Research Labworks for MSc

Seeing is believing. This sentence is as true as it is tricky. Most cellular components and processes, crucial for the nuanced understanding of (human) life, are not observable by conventional light microscopy since Abbe’s Law describes their maximum resolution to roughly half the wavelength of the observed light. This law is literally set in stone in Jena. However, over the past 15 years several ways of cleverly circumventing this diffraction limit were developed and implemented, achieving three-dimensional resolutions down to the nanometer range, resulting in the ever-growing field of optical super-resolution microscopy, for which the 2014 Nobel Prize in Chemistry was awarded.

The aim of this projects is to introduce, understand and apply the principles of state of the art fluorescence microscopy techniques, used e.g. in a broad range of modern biomedical and cell-biological research. Students prepare their own, fluorescently labeled, biological samples and will image them on a variety of advanced microscopes with different (resolution) capabilities. The qualitative and quantitative comparison of acquired images will illustrate the advantages and limitations of the respective microscopy technique.

Goals and Context

• Principles and application of advanced fluorescence microscopy techniques
• Concept of diffraction-limited and super-resolution
• Preparation of fluorescently labeled, biological samples
• 3D & multi-colour imaging at the nanoscale

Methods

• Cell culture and wet lab
• Fluorescent labeling
• A selection of advanced fluorescence microscopy techniques from the IAOB toolbox:
  • Confocal Laser Scanning Microscopy
  • Array Scan Microscopy
  • Stimulated Emission Depletion (STED)
  • Structured Illumination Microscopy (SIM)
  • Single-Molecule Localization Microscopy (SMLM)
  • MINFLUX Nanoscopy
• Image analysis by Fiji/ImageJ

Prerequisites

• An open mind and motivation for independent thinking
• Students should be able to explain the general difference between confocal and widefield microscopy and have basic knowledge on the concepts of super-resolution microscopy (e.g. Abbe’s diffraction limit)
• You should know the basic principles of fluorescence

A good preparation for the course is the biophysics lecture from Prof. C. Eggeling

Person in charge: Christian Franke & Katharina Reglinski

Supervisors: Christian Franke & Katharina Reglinski         

Venue: Microscopy Labs of the IOAB in the ZAF and Abbeanum or at the IPHT (Beutenberg)

The topic is suitable for two groups with 1-2 students each.

Advanced measurement techniques and stable optical systems are crucial for scientific research 
breakthroughs in fields like quantum optics, spectroscopy, and fundamental physics. These 
techniques enable precise probing of matter and light properties, as well as detection of phenomena like gravitational waves. At the core are stabilization methods for optical cavities and lasers. Optical cavities enhance light-matter interactions for high-precision measurements. Cavity stabilization ensures reliability and precise control over photon generation and manipulation. The presentation will cover general principles and techniques for stabilizing optical systems, beyond specific applications. It will explore advanced stabilization methods like Side-of-Fringe (SOF) locking and Pound-Drever-Hall (PDH) locking, which have wide applicability in diverse scientific settings.

Teaching Goals and Content

• Understand the principles and importance of optical cavities in current technologies.
• Design and construction of an optical cavity.
• Calculations of the mode-matching optics of a cavity by using ABCD matrix.
• Explore the Side-of-Fringe (SOF) locking technique for cavity stabilization.
• Explore the Pound-Drever-Hall (PDH) locking technique for stabilizing optical cavities by using radiofrequency techniques.
• Compare and contrast the SOF and PDH locking techniques in terms of performance and applicability.
• Analyze the stability and reliability of the optical cavity using these locking techniques.

Experimental Techniques and Equipment

• Optical alignment of optical cavities.
• Continuous wave pump lasers at suitable wavelengths.
• Photodetectors for monitoring the cavity's reflected and transmitted light.
• Electro-optic modulators for phase modulation in the PDH technique.
• Lock-in amplifiers for demodulation and proportional-integral (PID systems) for feedback control.
• Data acquisition systems for recording and analyzing the locking signals.

Contact:

Place: Fraunhofer IOF institute

Supervision: MSc. L. Gonzalez

For this experiment two students are recommended.

Nowadays the generation of ultra-short laser pulses with a duration down to some femto seconds is state of the art. Such pulses find their application not only in the field of scientific research to investigate ultra-fast processes, to perform ultra-precise spectroscopy, or to generate extreme electrical and magnetic fields through ultra-high light intensities, but they are also applied in material processing, medicine, especially in ophthalmology. Nevertheless, the generation and metrology of ultra-short pulses require complex measurement techniques. The basics to understand the underlying effects of pulse generation, stretching and compression as well as their measurement will be taught here. Some of these effects are based on non-linear optics and frequency conversion, that requires phase matching to get reasonable efficiencies. Second harmonic generation and two-photon absorption are used for pulse characterization by auto-correlation here. The limitations of the auto-correlation for the reconstruction of the temporal behavior of the laser field will be investigated in more detail.   

Teaching goals and content 

• Working principle and properties of solid-state lasers (Ti:sapphire)
• Cavity stability and longitudinal cavity modes
• Dependence of output power on pump power
• Generation of femtosecond pulses by Kerr-lens mode-locking
• Compensation of group velocity dispersion in optical cavities
• Impact of spectral phase on pulse duration and temporal pulse shape
• Measurement of band-width and duration of laser pulses
• Application of Fourier-Transform to explain pulse stretching and compression
• Interferometric and intensity auto-correlation and their limitations for pulse characterization
• Measurement of group velocity dispersion (GVD) of several materials

Experimental techniques and equipment

• diode-pumped, frequency-doubled 5W Nd:YV0₄-laser as pump source
• homemade Ti:sapphire femtosecond laser with prism GVD compensation
• external prism pulse compressor
• optical spectrometer
• second harmonic generating auto-correlator
• photodiodes, powermeter and oscilloscope

Contact:

Supervisor:   Dr. Joachim Hein

Place:  F-Praktikum

For this experiment two students are recommended.

