He-Ne Laser
For Student Groups
Open He-Ne laser systems are assembled from individual components and adjusted during the course. Doing this, the participants experience hands-on the fundamental principles of the laser technique.
- Age
- 16 to 21 years
- Duration
- 0.5 day
- Maximum number of participants
- 9
Experiments
- Characteristic emission lines from helium and neon in subjective observation
- Polarization of the laser radiation
- Fine adjustment of the laser mirrors
- Determination of the lasers wavelength and frequency
- Measuring the beam profile
- Quantifying the beam divergence
The fundamentals of laser physics are discussed. The focus lies on the light-matter interactions necessary for the laser principle. Subsequently, the working principle of a laser resonator is explained using the open He-Ne laser systems. At the He-Ne gas lasers, numerous characteristic emission lines from helium and neon are observed. Only one of these lines is amplified: the laser emits monochromatic light with a wavelength of 633 nm. The open setup of the laser systems allows a direct view on the Brewster windows revealing the polarization of the laser light due to reflection. The orientation of the polarization can be predicted and checked with a polarizing filter. Using a micrometer translational stage the laser beam profile is measured precisely and is compared to the expected Gaussian beam profile. The beam diameter is measured at different positions inside the resonator allowing a quantitative assessment of the very low beam divergence. The wavelength of the laser radiation is determined with a diffractive grating with a precision of plus/minus one percent.
Keywords
Structure of atoms: charged particles, electron shell, nucleus; light as electromagnetic wave