LPT-9 Serial Experiments of He-Ne LaserSerial Experiments of He Ne Laser Description Through the adjustment of the He Ne laser, the length of the resonant cavity is changed, the change of the laser mode is observed and the practical ability of the students is trained. The confocal spherical scanning interferometer is used to allow students to measure the divergence angle of the He Ne laser. The spectral distribution of the transverse and longitudinal modes is observed directly.