New design for opto-mechanical components

As part of a semester project, Beat Fleischlin from mechanical engineering, successfully developed a new design for opto-mechanical components that can be used on an optical rail system. The mechanical components were designed such that they allow easy alignment of optical components. In our specific case, the opto-mechanical components were used in a diode-pumped solid state laser. Moreover, the handling of the components is convenient, they can be combined easily with other elements, and they consist of as many similar parts as possible for cost effective production.
Congratulations for your excellent design, Beat Fleischlin!
OptoMech_3 OptoMech_1

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Bending Laser Beams

Can a light beam be bent? Einstein said that light is affected by gravity and bent in the proximity of a large mass (general theory of relativity). Well, that’s not an effect that one can easily observe in everyday life. However, there is another way to bend light, namely when light travels through a medium with a refractive index that changes smoothly. In the picture below a green laser beam enters a water tank. The water is colored with fluorescein to make the laser beam visible from the side. The water in the bottom part of the tank has a higher refractive index because of added suger. The interface between the sugar water in the bottom part and the sugar free top part is smooth. When the laser beam enters the region of changing refractive index, the top part of the laser beam travels at a higher speed than the bottom part (low refractive index = high speed of light). Therefore, the wavefront of the laserbeam is continuously changing the direction towards the higher refractiv index region (sugar water).
This effect demonstrated below is not just fun to observe but is actually used in optical fibers. So called graded index (GRIN) fibers have a refractiv index that is high in the fiber core and that changes gradually with increasing radius. When light enters the fiber it is always bent towards the fiber core and, therefore, is guided by the fiber. The advantage of GRIN fibers over step-index fibers is siginificantly reduced modal dispersion.

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Congratulations Marc Labudde!

Marc Labudde successfully defended his bachelor thesis. Congratualtions! Marc developed a stabilized laser driver that will be used in a diode-pumped solid state laser (DPSS laser). The laser driver controls the current and temperature of a InGaN laser diode that emits at 444 nm. The 1 Watt beam of the laser diode is focused on a Pr:YLF crystal that itself is part of a laser cavity and produces a laser beam at a wavelength of either 639 nm (red) or 604 nm (orange). This DPSS laser is very colorful and lends itself well for being used for classroom and outreach demonstrations. The development of the stabilized laser driver was a project in collaboration with Prof. Ursula Keller and PhD student Christian Zaugg from the Ultrafast Laser Physics Group at ETH Z├╝rich, Switzerland.

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Upconverting Dye-Doped Polymer Nanoparticles

Last year, I was working on a project with Yoan Simon from the group of Christoph Weder at the Adolphe Merkle Institute. This research institute is located in Fribourg, which is in the French speaking part of Switzerland. At the Lucerne University, we performed the optical characterization of the low-power upconverting dye-doped polymer nanoparticles that were developed in Fribourg. The collaboration was very interesting and successful and resulted in a publication in the Journal Macromolecular Rapid Communications (check my Publications page).

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Radioactive Waste

The lecture topic was nuclear energy, radioactivity, and radioactive waste. The interesting outcome of a student discussion: Government should decide for a deep final repository for high level radioactive waste based on geological/scientific reasons and then carry it through. Since nobody wants to have it in the neighborhood anyways, political aspects should not even be considered.

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Last Swim?

It might have been my last swim in the Vierwaldst├Ąttersee for the season. The water was great – maybe a little nippy. My usual half km swim was doable but a hot shower a must. With a cold front in the forecast I’m wondering whether the beginning of fall will be the end of the swim season. Hopefully not – it’s just so wonderful to go for a quick swim at the end of a day!

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