In modern optical imaging, precise methods for investigating micro- and nanoscale structures are of great importance. Diffraction imaging revolutionizes optical imaging by foregoing traditional optics and instead relying on computer algorithms to create high-resolution images. Despite its potential, there are significant challenges in reconstructing images from diffraction patterns.

The main focus of this project is to investigate the optical diffraction imaging in the visible range. The various influences such as the size of the illumination spot, the coherence, the structure size, the monochromaticity or bandwidth and the overlap with other beams in the visible spectral range will be taken into account. A particular focus will be on exploring the convergence of reconstruction algorithms as a function of the above parameters. In particular, multicolor diffraction still raises many fundamental questions.

Teaching Goals and Content 

• Design and construction of an optical test setup
• Basics of diffraction imaging and ptychography
• Influence of various light sources on imaging
• Development and application of reconstruction algorithms
• Experimental applications and diagnostic methods

Prerequisites

• Basics in optics, Fourier optics, and image processing
• Interest in modern imaging and algorithm development
• Experimental skill and problem-solving ability
• Basic knowledge in programming, ideally in Python or Matlab

Contact:

Supervisor: Dr. Martin Wünsche and Dr. Jan Rothhardt

Place:  Max-Wien-Platz 1 and Albert-Einstein-Str. 6

The topic is suitable for two groups with 2 students each.

Spatial laser beam characterization plays a critical role in ultrashort pulsed laser material processing, where precision and control are essential for achieving desired outcomes. The primary importance of spatial beam characterization lies in its ability to provide accurate data about the energy distribution, fluence, and intensity profile of the laser beam. These parameters are crucial in determining how the laser interacts with the material, influencing the quality, efficiency, and reproducibility of the process. In material processing, such as micromachining or surface structuring, understanding the spatial energy distribution helps identify inconsistencies that can lead to defects or poor quality results. Similarly, in nonlinear optics, where processes like harmonic generation and multi-photon absorption are highly intensity-dependent, spatial beam characterization reveals how localized intensity affects the efficiency of these effects.

The goal of this project is to build and characterize an automated setup to record and analyze the spatial properties of beams from ultrashort pulsed laser systems. In addition, different laser sources and beam shaping systems should be characterized.

Teaching goals and content

•  Fundamentals and methods for laser beam characterization
•  Basics of spatial beam shaping
•  Alignment and characterization of optical setups
•  Development and automation of measurement procedures
•  Image processing and data analysis

Prerequisites

•  Basic knowledge in optics
•  Good experimental skills
•  Programming with Python, Matlab or LabView

Contact:

Supervisor: Hagen Kohl

Place:  Institute of Applied Physics (IAP, Beutenberg)

The topic is suitable for one or two students.  

Interaction of intense ultrashort laser pulses with crystalline solids might excite a coherent vibrational motion in the lattice having ultrafast time scale – from several tenses to several hundreds of femtoseconds. The physical mechanism of the excitation is typically the Raman excitation, when nuclear motion is triggered by the electron polarization driven by intense laser pulses, whereas the type of the excited vibrational modes depends on relative orientation of the laser polarization in respect to the symmetry axes of the crystal.

The goal of the suggested project is the experimental investigation of time-dependent dynamics of lattice vibrations in a very novel magnetic semiconductor layered material CrSBr excited by intense, ultrashort laser pulses. The experiments are based on a pump-probe technique when an intense, ultrashort laser pulse excites vibrational motion of the lattice via the resonant stimulated Raman scattering, and the corresponding phonon dynamics is probed by a weak pilot ultrashort pulse. Specifically, a novel detection scheme will be used, that is based on the dynamically changing birefringence, induced in the material due to the lattice motion. This detection scheme involves a box-car integrator and lock-in amplifier detection to achieve a very high sensitivity. The spectrum and the temporal evolution of the coherent phonons will be measured as a function of crystal orientation and the intensity of the pump laser pulses.

Prerequisites

• Basics knowledge in optics
• Good experimental skills
• LabView as highly desirable skill

Contact:

Supervisor:         Dr. Daniil Kartashov

Place:                  Institute of Optics and Quantum Electronics (IOQ, Max-Wien-Platz 1)

The topic is suitable for one or two students.

Ultrashort pulse lasers are nowadays one of the most interesting types of lasers, since they have opened up new applications in the scientific, medical and industrial fields. In fact, achieving ultrashort pulses (<1ps) is a unique ability of lasers that separate them from other light sources. Usually such ultrashort pulses, which are some of the shortest events ever created by Mankind, are obtained using the technique of mode locking, which has become one of the most important methods in modern lasers.

Additionally, among all available laser architectures, fiber lasers have stablished themselves as one of the most attractive types of lasers due to their simplicity, efficiency, low-cost, maintenance-free nature, compactness, robustness and high-power scalability. In fact, fiber lasers are currently replacing more traditional types of lasers in many applications.

In this project, you will get to know fiber lasers by building and characterizing a mode-locked fiber laser able to deliver several 100 fs pulses. In this project you will build the cavity, try out different configurations and learn about the physics of mode locking. At the end, you will have created from scratch one of the most appealing types of lasers: an ultrafast fiber laser.

Teaching Goals and Content

• Understand the principles of mode-locking and fiber lasers.
• Design and construct a fiber cavity.
• Use of Semiconductor-Saturable Absorber Mirrors (SESAMs) to achieve mode-locking.
• Learn to characterize an ultrafast laser.
• Analyze the performance of the laser as different parameters of the cavity are changed.
• Perform simulations of the laser.

