Our report details a novel approach using polarization holography for the precise detection of vector vortex beams' (VVBs) polarization distribution. We will discuss multiple methodologies facilitated by this technique, offering insights into VVBs' characterization. Upon successful detection, we extract the VVBs' polarization states, allowing for their accurate placement on the Poincaré sphere. The obtained results affirm polarization holography's potential as an effective alternative to conventional measurement methods. This advancement propels polarization holography towards widespread adoption in optical component processing.
Polarization holography is a newly researched field, that has gained traction with the development of tensor theory. It primarily focuses on the interaction between polarization waves and photosensitive materials. The extraordinary capabilities in modulating the amplitude, phase, and polarization of light have resulted in several new applications, such as holographic data storage technology, polarization multiplexing, vector or vortex beams, and optical functional devices. In this paper, fundamental research on polarization holography with linear polarized light, a component of the theory of polarization holography, has been reviewed. Primarily, the effect of various polarization changes on the linear and nonlinear polarization characteristics of reconstructed light wave under continuous exposure and during holographic recording and reconstruction have been focused upon. The polarization modulation realized using these polarization characteristics exhibits unusual functionalities, rendering polarization holography as an attractive research topic in many fields of applications.
Although polarization holography introduces polarization dimensions, it is well known that polarization has only two orthogonal dimensions, and the expansion of recording capabilities is limited. Therefore, we introduce the polarization encoding for theoretical analysis and calculation, the orthogonal polarization array of arbitrary dimensions is obtained. Assuming that the n-dimensional vectors Q1, Q2, …, and Qx are a group of non-zero vectors that are orthogonal to each other in the orthogonal polarization array. The Schmidt orthogonalization method is used to expand the column vector group of the n-dimensional orthogonal polarization array into a set of canonical orthogonal basis of the space Kn. During the experiment, when the signal S1 is recorded with Q1, it can be faithfully reconstructed with Q1, while it shows null reconstruction with Q2 or Qx. By analogy, multiple recording and independent reconstruction experiments are carried out successively.
The old theory of polarization holography is based on Jones matrix formalism, where the angle between two lights to be interfered each other should be small, and the results are limited under the paraxial approximation. However, since the tensor theory of polarization holography was proposed, the research of polarized holography has become hot, and has made a lot of new progress. There are also many researching works of reconstruction characteristics have been reported. One of the examples is that multi-channel recording was applied to data storage high density recording. In this paper, the representative works are introduced.
KEYWORDS: Data storage, Image segmentation, Holography, Deep learning, Holographic data storage systems, Neural networks, Education and training, Data modeling, Mathematical optimization, Holograms
Experiments have shown that deep learning can improve the data reading of holographic data storage. However, it requires a large amount of storage materials and time to obtain data to optimize the network model. In data encoding, each encoded data page consists of 51sub-pages with the same structure. This paper proposes a deep learning method for image segmentation based on encoding features in collinear holographic data storage. Using a deep learning method of image segmentation, the encoded data page is segmented into data sub-pages. It can reduce material loss and data collection time.
Linear polarization holography based on tensor theory has yielded numerous intriguing discoveries and applications. Utilizing theories such as null reconstruction, applications beneficial for holographic optical storage have been realized, with dual-channel polarization multiplexing being one of them. However, previous research has found deviations in the grayscale ratios on reconstructed images compared to original images, especially when uploading grayscale images with higher levels, such as 4-level grayscale images. This study conduct experiments using different recording methods to identify the source of grayscale crosstalk from a single test image. The results indicate that the recording modes, whether co-polarized or orthogonal polarized, do not significantly disrupt amplitude recording.
Vector vortex beams (VVBs) have attracted world’s attention due to its promise of unprecedented capabilities for applications. It is important that develop an easy and feasible method to character the spatially inhomogeneous distribution of polarization of VVB. In this paper, we propose a method for measuring the polarization distribution of arbitrary vector vortex beams using polarization holography. The experimental results show that the results measured by polarization holography for VVBs are basically similar to those measured by the conventional method. We believe that polarization holography is expected to become a popular optical component processing technology in future.
There are many ways to realize null reconstruction in polarization holography, which can be divided into two types. One is the null reconstruction without exposure response coefficient constraint, and the other is the null reconstruction limited by the exposure response coefficient. On the basis of previous studies, we have further studied these two types of null reconstruction, and obtained the necessary conditions for realizing the two types of null reconstruction under arbitrary interference angle and polarization state.
KEYWORDS: Data modeling, Signal to noise ratio, Deep learning, Holographic data storage systems, Holography, Data storage, Education and training, Objectives, Neural networks, Reliability
In recent years, optical holographic data storage system has gradually become a research hotspot and a strong competitor of big data storage due to its high data transfer rate, long storage life and high storage density. In the collinear amplitude modulated holographic data storage system, in order to improve the storage density, a high magnification objective lens is usually used as the recording lens to record the encoded data pages in the holographic storage medium. Therefore, when the objective lens is focused on the holographic storage medium, the accuracy and reliability of data recording and reading can be guaranteed. However, in the process of normal use of the system, environmental interference and other factors will inevitably lead to defocusing of the objective lens, which will result in high bit-error-rate (BER) and low signal-to-noise ratio (SNR) of the recorded and read coding information, affecting the accuracy and reliability of information reading. In this paper, we propose a collinear amplitude modulated holographic data storage system objective defocusing correction model using deep learning. Only a training model with defocusing distance of 100μm can be used to correct the defocusing of the objective lens with defocusing distance less than 100μm. The reconstructed BER is reduced to less than 1/10 of the original data, and the SNR is increased to more than 5 times of the original data. The reliability and accuracy of system record reading are improved.
