Measurement of the microm sized radius of Gaussian laser beam using the scanning knife-edge.

where co is the angular velocity of the chopper, r the distance from the rotating center to the laser beam axis, and t2-t, the time interval for a variation of P(x)/P0 from 0.9 to 0.1. Figure 1 shows the experimental arrangement. In this experiment, we use a He-Ne laser oscillating in the TEMoo mode. The wavelength is 0.63 m. The position of the beam waist is located at the output mirror of the laser oscillator, and the beam radius w, at the waist is 0.4 mm. The focal length of lens A is 367 mm. The distance from lens A to the output mirror surface of the laser is 600 mm. Lens A transforms the beam from the oscillator to a beam that has a more accessible waist. The radius and the posi-