A lightsaber is a fictituous fencing weapon from the "Star Wars" Universe of the movie franchise of the same name created by film maker George Lucas. There have been numerous discussions throughout the years whether one could build a real lightsaber. This motivated Professor Tobias Brixner to give a public lecture including experiments within the event series "Physics on a Saturday" on May 5, 2018, at the University of Würzburg. There, a lightsaber is realized on the basis of femtosecond laser pulses. The video "Femto Stars" is a short summary for those in a hurry; the complete lecture, including scientific explanations, is accessible further below.
Are lightsabers pure fiction? Most people argue that a laser beam propagates unhindered until it hits an obstacle, and therefore spatially limited lightsabers are physically impossible. The film "Femto Stars" and the photo in the header of this page show that you can apparently produce light effects of finite length. How does this work? What is it good for?
The recorded lecture "From Lightsaber to Femtochemistry - Fiction and Applications with Ultrashort Laser Pulses" (available with German or English subtitles), which can be accessed below, uses an analogy with music to show how ultrashort laser pulses are created. Turning light on and off in just a few femtoseconds (i.e., millionths of a billionth of a second) opens up a whole new world of opportunities to track and even control extremely fast physical processes in real time. The reality even surpasses the "Star Wars" fiction, because in our research we penetrate with precision down to the atomic level and "cut" chemical bonds in a molecule in the context of "quantum control". In addition to this "femtochemistry" one can use ultrafast spectroscopy, for example, to temporally resolve the biological processes of photosynthesis or vision. A specialty of our research group is multidimensional spectroscopy, which provides comprehensive information. Femtosecond laser pulses are also used in medicine, for example in the "femto-LASIK" eye surgery, whose functional principle is based on the "lightsaber" effect.
The lecture provides an introduction to the basics of ultrafast spectroscopy and, at the same time, the scientific background for the lightsaber of "Femto Stars" (full-screen version available by clicking in the upper right corner of the video).
The pioneering work on the "lightsaber" mentioned in "Femto Stars", i.e., filamentation in air
How to use a "lightsaber" atomically precise in a review article on quantum control
Manuscript of the Nobel Prize lecture by Ahmed Zewail, the pioneer of femtochemistry
Nice introduction to femtosecond lasers and spectroscopy
Original work on the time resolution of the process of vision in the eye
- Pioneering work on multidimensional spectroscopy of photosynthesis
There are many suggestions on how to build a lightsaber on the internet, especially on YouTube. The following selection has nothing to do with femtosecond lasers. Make your own judgment of how successful these trials are. If you would like to work with the "Femto Stars Lightsaber," you should become part of our team, as we use filaments in research daily to create broad spectra...
- Illuminated plastic cover: Prop with beautiful look, but made of ordinary material, without cutting functio
- Focussed laser beams: Propagation length not limited
- "Evanescent field" through small holes: Range only a few wavelengths, so a few microns, rather than ~ 1 meter
- Plasma through holes of a ceramic rod: solid material required inside the lightsaber, brittle ceramic, hot grip
- Spark discharge between metal wires: no continuous light effect, metal wires on the edge required, no cutting function
- Red-hot metal rod: solid material in the center, can start melting process
- Burning methanol liquid jet: no actual cutting function, but local fire production