Polarization holography can record and reconstruct information by means of polarization state modulation. It can record the amplitude, phase and polarization information of light field by recording the polarization grating of two coherent waves with different polarization states. This technology has been used to record two or four pairs of 2-level grayscale images in the case of two or four channels in the past. Now we designed experiments to record and reconstruct two different 4-level grayscale images at the same point of polarization-sensitive media through the faithful reconstruction of linearly polarization holography by matching the exposure time and the polarization angles of the two interference waves. We verify that it is possible to reconstruct two 4-level intensity images at the same point to achieve polarization and intensity multiplexing.
In Big Data era, holographic data storage has become a good candidate recording technology, because of there are not only large storage capacities, but also high transfer rates. However, the realized capacity of it has a big gap to the theory. Polarization holography, a newly researched field, with the extraordinary capabilities in modulating the amplitude, phase, and polarization of light have resulted in several new applications, such as holographic storage technology, multichannel polarization multiplexing, vector beams, and optical functional devices. In this paper, the fundamental research on polarization holography with linear polarized light, a component of the theory of polarization holography, has been introduced. The polarization modulation realized using these polarization characteristics exhibits unusual functionalities, rendering polarization holography as an attractive research topic in a novel method for increasing the capacity of holographic data storage has been provided.
Polarization holography has gained traction with the development of tensor theory. It primarily focuses on the interaction between polarization waves and photosensitive materials. By introducing the polarization characteristics of light into conventional holography, more degrees of freedom can be provided to control optical information. Based on the polarization modulation of polarization hologram, we propose a method to realize bifocal-polarization holographic lens in volume hologram. Two foci can be generated simultaneously or separately by changing the polarization state of the reading wave. The material used is a PQ/PMMA polarization sensitive medium, the thickness is 1.5mm. The bifocal-polarization holographic lens has 112 mm clear aperture and 446mm focal length.
KEYWORDS: Holography, Polarization, Dielectric polarization, Multiplexing, Camera shutters, Diffraction, Photonics, Dielectrics, Wavelength division multiplexing, Signal to noise ratio
The null reconstruction can be used to realize multi-channel recording, thereby improves the storage capacity. In this work, phenanthrenequinone-doped poly(methyl methacrylate) photopolymer (PQ/PMMA) that is sensitive to the polarized wave, is used as the recording medium. To better reach the null reconstruction, we need to control exposure time and intensity in the recording stage. By adopting the suitable experimental parameters, the crosstalk between the two holograms is negligible. The analysis of the experimental results shows that the ratio of optical powers of the signal wave to that of reference wave is 1:8-1:10, the exposure time is about 12 minutes, and the optimal signal-to-noise ratio can reach 21:1.
In this letter, we employ vector wave polarization holography theory based on the dielectric tensor description. Newly developed vector wave polarized holography theory breaks up the limitation of paraxial approximation in polarization holograms. Various interesting phenomena have been investigated, the faithful reconstruction is of particular significance. The faithful reconstruction (FR) effect indicates that the polarization state of the reconstruction wave is identical to that of the signal wave, it can be achieved process when the intensity and polarization holographic grating attained a balance during after exposure. The FR property related to the linearly, circularly and elliptically polarization is investigated in our previous work. In our experiment, the recording medium we use is the bulk polarization holographic recording material of phenanthrenequinone-doped polymethyl methacrylate photopolymer (PQ-PMMA). The mixed mass ratio of methyl methacrylate (MMA), azobisisobutyronitrile (AIBN) and phenanthrenequinone (PQ) are 100:1:1. Under the cross-angle of π/2 inside the recording media, the polarized holographic reconstruction of the circular polarization recorded by a horizontal linear polarization wave is calculated. It is found that the circularly polarized signal can be faithful reconstruction by arbitrarily polarized reading waves. However, when the polarization of the reading wave is orthogonal to the polarization of the reference wave, it will occur the null reconstruction (NR). The FR technology will provide a simpler and more effective method for a circular polarization generator. At the same time, the NR technology can quickly detect that the polarized wave is vertical polarization.
Phase-modulated holographic data storage shows a great prospect in Ultra-high-definition (UHD) information display and data storage due to its higher capacity than amplitude modulation. However, the phase reconstruction is more sensitive to noise in the spectrum plane. In this paper, we proposed to use the low-depth camera to obtain the spectral intensity of the reconstructed beam, and used iterative Fourier transform algorithm to retrieve phase. Simulation and experiment show that this method has stronger noise suppression performance.
Based on tensor polarization holography, the variation of exposure response coefficient with the increase of exposure energy under different recording process is introduced in this paper. We find that different recording processes have different effects on the exposure response coefficient. However, at the beginning of exposure, there is an initial value of the exposure response coefficient independent of the holographic recording process. With this special phenomenon, polarization modulation of reconstructed wave can be easily realized at low exposure energy, such as faithful reconstruction, orthogonal reconstruction and null reconstruction.
Polarization holography has great potential in Ultra-high-definition (UHD) information diplay and data storage. Due to the faithful reconstruction in polarization holography, the storage capacity is further improved easily. In this paper, a device for generating vector vortex beam is demonstrated using the faithful reconstruction characteristics. Through the analysis of the experimental results, it is found that the helical phase order corresponding to different polarization states is different in the transmission process. It shows the independence of vector vortex beam propagation. This method has a certain research space in optical storage, and application prospect in optical micromanipulation optical tweezers.
We used the amplitude coding method of 3:16, that is, in a 4 * 4 pixel matrix, only three pixels are in the on state, and the remaining pixels are in the off state. In the collinear amplitude holographic data storage system, U-Net full convolution neural network is used to denoise the amplitude coded image obtained by the detector. The experimental results show that the bit error rate can be reduced to less than 1% from 10% and the image signal-to-noise ratio can be increased by more than 5 times.
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