Experimental Techniques and Equipment

• Handling of optical fibers (stripping, cleaving, splicing, etc).
• Coupling of optical radiation in/out of a fiber.
• Use of SESAMs.
• Systematic characterization of the laser performance using, e.g. power meters, spectrometers, etc.

Contact:

Supervisor:     Cesar Jauregui & Jan Rothhardt

Place:              Institute of Applied Physics/Abbe center of Photonics

This experiment can be carried out by one of two students.

According to de Broglie matter has not only particle but also wave character. It was shown that electrons, due to their rest mass, already exhibit wavelengths of around 1 angstrom at acceleration voltages of about 150 V, which is in the range of atomic distances in solids. Crystals therefore represent natural diffraction gratings for accelerated electrons, just as they do for X-rays of similar wavelengths. However, due to the strong inelastic interaction between electrons and atoms, the inelastic mean free path of electrons in solids ranges from less than 1 to several 100 nm which is thus considerably smaller than for X-rays. This makes electron diffraction especially suited for the investigation of crystalline surfaces and thin layers.

The aim of this projects is to understand principles of electron diffraction, especially reflection high energy electron diffraction (RHEED) and low-energy electron diffraction (LEED), which are a widely used characterization method for inorganic compounds with the ability of in situ growth monitoring of thin films. Students prepare their own samples, starting from cleaning single-crystal surfaces, followed by the deposition of films via molecular beam epitaxy as well as their structural characterization by means of RHEED and LEED. All preparation and analyzing steps are performed under ultrahigh vacuum (UHV) conditions.

Goals and context

• principles and application of electron diffraction in two dimensions (2D)
• concept of reciprocal space
• preparation of atomically clean single crystals and two dimensional materials
• highly-ordered ultrathin layers by molecular beam epitaxy
• vacuum technology (pumps, gauges, rest gas analysis etc.)

Methods

• UHV chambers with:
  
  • RHEED device (electron gun, phosphor screen, camera)
  • MCP-LEED (electron gun, phosphor screen, micro channel plates, camera)
  • sputter gun and sample heater
  • vacuum pumps (roughing, turbo, ion getter, and titanium pump)
• metal single crystals as sample substrates
• effusion cells for deposition

Contact:

Supervisor: Dr. Felix Otto    

Venue: Labs of AG Fritz (ZAF)

The topic is suitable for two students.

Hardly any other topic inspires the intellectual curiosity in the past decades such as nanotechnology. In addition to the enormous range of applications in the semiconductor, textile and automobile industry, mechanical engineering, architecture, aerospace engineering, medical and energy technology, it also provides an interesting insight into the physical and chemical processes and properties at the atomic and subatomic level. In this field the so-called carbon nanotubes are of particular importance. Since their discovery in 1991 by Sumio Ijima and his research group as well as the experimental studies of Bethune et al., different research groups largely succeeded to understand the production mechanism of these nanoscopic structures and their wide potential for applications. Beside to their high tensile strength and elasticity they have extraordinarily good conduction properties. In research they are therefore used as electronic components such as field effect transistors and electrical sensors and as probes for scanning force and scanning tunneling microscopes. In the industry they are used, among others, as conducting composites.

In this project, CNTs are grown by means of the chemical vapor deposition (CVD) technique. First, the substrates needed shall be prepared by the student itself and, especially, the for the CVD process required catalyst (cobalt or iron) shall be grown structured by means of the thermal deposition method. The characterization of the substrates and CNTs shall be done by means of atomic force microscopy (AFM) and Auger electron spectroscopy (AES) as well as scanning electron microscopy (SEM) and Raman spectroscopy, respectively. The letter is a widely-used optical analysis tool, which is perfectly suited to gain information about the quality of the CNTs as well as their structures to a certain extent. After optimizing the process parameters of the CVD, self-made CNT networks shall be tested in terms of their performance as gas sensors (FET setup). For this purpose, I-V curves are measured computer-aided in dependence of different environmental parameters (partial pressure of the gas to be detected, temperature, …).

Objectives

• Nanotechnology / Nanostructures
• Carbon nanotubes - structure, properties, preparation, growth, use, characterization
• Coating processes (in particular chemical and physical gas-phase deposition)
• Sample preparation
• Vacuum technology
• Learn about chemical vapor deposition (CVD) systems
• Using the scanning electron microscope (STM) or atomic force microscope (AFM)
• Application of Raman spectroscopy
• Electrical characterization: I-U, sensor properties

Experimental techniques

• CVD equipment, medium vacuum
• Samples: single crystalline silicon with oxidic passivation and quartz with catalyst coating of both substrates
• Vacuum coating, thermal evaporation
• Raman spectrometer
• Scanning electron microscope (SEM)
• Atomic Force Microscope (AFM)
• Auger electron spectrometer (AES)
• Computer-aided measurements of I-V curves

Contact:

Supervisor:      Dr. Marco Grünewald

Venue:            F-Praktikum and labs of the IFK

The topic is suitable for one or two students.  

Ion sources are applied in a wide range of processes for e.g. doping, quantum dot fabrication and the creation of buried layers. For theses purposes, broad beam ion sources can be utilized to maintain fast processing times even on large implantation areas.

In 2022, operation of a unique four-grid accelerator broad ion source (4GABIS) started at the IAP Jena. Within 4GABIS, ions are accelerated from a plasma source with voltages of up to 30 kV in a beam of around 180 mm diameter. Currently, 4GABIS is not completely characterized for all of the available acceleration parameters. Hence, the first goal of the experiments is to investigate the effect of grid voltages on the resulting shape of the beam profile. This will be measured both directly with a movable faraday cup and indirectly via resulting sputter rates. The insights of this will subsequently be applied to establish ratios between the flux of ions hitting the target and the faraday cup in measurement position, respectively. Next to that, the impact of neutralisation of ions during their flight via charge transfer will be measured. From this, charge transfer cross sections can be calculated and compared with the literature. The combined results are to be integrated into a pre-existing LabVIEW program to allow for in-situ measurement of ion flux.

