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Quantum technologies

Dieter Meschede's research group
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Master's theses (modules phys910/920/930)

Research projects for master students are divided into two parts: during the first 6 months, the student must scientifically explore the master's thesis topic (module Physics910), plan the project and develop the required research methods (module Physics 920). A short report (2-4 pages) on the exploration and the planning must be handed in. The last 6 months of the research project are reserved to the master’s thesis work itself. The master’s thesis has in general 30 to 60 pages. The results of the master’s thesis are presented in a talk near the end of the research phase. The formal aspects are summarized in the Module-Handbook Master in Physics.

The research topic of the master's thesis will be discussed together with the candidate. It is possible to bring in your own ideas. Examples of research topics are listed below. Other opportunities are also available and can be discussed in person in confidential terms. Please come and talk to us. We look forward to your enthusiastic participation.

Those who are interested to join our group, please contact:

Optimized Faraday Rotators for Applications in Photonics (08/02/19)

There is significant interest in reducing size and cost of Faraday Isolators, key components in high performance laser diode laser systems, and a basic question is: what permanent magnet configuration optimizes ∫Bdz? This project comprises an innovation project with industrial relevance and addresses the theoretical solution of the basic optimization task, analysis of cost and technical constraints and realization of a practical device.

Requirements: Master specialization in quantum optics/photonics; interest in computer simulations for applications in photonics and their experimental realization; interest in contacts to research within the industrial world.
Background: Diode lasers are sensitive to backscattered light. Spectral performance suffers already at return levels of 10-3. A well-known concept is the usage of optical diodes, known as Faraday-Isolators. An axial magnetic field acting on the Faraday rotator crystal makes the polarization rotate 45°, and the rotation is always clockwise as seen in propagation direction. Recent progress in manufacturing technology and permanent magnet configurations have led to improved designs with smaller footprint. Several configurations have been discussed, however no systematic evaluation of a permanent magnet configuration has been performed.
Questions this thesis seeks to answer: Which spatially restricted (box or cylinder) permanent magnet configuration maximizes ∫Bdz? This question has already been addressed for the simple cases, and analytical solutions were presented. The cylindrical symmetry of the actual problem motivates investigation of an analytic solution. If this turns out not to be feasible, a numeric optimization shall be performed. They shall give an answer to questions like: how to theoretically arrange NdFeB M52 permanent magnet material with 1.4 T magnetization to achieve 45° Faraday rotation with TGG crystals with minimum footprint? What is the dependence upon changes of the restricting length and diameter? How to balance cost vs performance?
Reference persons: Prof. Dr. Dieter MeschedeThis e-mail address is being protected from spambots. You need JavaScript enabled to view it
Image: Faraday isolator concept (adapted after SDM Magnetics).
What you will learn: Magnet physics and photonics, software based optimization with ie COMSOL Multiphysics, cooperation with industry.
Field of research: Photonics / Quantum optics / Quantum Technology
Literature:
[1] V. Frerichs, W. G, Kaenders, and D. Meschede: Analytic Construction of Magnetic Multipoles from Cylindric Permanent Magnets, Appl. Phys. A 55, 242 (1992).
[2] Gérard Trénec, William Volondat, Orphée Cugat, and Jacques Vigué: Permanent magnets for Faraday rotators inspired by the design of the magic sphere, App. Opt. 50, 4788 (2011).

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