Jinliang Zang

Null reconstruction of orthogonal circular polarization hologram with large recording angle

We report on the null reconstruction of polarization volume hologram recorded by orthogonal circularly polarized waves with a large cross angle. Based on the recently developed tensor theory for polarization holography, the disappearance of the reconstruction was analytically verified, where a nice agreement was found between the experimental and theoretical results. When the polarization and intensity hologram attain a balance, not only the null reconstruction but also the faithful reconstruction can be realized by the illumination of the orthogonal reference wave and original reference wave. As a consequence of the hologram recorded without paraxial approximation, the null reconstruction may lead to important applications, such as a potential enhancement in optical storage capacity for volume holograms.

Investigation of the extraordinary null reconstruction phenomenon in polarization volume hologram

Polarization holography is the superposition of differently polarized beams. Due to its ability to record the polarization states, some extraordinary optical phenomena were found in the polarization holography. For example, the recently reported null-reconstruction phenomenon in polarization volume hologram is odd for the conventional holography which only records the amplitude and phase. In this paper, we perform a thorough investigation of the null reconstruction of polarization hologram recorded by orthogonal circularly polarized waves. To explore the mechanism behind this phenomenon, an interferometry was built to measure the phase difference between the same polarized components within the reconstructed wave. The phase difference of π was secured in our experiment, indicating a destructive interfering effect, which nicely explains the extraordinary null reconstruction observed in the polarization hologram.

Dual-channel recording based on the null reconstruction effect of orthogonal linear polarization holography

We report on dual-channel recording within polarization holography written by orthogonal linear polarization waves. The null reconstruction effect (NRE) of linear polarization holography was experimentally achieved at a large cross-angle of π/2 inside the polarization-sensitive media. Based on the NRE, two polarization encoded holograms were recorded in a dual-channel recording system with negligible inter-channel crosstalk. The two polarization multiplexed holograms could then be sequentially or simultaneously readout by shifting the polarization state of reference wave with the best signal-to-noise of 18:1 obtained within the experiment.

Modes Manipulation Within Subwavelength Metallic Gratings

Surface plasmon polariton (SPP) and cavity modes supported by the plasmonic gratings are often of hybrid nature in ruling light-nanostructure interactions. The coupling of incident light to SPP waves through the excitation of SPP modes usually traps the light at the air-metal interface, while the coupling to standing waves through cavity modes confines the light within the cavities. However, in a specific application, the highly selective coupling of incident light to either SPP or cavity mode is always required. We present here, for a single metal-insulator-metal (MIM) groove, the coupling strength of incident light to a certain mode can be engineered by varying the groove width and depth. To further enhance the coupling selectivity, the periodicity was introduced to the MIM grooves: When the period approaches (deviates from) the wavelength of SPPs, the incident light highly couples to SPP (cavity) mode, due to the constructive (destructive) interference between the propagating SPPs at metal-air interfaces. Two types of metallic gratings, aluminum grating with its period approaching the λSPP and iridium grating with its period far away deviating from the λSPP, were fabricated and measured. The almost null TM transmission through aluminum grating and detection of surface enhanced Raman scattering (SERS) signal from iridium grating solidly guarantee the validity of the proposed method in manipulating the modes, through which the energy flow can be guided to its supposed-to-appear regions.

Volume holographic recording in Irgacure 784-doped PMMA photopolymer

Photoinitiator plays a crucial role on photopolymer. Unlike photoinitiator phenanthrenequinone (PQ), the solubility of Irgacure 784 dissolved in MMA is very high. In this paper, we use Irgacure 784 as photoinitiator doped in poly(methyl methacrylate)(PMMA)to make a bulk photopolymer with high photoinitiator concentration for holographic data storage. The effect of concentration of photoinitiator and record intensity are experimentally investigated. The results reveal the material has an optimum condition in holographic recording. A comparison between our material and the material of PQ doped PMMA is carried out by experiment. It is found that our material has better performance on diffraction efficiency, refractive index modulation and recording sensitivity. Besides, this material also has polarization sensitivity, which can be applied to polarization holography. With the capacity of recording polarization holography and conventional intensity holography simultaneously, the Irgacure 784 doped PMMA material is expected to be applied in holographic data storage.

Inverse polarizing effect of an elliptical-polarization recorded hologram at a large cross angle.

We report on the inverse polarizing effect (IPE) of an elliptical-polarization recorded hologram at a large recording angle. The IPE is a polarizing phenomenon in which the reconstructed signal switches the major and minor axes and keeps the original polarization, direction compared, to that of the signal wave. In reviewing the case of a linear-polarization and circular-polarization recorded hologram, we found that the IPE is a unique phenomenon for elliptical polarization. The IPE was observed at the cross angle of 38° experimentally, and was theoretically explained using tensor theory to remove paraxial limitation.