Summary of the main goals for this experiment:

1. Understanding the shaping of a hot-cathode glow discharge plasma
2. Investigation of grid voltage parameters to affect the resulting ion beam
3. Measurement of charge transfer cross section for collisions of ions and residual gas
4. Combining parameters necessary for in-situ monitoring of ion flux

Prerequisites:

• Basic understanding of hot cathode glow discharge and ion acceleration
• Basic knowledge of LabVIEW programming
• Good laboratory skills
• Interest in operating a unique ion source

Contact:

Supervisor: Johannes Kaufmann

Venue: Institute of Applied Physics, Beutenberg Campus (Albert-Einstein-Str. 15)

The topic is suitable for one or two students.

Two dimensional materials show some unique optical properties, many of which arising from the quantum confinement that leads to a strong binding of excited electrons and the positively charged hole. Some experiments, e.g. for the study of nonlinear optics and many body physics, require high laser excitation powers which leads to a problem that has so far not been studied in detail: local heating by the laser radiation. This is especially crucial in experiments where the excitation power is scanned from low and high, since the different temperatures will lead to secondary effects that make any interpretation difficult. To mitigate the heating effects or include the heating into the models appropriately, we first need to learn more about the magnitude of said temperature increase. In our labs we work with many different materials, wavelength-ranges and temperatures from ambient down to 14 K and it can be expected that each configuration will be unique, but for our first investigation that will be detailed below, we will pick the class of 2D materials known as transition metal dichalchogenides (TMDs), because they possess a Raman peak that is known to be temperature sensitive.

In the experiment we will place the sample on a thermostat and perform a measurement of this Raman peak with very low excitation power which is expected to leave the temperature nearly unchanged. By tuning the temperature of the thermostat, a correlation of peak position and temperature can be established. After that, we repeat the experiments, only this time the thermostat remains fixed at the lowest temperature and the excitation power is increased. Again, the peak position is monitored, which yields the correlation between laser powerand peak position. By combining the two results we can determine the influence of laser power on temperature.

Objectives:

• Temperature dependence of Raman mode in TMDs
• Laser induced heating in TMD

Experimental techniques:

• Raman scattering
• Cryostat/thermostat
• Two-dimensional materials

Contact:

Supervisor: M.Sc. Muhammad Hussain

Venue: GUFOS, IFK (Room E011)

The topic can be worked on by one or two students. Supervision is possible in English only.

Single crystalline metal layers on natural mica are often used in electronic devices such as transistors, solar cells, and sensors, due to their high electrical conductivity and mechanical stability. Additionally, they can be used as a substrate for growing other single crystalline materials, such as semiconductors, which can be used in electronic devices as well. The high thermal and chemical stability of natural mica also makes it an ideal substrate for a wide range of applications, such as in the aerospace and automotive industries. Overall, the cost-effective fabrication of single crystalline metal layers on natural mica can have a significant impact on the development of new technologies and the improvement of existing ones.

The experiment aims to fabricate and investigate the properties of single crystalline metal layers using a thermal evaporation method. In this process, the metal material will be thermally evaporated onto a substrate of natural mica under specific conditions, such as temperature, pressure, and evaporation rate, to achieve single crystalline growth. The substrate will be carefully chosen, cleaned and prepared to ensure optimal growth conditions.

The characterization of the fabricated metal layers will be done using a combination of techniques including atomic force microscopy (AFM) and x-ray diffraction studies (XRD). The AFM will be used to observe the surface morphology of the metal layers, including the thickness, uniformity, and surface roughness. The XRD will be used to determine the crystal structure of the metal layers, including the crystal size, lattice spacing, and crystal orientation, as well as to identify any defects or impurities in the crystal structure.

The goal of the experiment is to understand how the thermal evaporation fabrication method and process conditions affect the properties of single crystalline metal layers and how such layers can be used in various applications such as electronics, catalysis, and sensing. The experiment will also help in understanding the relationship between the growth conditions and the crystal structure and will provide a better understanding of the fundamental physics of metal growth.

The main goals of this experiment are:

• Fabrication of single crystalline metal layers using thermal evaporation
• Investigation of the structural and morphological properties

Prerequisites:

• Familiarity with basic laboratory techniques
• Basic understanding of crystal growth and crystal structure

Methods:

• Thermal evaporation setup
• Atomic force microscopy (AFM)
• X-ray diffraction studies (XRD)

Contact:

Supervisor: Dr. Marco Grünewald and Dr. Berit Marx

Language: German or English

Venue: F-Praktikum and labs of the IOQ

The topic is suitable for one or two students.

Micro- and nanotechnology forms the basis for a growing number of everyday objects and current scientific research. Many physical systems require a direct examination or at least a basic understanding of this technology chain.

The theoretical foundations are already taught at the FSU as part of the Micro/Nanotechnology lecture in the Physics or Photonics Master's programme and the associated seminar. Practical training has not yet been provided. This gap is to be closed by expanding the programme of the lab course.

The aim of this offer is to gain initial experience with an existing lithography line in the clean room and to jointly develop a concept for how this can be used for future teaching.

Contact:

Supervisor:   Dr. Thomas Siefke

Venue:           Clean room of the IFK and F-Praktikum

The topic is suitable for one or two students.

Many modern quantum light sources for quantum technologies such as quantum cryptography, quantum key distribution and ghost imaging are based on the process of spontaneous parametric down-conversion (SPDC). This process splits one pump photon into an idler and a signal photon and requires a material with a second order nonlinearity; it can be envisioned as the „inverse“ process of second harmonic generation (SHG). Current state of the art quantum light sources use periodically poled bulk crystals, in order to achieve necessary conversion efficencies. However, these bulky crystal make an implementation onto existing photonic structures, like fibres and waveguides, impossible.

