From the Michelson interference of He-Ne laser beam, it is found that the coherence length of the beam decreases with the decrease of intensity when the laser beam passes through a nonselective absorption filter and the intensity becomes low enough. The effect can be explained by using the discrete wavelet structure model of classic plane light waves.
In this letter, the wavelet transform is used to decompose the classical linearly polarized plane light wave into a series of discrete Morlet wavelets. It is found that the energy of the light wave can be discrete, associated with its discrete wavelet structure.It is also found that the changeable energy of a basic plane light wave packet or wave train of wave vector $mathord{buildrel{lower3pthbox{$scriptscriptstylerightharpoonup$}}over k} $ and with discrete wavelet structure can be with the form of ${H_{0k}} = n{p_{0k}}omega$ $(n = 1,2,3,...)$, where $n$ is the parameter of discrete wavelet structure, $omega $ is the idler frequency of the light wave packet or wave train, and ${p_{0k}}$ is a constant to be determined.This is consistent with the energy division of $P$ portions in Planck radiation theory, where $P$ is an integer. Finally, the random light wave packets with $n=1$ are used to simulate the Mach-Zehnder interference of single photons, showing the wave-particle duality of light.
