A massive green laser in Uppsala

As I mentioned in my post yesterday, the “Allt ljus på Uppsala” (All lights on Uppsala) light festival is on at the moment, and yesterday evening I got my first chance to explore only some of the exhibits. Probably the coolest (both in effect and background) that I have seen so far is the monumental (seven hundred watts!!) 532 nm green laser shining all the way down Drottninggatan from the Carolina Rediviva library. On the library itself (off in the distance in my photo) is a rainbow effect of lights. The whole thing is a nod to Uppsala’s own Anders Ångström, who was one of the founders of the science of spectroscopy.

If you live in Uppsala and you haven’t checked it out yet, I do recommend it, it’s really quite impressive…

From the Allt ljus på Uppsala webpage (and translated by me to English, so excuse any errors):

Idea: 200 years ago this year the Uppsala physicist Anders Ångström was born (13th August, 1814). He was appointed Professor in Physics at Uppsala University in 1858 and came to develop the undergraduate education in physics. He was also rektor (chancellor) for the University between 1870 and 1871. Anders Ångström’s work has been described as groundbreaking. He was one of the founders of spectroscopic methods used in the study of light. Through studying light and the spectrum of rainbow colours which become visible to the eye when passing through for example a prism, can a light beam’s wavelength, frequency, speed and energy be determined. With the help of spectral analysis it is possible to analyse the sun and other celestial bodies, as well as to determine a star’s chemical composition and age. Anders Ångström, amongst other things, has given his name to a crater on the moon, the Ångström Laboratory in Uppsala and the length unit “Ångström”, which is one hundredth of a millionth of a centimeter (1 Å = 0.1 nm). He is buried in the old cemetery in Uppsala. Technology: The laser beam comes from a Laserimage DL G Beam module which thanks to the special optics produces a laser beam with extremely low divergence, which means that the beam is highly focused even at extremely long distances. The laser’s wavelength is 532 nm which is a green wavelength which the eye is extra-sensitive to, allowing it to be perceived as extremely bright. The laser is a semiconductor laser and draws only 700W and is air cooled, and can be compared to the old types of gas lasers which for the same effect would have required over 70,000 W and running water to cool the laser. The wall is illuminated with 8 LED luminaires which are equipped with 14 15W diodes from osram. If this setup had been made 10 years ago it would have required almost 90,000 W, today we can manage with only 2,400 W.