Today lasers have great importance in measurement technique, medicine, material processing und science in general. At XLAB we have two open laser systems that are build up and adjusted from single components. By doing this the students learn hands-on the fundamental principles of laser technique.
At a Nd:YAG solid state laser the properties of the pumping diode can be investigated to optimize the wavelength according to the energy level system of the active medium and the mean life time of the upper laser level can be measured by means of an oscilloscope. With an infrared converter screen the IR-laser light can be made visible and we can measure the wavelength with a diffraction grating. When a special crystal is set inside the resonator, frequency doubling is produced as a nonlinear effect. In terms of photons this means that one ‘green’ photon with 532 nm wavelength is created out of two IR-photons! Now the transversal electromagnetic modes can be observed very well.
Our second laser is a Helium-Neon gas laser. When you look at the laser tube through a diffraction grating you will see the impressive spectral lines of Helium and Neon; the HeNe itself emits 633 nm.
The open set-up allows to look at the Brewster windows and the students can test the corresponding plane of polarisation of the laser beam with a polarising filter. With a micrometer shifting device you can measure the beam profile very precisely and you will get a fine bell-shaped Gauss curve. With a sliding calliper we can measure the diameter of the beam at different positions inside the cavity and determine the very small divergence of the laser beam.
In addition there are experiments concerning luminescence and polarisation. As an application of laser technique the students can perform measurements at a Michelson interferometer.