Abstract

Spontaneous emission into the oscillating mode of a laser is responsible for the well-known phase diffusion and Schawlow-Townes linewidth limit. Similar emission into higher-order transverse modes of a laser oscillating in a TEM₀₀ mode causes jitter in the beam axis. This jitter causes spatial noise that can be easily detected. The positional accuracy of the center of a laser beam is limited by the presence if vacuum fluctuations in the TEM₀₁ mode, even in the absence of fluorescence, leading to a fundamental limit on the pointing accuracy of a laser. When fluorescence is present, the spatial noise appears at beat frequencies between the fundamental and higher-order modes.

© 1988 Optical Society of America