Experiment: Determination of the spatial properties of laser beams

In this lab, the spatial properties of beams from two types of lasers are quantified and their profiles are obtained using the so-called "knife-edge" method. The experimental results are used to determine the radius, divergence, Rayleigh length, and the M2 quality factor of each source. Topics covered: - Optical power, intensity, and energy density - Size and divergence angle of the laser beam - Measurement of the beam profile of a semiconductor laser (DPSS) and a diode laser - Knife-edge method and study of beam modification by a lens - Dependence of beam profile on axial position Z with the "knife-edge" method - Beam parameters, Rayleigh length, and determination of the M² quality factor Principles and objectives: The main parameters of a laser radiation are the beam radius or diameter, its divergence angle, and the Rayleigh length. These quantities allow the determination of energy density. Measuring the dimensions and exact position of the focal point as well as the beam quality factor M2 are fundamental for optimizing existing laser systems and developing new ones. In this lab, the spatial properties of beams from two lasers are quantified and their profiles are obtained using the "knife-edge" method. The two sources studied are: a diode-pumped semiconductor module and a diode laser. For a TEM00 radiation, the intensity distribution is Gaussian in the transverse plane and the M2 quality factor quantifies the deviation of a laser beam from a Gaussian beam. Furthermore, the higher the beam divergence and the smaller the Rayleigh length, the higher this quality factor. Based on the experimental data, the M2 quality factor of the beams from the two lasers is determined.

Composition:
▪ 1 optical rail 0.5 m, with graduated ruler
▪ 1 green DPSS laser diode mounted on a rider
▪ 1 red laser diode
▪ 1 laser diode controller
▪ 1 focusing optic with rider support
▪ 1 "knife-edge" measurement system with rotary support on rider
▪ 1 collimation optic with rider support
▪ 1 photodiode with rider support
▪ 1 neutral density filter in mount
▪ 1 digital multimeter
▪ 1 set of experiment instructions (in English)