Published: | By: Ira Winkler
Photonics West is THE international highlight of the optics and photonics community, which attracts leading scientists and industry representatives to San Francisco every year at the end of January to discuss the latest developments.
Philipp Gierschke (Fiber & Waveguide Laser / Fraunhofer IOF), Mathias Lenski (Fiber & Waveguide Laser) and Gonzalo Palma Vega (Fraunhofer IOF) convinced the conference committees with their innovative research contributions on high-power lasers in the 2-µm wavelength range. Their work makes an important contribution to the further development of laser technology and opens up new possibilities for applications in spectroscopy, materials processing and the semiconductor industry
Philipp Gierschke – 3. Platz „Best Student Paper Award“ in Frontiers in Ultrafast Optics
Philipp Gierschke was honored for his work “100 W-class, mJ-level, few-cycle source at 1.9 µm wavelength”. His research focused on the development of novel fiber laser sources in the 2-µm wavelength range - a field with enormous potential that has hardly been researched to date. In particular, he dealt with the power scaling of such ultrashort pulse (USP) lasers; more precisely: the subsequent shortening of the pulse duration to a few optical cycles (few-cycle).
The core of the research is the development and experimental demonstration of a so-called non-linear multipass cell - a type of optical resonator - with which world record output parameters were achieved in combination with a 2 µm ultrashort pulse fiber laser. “The main challenge was the right choice of high-performance optics and their coatings for stable operation, as there are no ‘standard’ components for these pulse durations or laser power classes,” says Philipp Gierschke, describing the essence of his work and emphasizing that this achievement is a team effort, for which he received the award on behalf of the team.
By using 2µm USP lasers, the conversion efficiency of secondary sources can be significantly increased compared to 1µm wavelength driver lasers. These secondary sources make it possible to enter new wavelength ranges, e.g. into the soft X-ray range. This is particularly interesting for spectroscopy, microscopy of biological samples or to achieve even finer resolution. As the generation of secondary radiation is characterized by losses, the aim is to scale the power of the driver lasers - in this case the 2 µm USP laser.
Another application is the direct in-volume processing of silicon, which is of great interest to the semiconductor industry.
The award was presented at the “Frontiers in Ultrafast Optics” sub-conference, where he beat off the competition with a 4-minute pitch talk.
Mathias was already honored for his research results at this conference – so he could repeat his success. This time the jury was convinced by his contribution “Pump noise transfer in a highly efficient, in-band pumped thulium-doped fiber amplifier”.
Mathias Lenski and his colleagues are researching new ways to make thulium-doped fiber lasers more efficient and powerful. These lasers have great potential for applications with high power and high pulse energies. Normally, they are “pumped” with light at 793 nm, that means supplied with energy. However, a lot of energy is lost as heat, which poses technical challenges.
One promising alternative that has been investigated is the use of special Raman fiber lasers as pump sources. These operate at a wavelength of 1692 nm and are more efficient. However, they generate small power fluctuations that can potentially be transferred to the amplified signal. In his studies, Mathias Lenski is comparing this new pumping method with the conventional variant at 793 nm to find out which technology is more suitable.
This research is particularly relevant for high-power lasers in the 2-µm wavelength range. Those are used in material processing, sensor technology and in the generation of special light waves, e.g. in the mid-infrared or EUV range. By adjusting the pump wavelength to approx. 1700 nm, the efficiency can be significantly increased.
This offers enormous scaling potential for such a technology. The increased efficiency leads to less energy loss and enables more powerful lasers with new application possibilities. This makes them particularly valuable for secondary applications in which high-power lasers serve as light sources - from precise material processing methods to basic research in physics.
The award was presented in the sub-conference “Fiber Lasers XXII: Technology and Systems”.
Publication:
M. Lenski et al., Opt. Lett. 49, 4042 (2024).
PaperExternal link auf SPIE
st
Gonzalo Palma Vega received the award for his work “Comparison of TMI thresholds in non-PM and PM Fibers”. In it, he investigates transverse mode instabilities (TMI) in different fiber architectures.
Gonzalo Palma Vega received the award for his work “Comparison of TMI thresholds in non-PM and PM Fibers”. In it, he investigates transverse mode instabilities (TMI) in different fiber architectures.
The work investigates the thresholds for thermally induced mode instability (TMI) of two glass fibers with a large mode area: a polarization-maintaining (PM) and a non-PM fibre. Both were tested under identical conditions.
The TMI threshold indicates the power at which the laser beam becomes unstable and its quality suffers. The PM fiber shows a TMI threshold of 300 W along the slow axis, while the non-PM fiber reaches 330 W. The difference of 10 % results from mechanical stresses in the PM fiber, which changes the refractive index, among other things.
“However, the TMI threshold of the PM fibre can be significantly increased if the polarization direction is adjusted. This shows that PM fibers can offer advantages in suppressing mode instabilities despite an initially lower threshold,” explains Gonzalo Palma Vega and points out that these results have implications for the use of ultrashort pulse lasers in industry and science.
Publications:
G. Palma-Vega et al., Opt. Express 31, 24730-24738 (2023).
G. Palma-Vega et al., Opt. Express 31, 41301-41312 (2023).
Paper auf SPIEExternal link
We congratulate our scientists and look forward to further exciting research results!