Flat storage is running out of room, and researchers say they have found a way to pack far more data storage into the same space by writing it in 3D.
A team led by Fujian Normal University in China has developed a holographic data storage method that records and retrieves information by combining three properties of light, amplitude, phase and polarization. The work, published in Optica, shows the technique can increase how much information is stored while also making it easier to retrieve.
Traditional storage systems write data onto flat surfaces such as hard drives or optical discs. Holographic data storage works differently. It embeds information throughout the volume of a material using laser light, creating multiple overlapping light patterns within the same space. The researchers said this can significantly increase storage capacity and enable faster data transfer.
“In conventional holographic data storage, data encoding typically uses one light dimension such as amplitude or phase alone, or, at most, combines two of these dimensions,” said research team leader Xiaodi Tan from Fujian Normal University in China. “Based on the principle of polarization holography, we used a deep learning architecture known as a convolutional neural network model to enable the use of polarization as an independent information dimension.”
The team said light has multiple properties that could be used to carry more data, but combining them effectively has been difficult in practice. To deal with that, the researchers refined a method called tensor-based polarization holography, which preserves the polarization state of light during reconstruction. They said this makes polarization a dependable channel for storing additional information.
In holographic storage, information is saved as image-like data pages created by laser light patterns. Encoding converts digital data into these pages, while decoding translates them back into usable information.
Building on their earlier work, the researchers created what they described as a 3D modulation encoding strategy. By adjusting the intensity and phase of two perpendicular polarization states and applying a double-phase hologram technique, they enabled a single phase-only spatial light modulator to encode amplitude, phase and polarization together in the optical field.
Reading that information back is a problem for standard sensors, which only measure light intensity, or amplitude, and cannot directly detect phase or polarization. The researchers said they addressed that by combining tensor-polarization holography theory with a convolutional neural network to recover all three types of data from diffraction intensity images.
The neural network is trained using two complementary diffraction images, one captured with a vertical polarizer and one without. The researchers said the model learns to identify patterns linked to amplitude, phase and polarization by analysing those images. It then reconstructs all three at the same time, which they said improves storage density and boosts data transmission speed.
After confirming the concept, the team built a compact system capable of recording and reconstructing the encoded optical field within a polarization-sensitive material. During testing, intensity images were analysed to detect signatures related to amplitude, phase and polarization. Those signatures were then used as inputs for the neural network, enabling full 3D reconstruction using only intensity-based measurements.
“Overall, our results showed that multidimensional joint encoding substantially increased the information carried by a single holographic data page, thereby improving storage capacity,” said Tan. “In addition, neural network synchronous decoding reduced the need for complex measurements and step-by-step reconstruction, supporting more efficient readout and decoding. This could enable a practical route toward high-capacity, high-throughput holographic data storage.”
Tan said the method could have uses beyond storage if it is developed further.
“With further development and commercialization, this type of multidimensional holographic data storage could enable smaller data centers and more efficient large-scale archival storage, while also enhancing data processing and transmission efficiency,” said Tan. “It could also contribute to safer data transmission, optical encryption and advanced imaging.”
The researchers said the system remains at the research stage and needs more development before commercial use. Their next steps include increasing the gray levels used in encoding to expand capacity further and improving the long-term stability, uniformity and repeatability of the recording materials.
They also plan to combine the method with volumetric holographic multiplexing techniques, which could allow multiple pages and channels of data to be stored at once. The team said stronger integration between optical hardware and decoding algorithms will be needed for faster and more reliable data retrieval under real-world conditions.
