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Optics & Metrology Systems

Ansprechpartner: Dr. Ferdinand Bammer

Applications of new optical elements and the development of innovative laser sources. Main topics are:

Laser-assisted Forming

Ellipsometry

Polarization-modulation

Pulsed Lasers

Contact:  Ferdinand Bammer.

 

 

 

Laser-assisted Forming

We develop forming processes assisted by local heating with laser radiation. By integration of diode-lasers into the forming tools brittle materials can be processed. We have experience with Mg- and Ti- alloys, high-strength-Al-alloys and high strength steels.

Laser-assisted bending and embossing needs small optics and lasers, which needs to be built into the bending machine. The current solution uses high-power laser bars, initially built for pumping disc lasers.

Bending-press.
Laser-assisted bending.
Diode bars.
Mg-sheet metal: cold and warm bent.
Beam paths in the lower bending tool.

Single Crystal Modulators

A SCPEM (Single Crystal Photo-Elastic Modulator) is based on a piezo-electric crystal, which is excited resonantly. This allows a very strong polarization modulation with small voltage-amplitudes around 5V.
With a polarization filter a strong transmission-modulation results, which can be used for different applications, like time-multiplexing, pulse-picking, laser-pulsing, and ellipsometry. Typical materials are LiTaO3, LiNbO3.

LiTaO3-crystal (30 x 9 x 4mm, basic frequency 90kHz) in laser-resonator
LiTaO3 in divergent RGB-Light between crossed polarizers.
Stretched LiTaO3 in divergent RGB-Light between crossed polarizers.

Ellipsometry

This is a method for surface characterization and determines the polarizing properties of the sample. With a mathematical model certain parameters, like film-thickness or refractive-index, can be calculated from the measurement. This method is very fast and is based on polarization-modulation or -switching with a SCPEM. It enables the acquisition of thickness-distributions within ms and is aimed to be used in-line for quality-control.

Inline 2D-thickness-measurement with stroboscopic ellipsometry.
Inline measurement of thickness-distribution of PEDOT on PET-foil with stroboscopic ellipsometry.

Pulsed Laser

We are focused on SCPEM-pulsed lasers which are emitting quasi-continuously with a PRF of 0.1-1MHz and can be used as a continuous laser beam, with special properties due to the high peak power of the pulses. This is realized with an SCPEM in the laser cavity. Best values are 60W average power with peak powers of 10kW emitted in the diffraction limited beam of a rod laser.

Pulsed Nd:YVO4-Laser with internal SCPEM.
Pulse sequence.