Recently, the novel material class of layered ferroelectrics has emerged. Ferroelectrics show strong second order nonlinearity, independent of the layer number, and can be exfoliated to atomically thin layers. This culminated in researchers being able to build an ultrathin quantum light source from NbOCl₂, one member of the family of layered ferroelectrics.

In this series of experiments, we will investigate the nonlinear optical properties, namely second and third order nonlinearities, of the layered ferroelectric NbOI₂. We will theoretically and experimentally study the second and third order nonlinear response of NbOI₂, by performing  second harmonic generation (SHG, the simplest second order nonlinear process) and third harmonic generation (THG, the simplest third order nonlinear process) measurements, focusing in particular on their power and polarization dependence. Finally, we will discuss the concept of angular momentum of light and we will experimentally study SHG and THG in NbOI₂  when the fundamental beam is tuned from linear to circular polarization.

Working plan:

Weeks 1-4: introduction to SHG in NbOI₂, dependence of SHG on thickness, input power and crystal axes, polarization resolved SHG (resolving crystal axes, out-of-plane SHG)

Weeks 5-8: introduction to THG in NbOI₂, dependence of THG on thickness, input power and crystal axes, comparison to SHG

Weeks 9-12: angular momentum of light, SHG & THG for linear to circular polarization

Objectives:

•  Layered ferroelectrics: band structure, optical properties and crystal symmetry
•  Nonlinear optics: basic theory, nonlinear susceptibility tensors for SHG and THG
•  Polarization optics (Quarter wave plate, half wave plate…..)

Experimental techniques:

•  Second harmonic generation (SHG)
•  Third harmonic generation (THG)
•  Low noise and lock-in detection

Contact:

Supervisor: Paul Herrmann

Venue: GUFOS, IFK (Room E002)

The topic can be worked on by one or two students. Supervision is possible in English and German

Thin layers are layers with thicknesses in the micrometer and nanometer range. Their physical parameters such as electrical conductivity often deviates from that of the bulk material, allowing for altered, tailored properties and new functionalities. In addition, the material savings are often of great economic importance. Well known is the application in the field of protection against environmental conditions, e.g. against corrosion or oxidation. However, thin layers are most important in microelectronics, where almost all components are manufactured using thin-film technology. In optics, thin layers and layer stacks are used to influence the reflection and transmission behavior, but also the polarization. In particular, layer systems play a prominent role in X-ray optics.

In the internship, metallic layers are usually deposited and characterized by different methods. Concrete topics and goals, amongst others taken from current research projects, are proposed by the supervisor at the beginning of the internship, but can be discussed and adapted depending on the interests.

Learning goals and content:

• Deposition of thin metal layers by means of various coating methods (sputter coating, thermal evaporation)
• Characterization of the layer properties (e.g., composition, roughness, crystalline properties) depending on substrate properties and coating parameters (e.g. chamber pressure, residual gas composition, process times, substrate heating)
• Introduction and application of various analysis methods
  • Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX)
  • Scanning Tunneling or Atomic Force Microscopy (STM, AFM)
  • Auger Electron Spectroscopy (AES)
  • X-ray diffractometry (in cooperation with the X-ray group)

Experimental equipment:

• Sputter coating system from Oxford Instruments
• Thermal evaporation system (self-made)
• Mass Spectrometer for residual gas analysis
• Quartz layerthickness monitor
• Scanning Electron Microscope
• Atomic Force Microscope
• Scanning Tunneling Microscope
• Auger Electron Spectrometer

Contact:

Supervisor:   Dr. Thomas Siefke

Venue:           F-Praktikum

The topic is suitable for one or two students.

The recent emergence of nanomedicine has revolutionized the therapeutic landscape and necessitated the creation of sophisticated drug delivery systems. Polymeric nanoparticles sit at the forefront of numerous promising drug delivery designs, due to their unmatched control over physiochemical properties such as size, shape, architecture, charge, and surface functionality. Hence, a precise understanding of polymeric nanoparticles preparation and characterization is essential for optimizing the drug delivery system.

We will prepare polymeric nanoparticles with various sizes and crystallinities and characterize them by size investigation and morphology. The application of the materials is not just interesting for basic research but also promising for the targeted delivery of drugs with optimized structures.

The aim of this work is to develop a comprehensive understanding of polymeric nanoparticles as drug delivery vehicles, using the various nanoparticle designs and preparation methods. If you are interested in new, future-oriented frontier materials and physico-chemical aspects and like to work experimentally, then join our international team.

Goals and context

•  Creation of nanostructured polymeric materials
•  Characterization and analysis of these materials
•  Structure elucidation of the materials
•  Structure-property relationships of materials
•  Insight into current research and development fields in nanotechnology and smart-functional materials methods

Methods

•  Advanced literature research
•  Elaboration of nanoprecipitation methods
•  Analysis of polymeric nanoparticles, using atomic force microscopy (AFM), electron microscopy (SEM, TEM), UV-Vis, dynamic light scattering (DLS), etc.
•  Determination of the mechanical properties of polymeric nanoparticles

Prerequisites

•  Interest in materials science, nanophysics and soft matter physics

Contact:

Person in charge: Prof. Dr. Klaus D. Jandt

Supervisor: Dr. Chuan Yin

Venue: OSIM, Löbdergraben 32

The topic is suitable for two students. Up to tow student pairs (2 x2) may work on this topic.

Context: 

Modern day optical techniques have enabled physicists to structure the intensity, phase and polarization of the light beams. For example, Laguerre-Gaussian and Bessel light beams have structured intensity profile. Thus, these light beam’s intensity profile appears as donut with a dark center. These light beams are often referred as twisted light beams. In addition, these light beams can be used to construct vector light fields. These vector light fields demonstrate richer polarization pattern. Interaction of these light fields with atomic targets has found numerous applications in the field of optical metrology, quantum computers, atomic clocks and many more.

