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.
In the tensor polarization holography theory, parameters A and B represent the scalar and tensor coefficients of the photo-induced change in the dielectric tensor, respectively. A/B is called the exposure response coefficient, a key factor for manipulating the polarization state of the reconstructed wave in polarization holography. We measure the initial exposure response coefficient of the polarization-sensitive material, phenanthrenequinone-doped polymethyl methacrylate (PQ/PMMA), and analyze the effect of the interference angle and the polarization states of the signal and reference waves on the coefficient in linear polarization holography. To better understand the linear polarization holography, we develop a formula to describe the law of the initial exposure response coefficient.
Polarization grating (PG) divides the incident wave into the left- and right-handed circularly polarized waves, the intensities of two waves depending on the state of polarization of incident wave. Large deflection angle of the commercial PG is usually made by the grating cascade due to the limit of grating period. While using the tensor polarization holography theory, arbitrary deflection angles of PGs have been designed, where the polarization-sensitive material phenanthraquinone-doped polymethyl methacrylate (PQ/PMMA) is utilized as the recording medium in our experiments. We have made PG with the deflection angle of 40°.
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.
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 based on tensor theory can accurately describe the reconstruction characteristics at arbitrary interference angles, so some optical elements such as wave plates can be produced by polarization holography. The wave plates are important optical elements that can control the phase and polarization state of wave. Conventional wave plates convert the polarization state of the incident wave through crystal birefringence and then require the accurate thickness. Based on the polarization holography described by tensor theory, we produce the half-wave plate whose azimuthal angle of fast axis may be arbitrary by using the polarization sensitive material, phenanthrenequinone-doped poly methyl methacrylate (PQ/PMMA).
The tensor polarization holography theory has predicated some phenomena and been verified by the experiments. In the theory, the parameters α and β represent the scalar and tensor coefficients of the photoinduced change in dielectric tensor respectively. The ratio of α to β, called the exposure response coefficient, is a key to manipulate the polarization state of reconstructed waves and deepen the understanding of tensor polarization holography theory. In this work, for the polarization-sensitive material, phenanthrenequinone-doped poly methyl methacrylate (PQ/PMMA), we analyze the effect of interference angle and the polarization states of signal wave on the initial exposure response coefficient when the reference wave is s-polarized in linear polarization holography.
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.
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.
Based on polarization holography theory, the plane bifocal vector lens is studied. In previous studies, the bifocal vector lens were limited to cross-angle π/2 and bulk materials. However, when the two waves are orthogonal circularly polarized state, the plane bifocal vector lens can be realized, and the limitation of cross-angle π/2 and bulk materials can be broken. The lens produces corresponding focus output through the reading wave with different polarization states, which can be used for large-area optical element research.
Collinear holography data storage (CHDS) is a promising solution for “cold data” storage in the big data age. Studies adopt “amplitude type” and “phase type” orthogonal reference have been sequentially reported for the performance improvement of CHDS. Data from different users can be storage and readout separately by different orthogonal reference, which is meaningful for the application of security data storage. In this paper, a newly “phase type” orthogonal reference specified by a Hadamard orthogonal matrix is proposed for identity information storage. Each one Hadamard vector on behalf of a “phase type” reference, and the symbols “1” and “-1” in Hadamard matrix stands for the phase of 0 and pi of the reference pixel. Several different data pages are recorded using different orthogonal reference in advance, and there is only the specific data page which is matched to the orthogonal reference can be reproduced in the process of reconstruction. The action mechanism of orthogonal reference is analyzed, and the feasibility of the system is verified by numerical simulations and primary experiments.
In polarization holography, the polarization information is recorded in the photopolymer material by interference, and the polarization state of the reconstructed wave can be calculated accurately by tensor method. Based on the guidance of tensor theory, this paper systematically analyzes the method of faithful reconstruction under any interference angle independent of exposure energy, and gives experimental verification under the condition of 40° interference angle. This conclusion is helpful to broaden our understanding of polarization holography based on tensor theory, and can be applied to the research of polarization multiplexing multi-channel holography.
The concentration of photosen-sitizer is an important factor affecting the properties of holographic materials. Most researchers use doping or copolymerization methods to increase the saturation dissolvability of photo-sensitizer. However, the addition of multiple components will reduce the molecular mass of the photoproducts and the polymer substrate, resulting in poor stability of the grating. In this paper, we studied the solubility of phenanthraquinone (PQ) in MMA at different temperatures. At 60 °C, the solubility of PQ could reach 1.8%. Meanwhile, we found that the thermo-initiator concentration of 2,2-Azobis(AIBN) affected long-chain carbon polymerization. Therefore, proper concentration balance has a huge impact on the performance of the materials. Finally, we obtained a relatively suitable concentration balance of PQ/PMMA photopolymer, making it more suitable for volume holographic data storage.
Faithful reconstruction, which is a key phenomenon in optical data storage, is significant in polarization holography and has attracted much attention. It is defined as the reconstructed wave being identical to the signal wave. We design an experiment to observe the faithful reconstruction of elliptical polarization holography in which the two orthogonal elliptical polarization waves are applied in the recording stage. In the experiment, phenanthrenequinone-doped poly methyl methacrylate is used as the recording material, and the angle between the signal and reference waves is ∼56 deg. We control the exposure time of recording material to observe the faithful reconstruction of orthogonal elliptical polarization holography. How to obtain the faithful reconstruction is interesting work; therefore, we propose a prerequisite for faithful reconstruction. Although the prerequisite is derived from orthogonal elliptical polarization holography, it could also be applied in orthogonal linear and circular polarization holography. The result may be helpful for understanding the faithful reconstruction of orthogonal polarization holography.
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