LE-0300 HeNe-Laser, advanced

The humble Helium Neon (HeNe) laser still has many applications, due to its superior beam quality and coherence. In all physics text books this laser represents the class of the gas laser and was the first gas laser invented by Ali Javan in 1960 right after Theodore Maiman demonstrated the first operation of the ruby laser. Since the HeNe laser was continuously operating and easy to build in a laboratory it served as specimen for a lot of scientific work and proof for theoretical predictions. It starts with the theory of optical resonator, Doppler broadened laser active material in a cavity, spectral hole burning (Lamb dip), single mode operation, coherence and intra-cavity absorption (inverse Lamb dip) just to name a few. For technical applications the HeNe laser is still in use due to its outstanding beam quality and coherence as secondary meter standard and is present in each air plane or ships as laser gyroscope for navigation. This experiment is designed as an open frame setup in such a way that all components can be arranged freely on a stable optical rail. A Helium Neon tube with Brewster windows on both ends is used to perform a variety of fundamental experiments. Verification of mode selection properties, the optical stability range and the ABCD matrix formalism of the cavity used are discussed. A birefringent filter as well as a Littrow prism is used for the wavelength selection and the effect of an etalon used inside the cavity are investigated. A photo detector for measuring the relative output power and an alignment laser are supplied with a 1 meter long optical rail, along with all necessary mounts and adjusters. For the visualization of the mode structure a „Fabry Perot“ extension is available or an electronic spectrum analyser is used to measure the modes beat frequency. The optical resonator is formed by two precision adjustment holders for common 1/2 inch exchangeable mirrors having different radii of curvature. For ease of adjustment, at the beginning a "green" pilot laser is attached as an alignment aid. The laser tube is mounted into XY-adjustments to align the tube with respect to the pilot laser.