Principle
The difference between spontaneous and stimulated emission of light is demonstrated. The beam propagation within the resonator cavity of a He-Ne laser and its divergence are determined, its stability criterion is checked and the relative output power of the laser is measured as a function of the tube's position inside the resonator and of the tube current.
Benefits
- Set up and run a laser, that is by now classic, from its constituting elements
- Get a feel for the delicate adjustments necessary to achieve lasing conditions
- Dicover the way many parameters can influence the output of this gas laser
Tasks
- Set up the He-Ne laser. Adjust the resonator mirrors by use of the pilot laser (left mirror: VIS, HR, plane; right mirror: VIS, HR, R = 700 mm).
- Check on the stability condition of a hemispherical resonator.
- Measure the integral relative output power as a function of the laser tube's position within the hemispherical resonator.
- Measure the beam diameter within the hemispherical resonator right and left of the laser tube.
- Determine the divergence of the laser beam.
- Measure the integral relative output power as a function of the tube current.
The He-Ne laser can be tuned using a BFT or a LTP.
Learning objectives
- Spontaneous and stimulated light emission
- Inversion
- Collision of second type
- Gas discharge tube
- Resonator cavity
- Transverse and longitudinal resonator modes
- Brewster angle