Abstract A helium-neon laser operating in two or more axial modes generates beat signals in the ultra-high frequency (UHF) range at a photodetector. An analysis of earlier data obtained at very low light levels shows that such UHF beats can be observed even when the mean time interval between the arrival of successive photons at the photodetector is greater than the period of the beat. This is because the beat is actually a sinusoidal modulation of a random carrier.