching between the electron beams and the radiation field. The transverse scattering inside the crystal also locks the phase between the beams, thus providing a single, transversely coherent radiation wave. This enables to up-scale the laser transversely, by adding more electron beams, which increases the output power and maintains full coherence of the generated radiation.

Research group: Laser Physics and Non-Linear Optics (LPNO)

PhD students: Joan Lee and Thomas Denis

Supervisors: Peter van der Slot and Klaus Boller

More information: http://lpno.tnw.utwente.nl/index.php?mod=research&projectid=25

Contrary to the general belief that scattering of light always leads to a deterioration of image quality, we developed a scattering lens that resolves structures with an unprecedented optical resolution. By carefully manipulating the phase of the illumination beam, we turn the scattered light into a scanning nano-focus in the object plane of our lens. Raster-scanning this focus over our objects yields a high resolution image at sub-100 nm resolution; much better than what is possible with even the most expensive commercial microscope objectives. The scattering lens can be combined with a wide range of existing microcopy techniques to bring even higher resolutions.

Research group: Complex Photonic Systems (COPS)

PhD students: Elbert van Putten (COPS)

Supervisors: Allard Mosk (COPS), Ad Lagendijk (COPS/PS)

More information: http://cops.tnw.utwente.nl/

We want to study superdiffusion using the research tools from the field of wave transport. The main goal is to observe interference effects on wave transport in the unexplored regime of strongly inhomogeneous scatterer density.

In the textbook case of normal diffusion, particle transport is described as a random walk to which all the steps give the same contribution (Brownian motion). Superdiffusion occurs when the transport is dominated by a few very large steps. In this regime the variance of the step length distribution diverges and the mean square displacement grows faster than linear with time. The delicate interplay between wave interference and superdiffusion will be studied in the context of mesoscopic light transport and nanophotonics of disordered media.

Research group: Complex Photonic Systems (COPS)

Postdoc: Jacopo Bertolotti (COPS)

Supervisor: Allard P. Mosk (COPS)

More information: http://cops.tnw.utwente.nl

Semiconductor lasers find a huge variety of applications from telecom to microscopy and display technology. Our goal is to investigate novel approaches in the operation of diode laser by controlling them via integrated photonic circuits. Wavelength tuning and integrated wavelength measurements can be based on high-Q micro ring resonators (MRR) that work as frequency selective mirrors or transmission filters. With employing special read-out and feedback, so-called smart-control, such lasers may also be operated in phased arrays to generate ultra-short pulses with scalable power and repetition rate.

Research group: Laser Physics and Non-Linear Optics (LPNO) & Optical Sciences (OS)

PhD students: R.M. Oldenbeuving

Supervisors: C.J. Lee, H.L. Offerhaus(OS) and K.J. Boller

More information: http://lpno.tnw.utwente.nl/index.php?mod=research&projectid=15

Extreme UV (XUV) and soft-x-ray (SXR) wavelengths are of high relevance for several interesting applications, such as in material science or advanced lithography. However, current optical elements for these wavelengths are limited due to the very short wavelengths (1-10nm), low refractive index contrasts (10-3) and high absorption in these regions. Here, we focus on Lamellar Multilayer Gratings, which offer significant resolution improvements for SXR monochromatization. A coupled-waves approach has been developed for the simulations of LMGs and a novel fabrication process is being investigated in the MESA+ Nanolab facility. These LMGs are a first step towards several different possible types of Bragg-Fresnel optics for the EUV/SXR wavelength region.

Research group: Laser Physics and Non-Linear Optics (LPNO)

PhD students: Robert van der Meer

Supervisors: H.M.J. Bastiaens, F. Bijkerk, K.J. Boller

More information: http://lpno.tnw.utwente.nl/

Coherent anti-Stokes Raman scattering (CARS) is an optical technique that is used to selectively probe molecular vibrations. Every molecule has a unique set of chemical bonds that define its structure, and so has a specific spectral “fingerprint” that can be used to identify it. Two key drawbacks with CARS in general are a persistent non-resonant background that can significantly reduce contrast, and the nonlinear dependence of the detected signal on laser power and molecular concentrations. We develop new methods to resolve these issues and enhance the specificity and sensitivity of CARS, and apply these techniques to elucidate the microscopic details of complicated and interesting samples, such as those from biomedical technologies and pharmaceutics.

Research group: Optical Sciences (OS)

PhD students: Erik Garbacik and Andrew Fussel

Supervisors: Herman Offerhaus and Jennifer Herek

More information: http://os.tnw.utwente.nl/

Coherent anti-Stokes Raman scattering (CARS) is an optical four-wave mixing process that allows for label-free identification of molecules based on their vibrational response. We use broadband excitation to excite multiple vibrational resonances simultaneously. Spectral phase shaping of the excitation pulses allows for the coherent mixing of these resonances, where the pulse shape causes different vibrational states to interfere either constructively or destructively. Our goal is high speed microscopy with chemical selectivity, specificity and sensitivity by tailoring the spectral phase of the excitation light.

Research group: Optical Sciences (OS)

PhD student: Alexander C.W. van Rhijn

Supervisors: Herman L. Offerhaus, Jennifer L. Herek

More information: http://os.tnw.utwente.nl/

Semiconductor photonic structures, especially microcavities, are widely used in science and technology. To switch them on ultrafast time scales, i.e., changing their optical properties while light travels through them, promises new insights in cavity quantum electrodynamics (QED) and is essential in applications such as integrated photonic circuits.

The goal of our study is to switch semiconductor microcavities independent of material constraints. We want then to manipulate the spontaneous emission of emitters inside the cavities on ultrafast time scales.

Research group: Complex Photonic Systems (COPS)

PhD students: Emre Yüce, Nasser Hosseini

Postdoc: Georgios Ctistis

Supervisor: Willem L. Vos

More information: http://cops.tnw.utwente.nl