In this project, we wish to analyze photoexcitation of atomic cloud using various vector light modes and analyzing the properties of fluorescence radiation. Thus, in the end to have a detailed comparison between various light fields and atomic targets.

Goals of the project:

•  To express the interaction phenomena in terms of density matrix theory
•  To express vector light beams in Laguerre-Gaussian and Bessel basis.
•  Description of the light-atom interaction using time dependent perturbation theory
•  To better understand paraxial and non-paraxial nature of light fields.

Prerequisites:

•  Knowledge of Quantum Mechanics
•  Programming skills: Julia or Mathematica.

Contact:

Person in charge: Prof. Dr. Stephan Fritzsche, Theoretisch-Physikalisches Institut

Supervision: Shreyas Ramakrishna

Place: Theoretisch-Physikalisches Institut & Helmholtz-Institut Jena, Frauenhoferstr. 8.

Per term, one or two students may work on the project

The dielectronic recombination (DR) of multiply and highly-charged ions involves the capture of an electron due to the resonant excitation of another bound electron as well as their subsequent stabilization by photon emission. The DR process has been found essential for understanding the dynamics of highly-ionized plasma in astrophysical objects, fusion reactors, and at several places elsewhere. In astrophysics, for example, DR affects the ionization balance of gas in galaxy clusters and the intergalactic medium and, hence, the formation of stars and  large-scale structures in the universe.

In this project, we wish to explore and compute the DR resonance strength for the capture of electrons by (selected) hydrogenic ions with medium or high nuclear charge, Z. This requires to determine and apply solutions to the Dirac equation as they are provided by several (atomic) codes. We wish to analyze the low-lying DR spectrum for such ions and to compare our theoretical predictions with available experimental data.

Goals of the project

•  Recall the treatment of one- and few-electron ions in terms of wave functions.
•  Formulate the DR resonances strength by means of two-electron matrix elements.
•  Describe the interaction of atoms with a weak radiation field.
•  Understand and apply an existing (Julia) code in order to compute the DR strength and plasma rate coefficients.
•  Optional: Compare different theoretical models and how well they compare with experiment.

Prerequisites:

•  basic knowledge of quantum mechanics
•  programming skills (Python, Julia, C)

Contact:

Supervision:  Prof. Stephan Fritzsche, Theoretisch-Physikalisches Institut

Where: Theoretisch-Physikalisches Institut & Helmholtz-Institut Jena, Frauenhoferstr. 8.

Per term, one or two students may work on the project

The relativistic Euler equations are non-linear partial differential equations for the evolution of relativistic fluids, which can generically form shocks, where characteristic curves intersect. Certain numerical schemes designed to solve such problems require the equations to be written as conservation laws. Such conservation laws introduce a set of evolved "conserved'' variables, alongside the "primitive'' variables, which 
characterise the fluid from the perspective of a comoving observer. Both sets of variables are required to numerically evolve the system of equations, however the map from conservative to primitive variables cannot be written in a closed form. This requires a numerical solution to this problem. Historically this is performed with a root finding algorithm such as the Newton-Raphson method. In this project the student will investigate the use of machine learning techniques to solve this problem and compare their accuracy and speed to traditional methods.

Goals and Context

• Understand the Special Relativistic Euler Equations for relativistic fluid flow, and the relavance of conservative numerical schemes for shock capturing.
•  Achieve a basic understanding of thermodynamical equations of state for relativistic fluids.
•  Investigate the inversion of conserved fluid variables to primitive fluid variables through numerical techniques.
•  Solve the problem of conserved to primitive variable conversion for an ideal gas through the Newton-Raphson method.
•  Train a neural network to perform the same variable conversion.
•  Compare the performance and accuracy of the methods you investigate.

Methods:

The students will numerically convert a set of conservative variables to the corresponding primitive variables for a set of test data corresponding to an ideal gas, using first traditional root finding approaches, and then by training a neural network to perform the inversion. The project will proceed following a guided sequence of tasks:

• Study of the relativistic Euler equations, the Lax-Wendroff theorem, and the necessity of conservation law formulation.
•  Study of the ideal gas equation of state and the necessity of numerical
  conserved to primitive variable inversion.
•  Constructing a dataset of corresponding conserved and primitive variables.
•  Solution of the variable inversion problem using a root finding algorithm such as the Newton-Raphson method.
•  Training of a neural network on a training dataset, and testing its accuracy on a testing dataset.
•  Comparing the performance of the two above approaches in speed and accuracy.
•  Investigating improvements of the neural network approach through altering the network hyperparameters.

Python is strongly recommended as a coding language for this project due to the availability of machine learning packages such as PyTorch and TensorFlow.

Prerequisites:

•  Basic knowledge of numerical solution of algebraic equations
•  Basic programming skills
•  Basic knowledge of Machine Learning techniques helpful

Contact:

Person in charge: Prof. Dr. S. Bernuzzi

Supervision: Dr William Cook (`william.cook@uni-jena.de`)

Place: Abbeanum, Fröbelstieg 1

Per term, one or two students may work on the topic.

Possible topics within this project are:

• Entanglement and its entropy measures in quantum mechanics
• Supersymmetric quantum mechanics
• Magnetic monopoles and quantization of electric charge
• Magnetic monopoles in theoretical condensed matter physics: From the Berry phase in quantum mechanics to the field theoretical description of Weyl semimetals
• Do particles exist interpolating between a fermionic and a bosonic behaviour? Anyons and their description in terms of Chern-Simons theory.
• Hawking radiation and evaporating quantum black holes*
  
  *basic knowledge of general relativity and quantum field theory required.

