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The Leibniz-Institut für Kristallzüchtung (IKZ) is one of the leading institutions in the field of growth of crystalline solids. These play a fundamental role in photovoltaics, micro-, opto- and power electronics, sensor technology, optics and laser technology. Our work covers the full spectrum from basic over applied research up to pre-industrial development. The institute is part of Forschungsverbund Berlin e.V. ( and a member of the Leibniz Association ( More details can be found at the institute webpage:

We are currently looking for a

Master student (m/f/d)

for the topic:

“Laser cooling of solids in the 2-µm spectral range”

Laser cooling of solids is a recent emerging technology enabling to cool solid materials down to cryogenic temperatures by laser excitation. The cooling process is driven by anti-Stokes fluorescence which annihilates lattice vibrations, i.e., phonons. This novel technology is demanded for ultra-compact cryocoolers for space applications and self-cooling solid-state lasers. So far, rare-earth-doped fluoride crystals have been recognized as efficient laser cooling media, and ytterbium (Yb) is currently the representative cooling ion. State-of-the-art Yb:LiYF4 crystals were successfully cooled below 100 K by high-power laser excitation at 1 µm.

The aim of this master program is to study laser cooling of thulium (Tm)- and holmium (Ho)-doped fluoride crystals. These materials, known as laser crystals for the 2-µm spectra range, potentially provide laser cooling efficiencies twice higher than Yb-doped materials excited at 1 µm. Despite the potential of laser cooling at 2 µm spectral range, this topic has not yet been investigated in detail owing to the lack of powerful, wavelength tunable, and relatively narrowband sources around 2 µm.

The candidate will perform research activities in two research institutes: The Leibniz-Institut für Kristallzüchtung (IKZ, Berlin, Germany) and the French-German Research Institute of Saint-Louis (ISL, Saint-Louis, France, ( The IKZ is a unique research institute specialized for the science and technology in crystal growth. Growth and characterization of crystals will be performed in the junior research group ‘Fluoride Crystals for Photonics’ at IKZ. The ISL is highly experienced in laser technology in the 2-µm spectral range. Laser cooling of the grown crystals will be investigated using a state-of-the-art widely tunable laser source at 2 µm. The research stay at ISL will be financed by the institutes.

This master thesis involves the following tasks:

  • Growth of high-quality fluoride single crystals doped with Tm and/or Ho ions (at IKZ)
  • Spectroscopic characterization of the grown crystals for a wide range of temperatures (at IKZ)
  • Laser cooling characterization using laser sources emitting in the 2-µm spectral range (at ISL)

The candidate must have a Bachelor or an equivalent degree in physics, materials science, or a related discipline. Because of the international team, good English language skills are prerequisite.

For information about the project contact:

Dr. Hiroki Tanaka (IKZ),, Phone +49(0)30 6392 2821

Have we aroused your interest?

Then apply directly by clicking on the “Apply online” button below with a letter of motivation, curriculum vitae and all relevant certificates.

We look forward to receiving your application!