Lasers

  • Study of the transverse intensity profile of a laser beam (He-Ne or laser diode): demonstration of the Gaussian profile, measurement of the beam width. This can be done by directly recording the profile on an interfaced CCD bar, followed by computer data processing. Alternatively, the intensity measured by a large-area detector placed behind a razor blade moved step by step (or an optical chopper) can be recorded. In this case, the beam profile is obtained by integrating the signal using data processing software. The variation in beam width as a function of propagation distance allows the divergence and position of the beam waist to be obtained (see Caliens notice).
  • Measurement of beam divergence and waist. The last experiment is performed at different distances from the laser cavity.
  • Application to the study of beam transformation by lenses.
  • Structure of He-Ne laser radiation
  • Temporal coherence: interference with very large walk differences (of the order of 1 m), using a Michelson interferometer assembled by the student. Estimation of a minimum value for the temporal coherence length of a HeNe laser. Case of a pulsed Nd:YAG laser: estimation of the pulse duration. Laser diode: observation of the longitudinal mode structure with a Michelson interferometer (observation of beats in the interferogram) and with a Fabry-Pérot interferometer.
  • Measuring the light output of a laser. Safety classes.
  • Diode-pumped Nd:YAG laser: introduction to laser operation (semiconductor and neodymium-doped YAG) and nonlinear optics (frequency doubling).
Published on March 13, 2017
Updated on March 13, 2017