Researchers have developed a new decoding method for orbital angular momentum (OAM) holography. Based on cross convolution, it significantly exceeds the upper limit of OAM holography’s information extraction rate. They designed an amplitude-modulated pattern called Amplitude Decoding Key (ADK) as a decoder for information extraction in OAM holography, starting with the spatial frequency domain. A cross-convolution result is obtained by converging a series of spatial frequency components of the amplitude decoding key and the OAM-multiplexing hologram.
The researchers developed a new cross-convolution theorem for successfully extracting information from OAM-multiplexing holograms. When the cross-convolution theorem is satisfied, the corresponding OAM-encoded holograms can be decoded independently or parallelly by a spectral component or multiple spectral components of the ADK. The amplitude-modulation-based decoding method can be realized using a digital micromirror device (DMD) and operating at a frame rate of several kilohertz. It results in a two-orders-of-magnitude increase in the information extraction rate in orbital angular momentum holography.
In addition to the high information extraction speed, the scheme can support information extraction at any desired position corresponding to a specific spatial spectrum component and parallel reproduction of images at different positions by simultaneously employing multiple spatial-spectral components. The new technique will have promising applications in high-speed holographic display and wireless optical communication.