Determining the waist radius of a focused Gaussian laser beam using a millimeter-scale ruler

摘要

We present a simple and inexpensive method for determining the waist radius of a focused Gaussian laser beam. This method is motivated by the fact that if you focus the laser beam using a lens, the distance from the lens to the waist will vary slightly as the lens is moved along the beam-propagating direction. We show how the waist radius can be calculated from four large longitudinal lengths, measurable using a conventional millimeter-scale ruler. Analyzing the dependence of the calculated waist radius on these four measured lengths numerically shows that the accuracy of the calculated waist radius is mainly affected by the error in the relative shift in the distance from the lens to the waist position. The calculated waist radius for a real HeNe laser is close to the one measured. directly using a commercial beam profiler with an error within 7%.