Lab Snapshot: Transverse Laser Modes
For the laser currently on the bench, the possible transverse electromagnetic modes aren’t all simple, smooth spots. While TEM00—the tightly focused, low-irregularity mode—is what many manufacturers force their devices to run at, other solutions exist with distinct patterns. The subscripts denote the number of divisions in the beam, though some of the higher-index labels are only guesses. One odd pattern appears to have radial rather than rectilinear divisions, and its exact classification is unclear.
The images were captured by projecting the beam through an enlarging lens onto a whiteboard—a crude approach that works surprisingly well. Contrast has been enhanced in the pictures; in reality, the beam is simply red.