Contact

Supervision: Prof. Dr. Martin Ammon

Venue: Theoretisch-Physikalisches Institut, Fröbelstieg 1 (Abbeanum)

One or two students may work on this topic per term.

Goals and context

Computational Fluid Dynamics (CFD) is a central part of computational physics and has been a driver for the development of modern numerical methods. It involves solving flow mechanical problems that cannot be solved analytically and are expensive to study experimentally by integrating generally nonlinear, partial differential equations.

In this project, the students will apply numerical methods to solve the Navier-Stokes-Equations for the case of an incompressible fluid to study flow within a cavity and flow around obstacles.

Methods

Timestepping schemes for integration of hyperbolic equations as well as a relaxation scheme for solving elliptic equations will be employed to solve the Navier-Stokes-Equations numerically on a staggered grid in two dimensions. The stability and convergence behavior of these schemes will be examinated.

The students will use C/C++, Python or Matlab to implement these methods.

Prerequisites

•  Basic knowledge of partial differential equations
•  Basic knowledge of numerical methods
•  Familiarity with at least one of the suggested programming languages

Contact:

Person in charge: Prof. Dr. Bernd Brügmann

Supervision: Praveer Gollapudi

Place:  Abbeanum, Fröbelstieg 1 or PAF Computerpool

Per term, one or two students may work on the topic

Compton scattering is the inelastic scattering of a photon on a free electron, in which a change in the wavelength of electromagnetic radiation is observed.The Compton effect is one of the cornerstones of quantum mechanics, which accounts for both wave and particle properties of light and matter. It is well known that the cross section of this process, described by the Klein-Nishina formula, depends on the energy and suggests that Compton scattering is very sensitive to the polarization of incident radiation. This sensitivity is the basis of Compton polarimetry, which is currently widely used for research in nuclear and atomic physics, for example in the Helmholtz Institute Jena.

While the standard Klein-Nishina formula is derived for the simplest case of light scattering by an electron at rest, in this project we investigate the case where the target electron has some momentum distribution. This so-called impulse (or momentum) approximation is a good approach for understanding the Compton scattering by weakly bound atomic electrons, which is required to analyze modern polarimetry experiments. In the proposed project, we will examine different models of electron momentum distribution and study how they affect the energy distribution and polarization of scattered photons. Our theoretical predictions will be compared with new experimental data, obtained at the PETRA III synchrotron in Hamburg

Goals of the project

•  Theoretical analysis of the Klein–Nishina formula and of its predictions
•  Derivation of the basic expressions of the impulse approximation
•  Investigating how the polarization of scattered photons depends on the energy and polarization of incident photons
•  Comparision of different theoretical models of momentum distribution and selection of the best approximation for modeling experimental results

Prerequisites:

•  basic knowledge of quantum mechanics
•  programming skills (Fortran, Mathematica, Pyton)

Contact:

Supervision:  Dr. Anna Maiorova (group Prof. Dr. Stephan Fritzsche)

Where: Theoretisch-Physikalisches Institut & Helmholtz-Institut Jena, Helmholtzweg 4

Per term, one or two students may work on the project

Goals and context

The strong coupling of light to quantum systems relies on the confinement of electromagnetic fields to sub-wavelength volumes. This can be achieved by hybrid nanophotonic quantum systems, in which photonic nanostructures support tightly confined electromagnetic resonances. Computer simulations are an essential part of this research since the fabrication of nanoscopic structures is challenging and the experimental characterization of optical fields at the few photon level with nanometer resolution is equally complicated. Therefore, reliable simulation methods are required to calculate the electromagnetic response of nanostructured matter in advance. Since we are dealing with structures in the sub-wavelength range, "rigorous" methods are needed, which solve Maxwell´s equations without any approximation. Different approaches have explored for certain classes of nanophotonic structures (micro and nano cavities, metasurfaces, nanoantennas).

Methods

The students will implement and use a rigorous numerical method (FDTD or FEM) for the solution of electrodynamic problems. They will either use one of the existing professional implementations of such methods or will be working on their own implementation in a programming language suitable for high-performance computing. The method will be used to simulate the behavior of a nanophotonic structure and to investigate the coupling to quantum systems.

Programming can be done in any language preferred by the students, but Python and Matlab are supported by existing implementations.

Prerequisites

• Basic knowledge of electrodynamics and related partial differential equations
• Basic knowledge of optics
• Basic knowledge of numerical methods
• Familiar with at least one programming language supporting numerical simulations (preferred Python or Matlab)

Contact:

Person in charge: Prof. Dr. Thomas Pertsch

Supervisor: Dr. Ángela Barreda

Place: Abbe Center of Photonics, Campus Beutenberg

Per term, one group of one or two students may work on the topic.

Goals and Context of the project

Quantum computers promise a runtime advantage compared to their classical counterparts for certain tasks. However, currently existing quantum devices operate with moderate numbers of qubits and are prone to errors due to experimental noise and decoherence. To show that quantum computers provide an actual advantage requires outperforming the best algorithms for simulating quantum dynamics on classical computer, which led to a race between scaling up quantum hardware and improving classical simulation algorithms.

The goal of this project is to build a classical emulator of quantum circuits and to use it to simulate one of the major quantum algorithms. Also, you will explore how to model noise and errors in quantum devices. The focus of the project can be adapted depending on pace and interests of the students.

Methods

•  Quantum gates, quantum circuit model, quantum algorithms
•  Open system dynamics simulation through quantum channels/Lindblad mater equation
•  Numerical methods for linear algebra: Sparse matrices, eigenvalue problems
•  Numerical solution of ordinary differential equations, numerical integrators
•  Visualization tools for numerical data
•  Use of libraries for quantum circuit emulation like qiskit, qutip etc.

Instructions will be provided in Jupyter notbooks with code examples in Python. If preferred, another programming language can be used.

