LaserFest- Un'Idea Brillante! -University of Pavia, Italy
The realized exhibit was composed of 12 stands:
We showed the two videos containing the interview to Charles H. Townes. . The videos have been dubbed in Italian, and the dubbed version can be provided on request.
2. Properties of light, and differences between lamps and lasers light.
This stand was dedicated to illustrate the basic properties of light and to discuss phenomena like reflection, refraction, total internal reflection, interference and polarization. The installation included also an "experiments manual", so that the visitors could also realize them directly.
3. LASER sources:
On this stand it was possible to observe several laser sources, based on different active media: diode pumped solid-state lasers (Nd:YVO4), gas lasers (He:Ne), semiconductor lasers, and also a Nd-glass laser. Some of the laser sources could be switched on and operated, and were also used to show how the alignment of mirrors affects the laser mode sustained by the cavity. We also gave to the visitors the possibility to directly modify the LASER cavity, and to observe how it affected the laser beam properties. The Nd-glass laser source was disconnected from the power supply, and was used just to show the different structures of the LASER cavities, and of the pumping system. One of the semiconductor LASERS was put under a microscope, so that all the visitors could see its size and structure.
This part was dedicated to show two rainbow holograms and to explain how holograms can be realized, viewed and used. The holograms have been made available, for the period of the exhibit, by Prof G. Molesini of INOA (Istituto Nazionale di Ottica Applicata - National Institue for Applied Optics, Pisa, Italy).
5. Nonlinear optics:
By using a Q-switched Nd:YAG laser source (emitting at 1064 nm) we showed two nonlinear phenomena. The second-harmonic generation (producing green light) and the Raman scattering (yielding to the generation of red light). In particular we also discussed the use of optical nonlinear techniques for different applications.
6. Optical fibers
This stand was divided into three smaller parts. In the first one the Tyndall experiment is recreated, showing the possibility to guide light using water. In the second section the optical fibers are introduced, showing how they are created, their properties and the possible techniques to couple light into an optical fiber. The visitors also had the possibility to modify the different coupling stages, and to observe the differences between single-mode and multi-mode fiber coupling. In the final part of the stand we showed also the instruments used to remove the fiber coating and to cut and splice fibers.
7. Telecommunication systems
An example of fiber-optic telecommunication system was arranged, including: i) two VCSEL-based laser transmitters (one visible-red, the other infrared); ii) a large-core optical fiber; iii) a photodetector. The signal that was transmitted by intensity modulation was an analog video signal taken from a vidicon camera (a scene from the exhibit), and it was displayed onto a video monitor. The fiber was to be manually aligned by the visitors at both the transmitter and receiver side; when the alignment was OK the monitor displayed the camera image, otherwise the monitor picture was noisy.
8. CD-reader and bar-code reader
This stand was dedicated to show two lasers applications that are widely used during everyda's life. On one side we realized a schematic CD-reader, showing how the laser light reflected by the CD is detected and converted into a signal. To better illustrate this part we also realized a panel to explain the differences between CD, CD-RW, DVD and Blue-Ray. The bar-code reader was realized using a mirror, mounted on a motorized stage, and a semiconductor laser emitting red light. By opening the case containing the instrument it was possible to observe the turning mirror, the light source and detectors.
9. Distance measurement
Two distance measuring systems were on display. The first one was based on a commercial handheld time-of-flight telemeter, with an accuracy of 1 mm. The telemeter measured the position of a toy train travelling on a railroad track, while the position was graphically represented on the monitor of a PC interfaced to the telemeter. Another sensor, based on the principle of triangulation, was used to measure the profile of the train, which was displayed on the PC monitor alongside with the train position.
10. Vibrations measurement
Two special laser vibrometer instruments developed by the University of Pavia were used to demonstrate the capabilities of laser instrumentation to measure very small displacement with high accuracy. The two optical sensor heads of the first instrument were aimed at two small loudspeakers that were driven by audio signals of very low level, such that no sound could be heard from the two loudspeakers. The first laser was aimed at the loudspeaker membrane, and measured its displacement. The electrical signal generated by the instrument was a perfect analog replica of the displacement, and it was electrically amplified and supplied to another large loudspeaker, that reproduced the sound that was intended to be applied to the tiny loudspeaker. The second laser was aimed at the wall of a Plexiglas box that contained the other tiny loudspeaker, thus demonstrating that it can be possible to listen to people talking in a closed room by shining a laser beam on the window of the room. A third experiment used another laser vibrometer to measure the displacement of the rubber membrane placed at one end of a 5 meter long rubber tube. Visitors were invited to speak into the other free end of the tube. The vibration of the membrane was converted into an electrical signal by the laser vibrometer, and then supplied to the electrical power amplifier, and the visitor's voice reproduced by another large loudspeaker.
Different Biomedical applications of laser light and optical fibers were shown in this stand, including both research level applications and common commercial objects. In particular we had a laser-device for dentistry, a fiber-optic gastroscope, and an optical stretcher. In order to offer the visitors a high interactivity with the gastroscope, we realized a "dummy patient" with tubes and bifurcations, and inserting some small objects at the tube ends. The optical stretcher explanation took advantage of some panels and of a presentation, whose slides were cycling on a screen. The stretcher on display at the exhibit was also used for live demonstrations by experienced researchers.
12. Industrial applications
This stand was realized also thanks to the support we received from Orotig S.r.L. (an Italian company working on LASERS welding) which gave us the possibility to use, and show a laser welder during the exhibition. For safety reasons no visitor has been allowed to use the laser welder, but they could see what was happening inside the system, and they were encouraged to test the strength of the realized weld.
Thank you to the LaserFest-PV team for all your great work!