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OPTICAL DATA STORAGE|15 Article(s)
Four-level phase pair encoding and decoding with single interferometric phase retrieval for holographic data storage
Xiao Lin, Yong Huang, Yang Li, Jinyan Liu, Jinpeng Liu, Ruidan Kang, and Xiaodi Tan
We propose four-level phase pair encoding and decoding with single interferometric phase retrieval for holographic data storage. Inherent with phase pair encoding, phase shifting is generated by assigning a certain phase difference between two pixels of the phase pair. Multiple phase shifting operations are not required. In addition, a phase-readout reference beam can be a plane beam with an arbitrary phase in our method because phase shifting can be encoded on the phase-only spatial light modulator easily and accurately. Therefore, our method can not only increase the data transfer rate, but also improve the robustness of the holographic data storage system. Although the code rate of our method needs to be sacrificed by half, the code rate is still twice that of amplitude code when four-level phase encoding is used. We demonstrated experimentally that there is only a 1×10 2 order of bit error rate before error correcting, which is acceptable. We believe our method will further advance the phase-modulated holographic data storage technique. We propose four-level phase pair encoding and decoding with single interferometric phase retrieval for holographic data storage. Inherent with phase pair encoding, phase shifting is generated by assigning a certain phase difference between two pixels of the phase pair. Multiple phase shifting operations are not required. In addition, a phase-readout reference beam can be a plane beam with an arbitrary phase in our method because phase shifting can be encoded on the phase-only spatial light modulator easily and accurately. Therefore, our method can not only increase the data transfer rate, but also improve the robustness of the holographic data storage system. Although the code rate of our method needs to be sacrificed by half, the code rate is still twice that of amplitude code when four-level phase encoding is used. We demonstrated experimentally that there is only a 1×10 2 order of bit error rate before error correcting, which is acceptable. We believe our method will further advance the phase-modulated holographic data storage technique.
Chinese Optics Letters
- Publication Date: Mar. 10, 2018
- Vol. 16, Issue 3, 032101 (2018)
Spiral spectrum of Airy–Schell beams through non-Kolmogorov turbulence
Yun Zhu, Licheng Zhang, and Yixin Zhang
Based on the geometrical optics approximation, we analyze the effects of non-Kolmogorov turbulence on the spiral spectrum of the orbital angular momentum (OAM) of Airy–Schell beams. Our numerical results of Airy–Schell beams on the horizontal path show that the beam spreading due to diffraction is smaller for shorter wavelengths, a smaller OAM quantum number, a larger radius of the main ring, and a higher arbitrary transverse scale in weak turbulence. The oscillation frequency of the mode probability density of Airy–Schell beams in the radial direction is much lower than that of Hankel–Bessel beams. The mode probability densities of Airy–Schell and Hankel–Bessel beams are remarkably dependent on the wavelength and OAM quantum number. In order to improve the mode probability density, Airy–Schell beams with shorter wavelengths and lower OAM quantum numbers may be the better choice, which is diametrically opposite to Hankel–Bessel beams. Our research provides a reasonable basis for selecting light sources and precise tracking. Based on the geometrical optics approximation, we analyze the effects of non-Kolmogorov turbulence on the spiral spectrum of the orbital angular momentum (OAM) of Airy–Schell beams. Our numerical results of Airy–Schell beams on the horizontal path show that the beam spreading due to diffraction is smaller for shorter wavelengths, a smaller OAM quantum number, a larger radius of the main ring, and a higher arbitrary transverse scale in weak turbulence. The oscillation frequency of the mode probability density of Airy–Schell beams in the radial direction is much lower than that of Hankel–Bessel beams. The mode probability densities of Airy–Schell and Hankel–Bessel beams are remarkably dependent on the wavelength and OAM quantum number. In order to improve the mode probability density, Airy–Schell beams with shorter wavelengths and lower OAM quantum numbers may be the better choice, which is diametrically opposite to Hankel–Bessel beams. Our research provides a reasonable basis for selecting light sources and precise tracking.
