7D High-Dynamic Spin-Multiplexing

Abstract

Multiplexing technology creates several orthogonal data channels and dimensions for high-density information encoding and is irreplaceable in large-capacity information storage, and communication, etc. The multiplexing dimensions are constructed by light attributes and spatial dimensions. However, limited by the degree of freedom of interaction between light and material structure parameters, the multiplexing dimension exploitation method is still confused. Herein, a 7D Spin-multiplexing technique is proposed. Spin structures with four independent attributes (color center type, spin axis, spatial distribution, and dipole direction) are constructed as coding basic units. Based on the four independent spin physical effects, the corresponding photoluminescence wavelength, magnetic field, microwave, and polarization are created into four orthogonal multiplexing dimensions. Combined with the 3D of space, a 7D multiplexing method is established, which possesses the highest dimension number compared with 6 dimensions in the previous study. The basic spin unit is prepared by a self-developed laser-induced manufacturing process. The free state information of spin is read out by four physical quantities. Based on the multiple dimensions, the information is highly dynamically multiplexed to enhance information storage efficiency. Moreover, the high-dynamic in situ image encryption/marking is demonstrated. It implies a new paradigm for ultra-high-capacity storage and real-time encryption.

Keywords: data storage; encryption; laser direct writing; multiplexing; silicon carbide color centers.

Figure 1

Overview of conventional multiplexing and 7D Spin‐multiplexing. a) Conventional multiplexing. b) Our proposed 7D Spin‐multiplexing. Among them, the blue polygons represent the SiC crystals. The balls and arrows represent the electrons and spin properties of spin structures, respectively. The direction of arrow, color of ball, vertical position, and direction of surrounding balls represent the axial direction (AD), color center type (CC), height (H), and dipole direction (DD) of spin structures, respectively. |1>_AD1, |1>_AD2 and |0> are three energy levels of spin structures. Yellow circular light indicates the code of corresponding spin structure is 1 (the electron transitions to the spin level |1>), and the rest of the spin structures are coded 0. c–f) magnetic field (c), wavelength (d), microwave (e) and polarization dimension (f) of 7D Spin‐multiplexing. The upper, middle, and lower parts of each graph are respectively the spin structures of different properties, the spectrum of the spin structure, and the concrete representation of the spin properties (dashboard). g) Externally controlled physical quantities, whole structure, and PL image with each dimension of 7D Spin‐multiplexing.

Figure 2

Fabrication and product characterization Spin‐multiplexing. a) Preparation of SiC precursors (PCS and PCS‐C) from PDMS‐PVC by using a flat‐top laser (SPR1). b) SiC preparation from SiC precursors by focused Gaussian laser (SPR2). c) SiC spin structures fabrication by femtosecond laser. d) PDMS protective layer fabrication and PL acquisition. The insets in a and b are the energy (E) distribution of the laser beam on the X‐axis (purple dash line). The inset in c is the energy (E) related to the pulse duration of the fs laser (purple dash line). The main two kinds of SiC spin structures that fabricated by femtosecond laser. e) Optical microscopic image (OMI) and PL image (PLI) of SMED_4 × 4. f) TEM image (left part) and properties analysis (right part) of SiC nanocrystals on the cross‐section (scale bar, 500 nm). Black regions are SiC nanocrystals. The axial direction is perpendicular to the direction of crystal growth, and the axial direction of the twin crystal is marked by the vector sum of the axial direction of each single crystal. The dipole direction is calibrated by the direction of the crystal in the plane that is perpendicular to the axial direction. g) Continuous‐wave ODMR spectrum of PL5 and PL6 in 4H‐SiC. PL5 and PL6 peaks are at 1.352 and 1.362 GHz, respectively. The inset shows the TEM image of divacancy (V_SiV_C), and the high‐resolution TEM images of color centers are shown in Figure S5f,g (Supporting Information). h) Rabi oscillation of PL5 in Spin‐multiplexing.

Figure 3

Encoding mechanism and corresponding code images of Spin‐multiplexing. a–d) Spectra used for encoding of magnetic field dimension (a), wavelength dimension (b), microwave dimension (c), and polarization dimension (d). The spectra show different peak positions due to the different spin properties of each point. The 16 points are labeled as Point 1 to Point 16 from left to right and from top to bottom. e) Code images of the Z = 0 µm plane. A total of 24 multiplexing images are encoded in three magnetic field channels (M ₁‐M ₃), two wavelength channels (λ ₁, λ ₂), two microwave channels (t ₁, t ₂), and two polarization channels (θ ₁, θ ₂). Encoding units with bright points possess spin structures with the corresponding properties required for each multiplexing channel, while dark spots do not. Therefore, bright points represent the code 1, and dark points represent the code 0. f) Schematic diagram of multiplexing in Z direction. Above and below cubes represent the Spin‐multiplexing structures in Z = 5 µm and Z = 0 µm planes, respectively. g) Code images of the Z = 5 µm plane.

Figure 4

Real‐time and highly dynamic encryption/watermarking system based on SMED. a) The schematic diagram of system composition and system application scheme. The inset at the bottom right shows the encryption/watermarking system and encrypted/watermarked objects (secret document). The system consists of a laser, two polarization rotators (PR), a control chip, a lens, and a camera with SMED. b) Imaging results of secret document encryption. The images in the first row are whole encrypted images, and the images in the second row are enlarged images of the SMED region. White lines in second‐row images are additional lines added to aid reading.