Prerequisites:

Solid knowledge quantum mechanics

Basic knowledge of numerical methods

Familiarity with Python programming language and use of numpy/scipy libraries (or another programming language suitable for numerical simulation such as Julia, Matlab,...)

Basic knowledge of quantum optics is useful

Contact:

Person in charge: Prof. Dr. Martin Gärttner

Supervisor: Adrian Aasen, Prof. Dr. Martin Gärttner

Place: IFTO, Abbeanum

Per term, one group of one or two students may work on the topic.

Goals and context

• Basic concept of hyperbolic partial differential equations (PDEs) and the initial-boundary value problem (IVBP)
• Finite differencing methods for derivative approximation
• Method-of-line for time-domain PDEs with Runge-Kutta timesteps
• Numerical implementation of methods to solve multi-D PDEs
• Concepts of numerical stability and convergence

Methods

The students will solve the IBVP with the wave equation in 1+1 and 2+1 dimensions (one time dimension and one and two spatial dimensions) numerically. The project has different sequential steps:

• Wave equation and reduction to first order system
• Characteristic analysis and well-posedness
• Finite differencing approximation of derivatives and convergence
• Runge-Kutta time integrators
• Solution of IBVP withthe 1+1 wave equation and periodic boundaries using the method of lines
• Stability and convergence
• IBVP with open boundaries and Sommerfeld boundary conditions
• Wave equation with a potential: the Regge-Wheeler equation, scattering of graviational waves off a black hole and quasi-normal modes
• More spatial dimensions: the 2+1 wave equation

Students can code in their preferred language, although Python is strongly recommended (open sources, simple and optimal for visualizations).

Prerequisites

• Basic knowledge of partial differential equations
• Basic programming skills

Contact:

Person of charge: Prof. Dr. S. Bernuzzi

Supervision: 

Place: Abbeanum, Fröbelstieg 1 or PAF Computerpool

Per term, one or two or three students may work on the topic.

Context and goals:

In this project, mutual gravitational perturbations in systems containing stars, planets, and minor bodies are studied. Depending on the scenario and configuration, these perturbations can lead to different types of short and long-term phenomena: resonances and chaotic behavior as well as secular effects. Possible examples for specific scenarios include: capture in and release from orbital resonances; long-term stability of planetary systems; Lyapunov exponent and chaotic motion; influence of small perturbers on chaotic systems; secular perihelion drift in multi-planet systems; Kozai mechanism. For each specific problem, analytic approximations are available and can be used for comparison with the numerical results.

Methods:

 A handful of numerical integrators is available, covering a set of different algorithms (Bulirsch­-Stoer, Runge-Kutta, Everhart, (hybrid) symplectic) and scenarios. The integrators can be compared with respect to their precision and speed. Simulation results can then be visualized and statistically examined with self-made programs/scripts.

Instructor:    Dr. Torsten Löhne

Venue:          Astrophys. Inst. and Unisternwarte, Haus 2 (Schillergässchen 3)

The complex topic can be worked on by one or multiple students. The actual tasks will be adapted.

Stars are mostly born in open clusters and spend a significant part of their lives as members of a cluster. An open cluster contains dozens or hundreds of stars formed at nearly the same time from the same nebula and loosely bound by mutual gravitational attraction.

The supernova progenitors, massive stars, form in the cores of open clusters. Twenty percent of them are thought to be ejected due to the strong tidal interactions, while the rest remain inside the cluster. Although the massive stars undergo a supernova and die at young ages (<50 Myr), many well-studied supernova remnants (SNRs) are not directly linked to any open cluster despite the short (<100 kyr) maximum time passed after the supernova. This could be either because the cluster has not yet been detected or has already been dispersed, or the progenitor has been a runaway star and had already left the parent cluster. Yet, in the former two cases, the birth cluster can be discovered.

The cluster members share similar distance, age, metallicity, extinction, and velocity. Therefore, the differences in apparent brightness among members are due only to their intrinsic luminosities, thus their masses. The distances and the transverse velocities of the stars can be derived from the astrometric parallax and proper motion values, respectively, measured by the Gaia Satellite. The color-magnitude (Hertzsprung-Russell) diagram of the cluster members indicates the age, metallicity, and extinction. The most massive and hottest stars of the cluster evolve faster, move away from the main sequence in the color-magnitude diagram, and become cooler giants and/or supergiants. The position of the turn-off from the main sequence can be used to estimate the age of the cluster. To identify the properties of the members as well as the cluster variables, the color-magnitude diagram is fitted by a theoretical isochrone calculated for certain stellar evolution models and initial mass functions. However, the parameters determined by the isochrones must be tested by spectroscopic observations of the cluster members. The atmospheric parameters of the members derived from their spectra narrow the uncertainty of theoretical isochrones.

By detecting and studying the birth cluster, the SNR progenitor masses and metallicities can be found. This information is important to classify the SNRs and their neutron stars, if there are any.

This project aims to teach students how to determine the properties of the open clusters using astronomical catalogs, stellar evolution models, stellar kinematics, observations, data reduction, and analysis, as well as SNR and shock physics.

Tasks  

•  Searching for a positional link with the SNRs and the already known clusters through a catalog search
•  Selection of cluster members regarding their positional and kinematic properties
•  Setting the color-magnitude diagram of the clusters or loosely groups using optical and near-infrared photometry from various catalogs
•  Spectral observation, data reduction and analysis of the brightest members
•  Measuring the effective temperature, surface gravity and metallicity of the stars
•  Determination of the extinction, the cluster age, and the progenitor mass by the isochrone fitting.

Contact:

Supervisor: Dr. Baha Dincel

Location (night observation): University Observatory in Großschwabhausen

Location (data reduction and analysis): Astrophysical Institute, Schillergäßchen 2, Jena

The tasks can be worked on by up to 3 students