Polarization-controlled dual images recording with linear polarization holography (Conference Presentation)

Polarization-Controlled dual images recording with linear polarization holography Jinliang Zang*, Fenglan Fan, Ying Liu, Yifan Hong, Long Shao, Xiaodi Tan （School of Optoelectronics, Beijing Institute of Technology, 5 South Zhongguancun Street, Haidian District, Beijing 100081, China 100081） *Corresponding author: jlzang@bit.edu.cn Abstract: Polarization holography is a promising technique for its unique capacity of recording intensity, phase as well as polarization of light wave field simultaneously. In recent years, dual-channel images recording by polarization holography has been proposed. However, in conventional dual-channel images recording, an unchanged polarized reference wave is employed while signal waves have orthogonal polarization, which makes two holographic images can only be read out simultaneously. In this paper, we report polarization-controlled dual images recording within polarization holography written by orthogonal linear polarization waves. In this method, two polarization multiplexed holographic images could be sequentially readout by shifting the polarization state of reference wave based on null reconstruction effect(NRE) of linear polarization holography. NRE is an unique phenomena in polarization holography which means the diffraction efficiency goes down to zero when the hologram is reconstructed by orthogonal polarized reading wave. In this paper, we study polarization holography recorded by orthogonal linear waves and find that the NRE of orthogonal linear polarization holography can be achieved at large cross-angle of inside the polarization-sensitive media. The NRE of linear polarization holography is experimentally demonstrated by recording orthogonal linear polarization hologram in fabricated cubic material PQ/PMMA whose size is 10 mm ×10 mm ×15 mm. Based on the NRE of orthogonal linear polarization holography, polarization-controlled dual images recording is carried out. Two images encoded by orthogonal linear polarization waves are sequentially recorded in same position of cubic PQ/PMMA by orthogonal linear polarization holography. In reconstruction stage, The two holographic images are sequentially readout by shifting the polarization state of reference wave with negligible inter-channel crosstalk. The experimental results agree well with theoretical predictions. And this polarization-controlled dual images recording method has promising applications in optical storage, vector light field modulation and multi-functional optical devices. Keywords: Polarization holography, Holographic data storage, Polarization-multiplex, Image processing

Volume holographic recording in bis(2,6-difluoro-3-(1-hydropyrrol-1-yl)phenyl)titanocene-doped PMMA photopolymer (Conference Presentation)

Holographic data storage has large storage capacity and high transfer rate, it becomes one of the next-generation information storage technologies. Bis(2,6-difluoro-3-(1-hydropyrrol-1-yl)phenyl)titanocene (IRG 784) is a good photoinitiator doped in photopolymer, poly(methyl methacrylate) （PMMA）is an excellent choice to making photopolymer with thickness of millimeter range. The solubility of phenanthrenequinone in MMA is a little low, for IRG 784 is very high. In this paper, I use IRG 784 as photoinitiator doped in PMMA made a kind of photopolymer with thickness of millimeter range for holographic data storage. We studied the optical characteristics of IRG 784–doped PMMA photopolymer with different weight ratio of IRG 784 doped. For the preparation of material, we use methyl methacrylate solution as the monomer, azo-bis-isobutyronitrile as the thermo-initiator. The samples with clear optical transmission is orangered. The wavelength of laser for recording and reconstructing we used was 532nm. In the recording process, recording waves interfered for 2 seconds with the cross angle of 60 degrees. After 2 seconds is the reconstruction process, the original reference wave reconstructed the grating for 0.6 seconds. These two processes cycled until the reaction ended. We set the polarization state of signal wave as s-polarization. Both s-polarization and p-polarization as reference wave we used to recording. Through a series of experiments, we can conclude that the weight ratio of IRG 784 dissolved in MMA is significant to increase diffraction efficiency. Although the diffraction efficiency is lower than in traditional holography, our material can be used in polarization holography.

Research of circular polarized holography with a large crossing angle under a common condition (Conference Presentation)

Polarization holography is the coherent interference of the beams that can have the different polarized states. The early-stage theory of polarization holography is based on Jones matrix, where the paraxial approximation is assumed, while the theory of polarization holography represented by dielectric tensor can describe the case with a large crossing angle. And it also depicts the relationship between diffraction light and interference light. During the research people find some extraordinary phenomenon, such as null reconstruction and inverse polarizing effect. But there is a disadvantage in this new polarization holography theory, where only under a peculiar circumstance can we get a faithful reconstruction. The circumstance can be expressed as “A+B=0”, where A and B refer to the coefficients for intensity and polarization holograms respectively. In this research, we calculate the formula of diffraction light’s polarization, and extract the A+B factor in it. Then we establish a series of equations which can let the diffraction light faithfully reconstruct, no matter what value of A plus B is. From the result, we can use an artificial reference beam which is corresponding to the signal beam to generate the hologram. Under this condition, the polarization of the diffraction light is similar to the signal. For simplification, we only discuss the signal wave with circular polarization and experimentally verify the result.

Investigation of faithful reconstruction in nonparaxial approximation polarization holography

Faithful reconstruction, the polarization state of the diffraction wave being identical to that of the signal wave, is the primary target in polarization holography. With the large crossing angle between signal and reference wave, namely, nonparaxial approximation, attaining a balance between intensity and polarization grating is generally known as a prerequisite for faithful reconstruction. However, obtaining such a balance point within polarization-sensitive material has long been known as a challenging job, due to its extremely strict exposure condition. In this paper, we report on a smart method with the well-designed reference and reading wave to faithfully reconstruct the signal wave at an arbitrary exposure energy. Moreover, when the signal is circularly polarized, the diffraction efficiency can be precisely manipulated by changing the reading wave’s polarization state, which is favorable for optical storage and functional diffractive optical elements.