Chinese Optics Letters
- Publication Date: Apr. 10, 2016
- Vol. 14, Issue 4, 042101 (2016)
Super-long longitudinal magnetization needle generated by focusing an azimuthally polarized and phase-modulated beam
Wangzi Ma, Dawei Zhang, Linwei Zhu, and Jiannong Chen
Based on the inverse Faraday effect, a super-long longitudinal magnetization needle can be induced by a transversely polarized needle-shaped electric field. This needle-shaped electric field can be obtained in the focal volume of the objective by focusing an azimuthally polarized vortex beam that is modulated both radially and azimuthally by a specifically designed annular phase filter. The numerical calculation shows that the full widths at half-maximums in longitudinal direction and in transverse direction of the magnetization needle are 28λ and 0.27λ. The corresponding needle aspect ratio of 103 is more than ten times larger than that of the magnetization needle fabricated by electron beam lithography. Based on the inverse Faraday effect, a super-long longitudinal magnetization needle can be induced by a transversely polarized needle-shaped electric field. This needle-shaped electric field can be obtained in the focal volume of the objective by focusing an azimuthally polarized vortex beam that is modulated both radially and azimuthally by a specifically designed annular phase filter. The numerical calculation shows that the full widths at half-maximums in longitudinal direction and in transverse direction of the magnetization needle are 28λ and 0.27λ. The corresponding needle aspect ratio of 103 is more than ten times larger than that of the magnetization needle fabricated by electron beam lithography.
Chinese Optics Letters
- Publication Date: May. 10, 2015
- Vol. 13, Issue 5, 052101 (2015)
Improved nonvolatile holographic storage sensitivity of near-stoichiometric LiNbO3:Fe:Mn crystals
Xiaochun Li, Dengxue Qu, Wenjie Wang, Xuejiao Zhao, Lingling Zhang, and Xuejuan Meng
We investigate the nonvolatile holographic storage characteristics of near-stoichiometric LiNbO3:Fe:Mn crystals with different Li2O contents. Experimental results indicate that the optimal value of Li2O content is about 49.6 mol%. Nonvolatile sensitivity S′ considerably improved to 0.15 cm/J because of the use of near-stoichiometric LiNbO3:Fe:Mn with 49.6 mol% Li2O. We investigate the nonvolatile holographic storage characteristics of near-stoichiometric LiNbO3:Fe:Mn crystals with different Li2O contents. Experimental results indicate that the optimal value of Li2O content is about 49.6 mol%. Nonvolatile sensitivity S′ considerably improved to 0.15 cm/J because of the use of near-stoichiometric LiNbO3:Fe:Mn with 49.6 mol% Li2O.
Chinese Optics Letters
- Publication Date: Nov. 30, 2012
- Vol. 10, Issue 12, 122101 (2012)
Laser direct writing pattern structures on AgInSbTe phase change thin film
Aihuan Dun, Jingsong Wei, and Fuxi Gan
Different pattern structures are obtained on the AgInSbTe (AIST) phase change film as induced by laser beam. Atomic force microscopy (AFM) was used to observe and analyze the different pattern structures. The AFM photos clearly show the gradually changing process of pattern structures induced by different threshold effects, such as crystallization threshold, microbump threshold, melting threshold, and ablation threshold. The analysis indicates that the AIST material is very effective in the fabrication of pattern structures and can offer relevant guidance for application of the material in the future. Different pattern structures are obtained on the AgInSbTe (AIST) phase change film as induced by laser beam. Atomic force microscopy (AFM) was used to observe and analyze the different pattern structures. The AFM photos clearly show the gradually changing process of pattern structures induced by different threshold effects, such as crystallization threshold, microbump threshold, melting threshold, and ablation threshold. The analysis indicates that the AIST material is very effective in the fabrication of pattern structures and can offer relevant guidance for application of the material in the future.
Chinese Optics Letters
- Publication Date: May. 31, 2011
- Vol. 9, Issue 8, 082101 (2011)
Three-dimensional multilevel memory based on laser-polarization-dependence birefringence
Guanghua Cheng, Qing Liu, Yishan Wang, Wei Zhao, and Guofu Chen
The femtosecond laser-modified region in isotropic glass medium shows a big optical birefringence. Transmission of the birefringent regions between two crossed polarizers depends on phase retardation and the orientation angle of the birefringent optical axes. Based on this effect, three-dimensional (3D) multilevel memory was proposed and demonstrated for nonvolatile memory up to eight levels, in contrast to the standard two-level technology. Eight-level writing and reading are distinguishable in fused silica with a near-infrared femtosecond laser. The retention of this memory is characterized for nonvolatile applications. The femtosecond laser-modified region in isotropic glass medium shows a big optical birefringence. Transmission of the birefringent regions between two crossed polarizers depends on phase retardation and the orientation angle of the birefringent optical axes. Based on this effect, three-dimensional (3D) multilevel memory was proposed and demonstrated for nonvolatile memory up to eight levels, in contrast to the standard two-level technology. Eight-level writing and reading are distinguishable in fused silica with a near-infrared femtosecond laser. The retention of this memory is characterized for nonvolatile applications.
Chinese Optics Letters
- Publication Date: Jan. 01, 2006
- Vol. 4, Issue 2, 02111 (2006)
Simulation of an apodizer's effect for high-density optical storage
Xiumin Gao, Wendong Xu, and Fuxi Gan
The effect of an apodizer with two parallel taper refractive surfaces is theoretically investigated for high-density optical storage. The apodizer may modulate an incident Gaussian beam into an annular beam. Simulation shows that with the increasing inner radius of the modulated beam, the focal spot shrinks obviously. The depolarization effect gets strong simultaneously, which induces the circular symmetry loss of the focal spot. In this process, pattern density of the orthogonal and longitudinal diffractive fields increases remarkably. The effect of an apodizer with two parallel taper refractive surfaces is theoretically investigated for high-density optical storage. The apodizer may modulate an incident Gaussian beam into an annular beam. Simulation shows that with the increasing inner radius of the modulated beam, the focal spot shrinks obviously. The depolarization effect gets strong simultaneously, which induces the circular symmetry loss of the focal spot. In this process, pattern density of the orthogonal and longitudinal diffractive fields increases remarkably.
Chinese Optics Letters
- Publication Date: Jan. 01, 2005
- Vol. 3, Issue 6, 06361 (2005)
Read-only memory disk with AgOx super-resolution mask layer
Feng Zhang, Yang Wang, Wendong Xu, Hongren Shi, and Fuxi Gan
A novel read-only memory (ROM) disk with an AgOx mask layer was proposed and studied in this letter. The AgOx films sputtered on the premastered substrates, with pits depth of 50 nm and pits length of 380 nm, were studied by an atomic force microscopy. The transmittances of these AgOx films were also measured by a spectrophotometer. Disk measurement was carried out by a dynamic setup with a laser wavelength of 632.8 nm and a lens numerical aperture (NA) of 0.40. The readout resolution limit of this setup was λ/(4NA) (400 nm). Results showed that the super-resolution readout happened only when the oxygen flow ratios were at suitable values for these disks. The best super-resolution performance was achieved at the oxygen flow ratio of 0.5 with the smoothest film surface. The super-resolution readout mechanism of these ROM disks was analyzed as well. A novel read-only memory (ROM) disk with an AgOx mask layer was proposed and studied in this letter. The AgOx films sputtered on the premastered substrates, with pits depth of 50 nm and pits length of 380 nm, were studied by an atomic force microscopy. The transmittances of these AgOx films were also measured by a spectrophotometer. Disk measurement was carried out by a dynamic setup with a laser wavelength of 632.8 nm and a lens numerical aperture (NA) of 0.40. The readout resolution limit of this setup was λ/(4NA) (400 nm). Results showed that the super-resolution readout happened only when the oxygen flow ratios were at suitable values for these disks. The best super-resolution performance was achieved at the oxygen flow ratio of 0.5 with the smoothest film surface. The super-resolution readout mechanism of these ROM disks was analyzed as well.
Chinese Optics Letters
- Publication Date: Jan. 01, 2005
- Vol. 3, Issue 2, 02113 (2005)
Three-dimensional optical data storage using a solid immersion lens to focus a femtosecond laser pulse
Fengtao He, Guanghua Cheng, Xiaoqiang Feng, Dongling Zhang, Zhao Cheng, Qing Liu, Wei Zhao, Guofu Chen, and Xun Hou
A solid immersion lens (SIL) has been applied to the writing and reading of three-dimensional optical data storage in transparent materials. Using a SIL with n=1.516 to focus a 150-fs, 800-nm Ti:sapphire laser, the 5-layer reading and writing of data are achieved in fused silica and polyethylene methacrylate at a density of 1.1*10^(12) b/cm3. Some advantages of the employment of SIL have been discussed. A solid immersion lens (SIL) has been applied to the writing and reading of three-dimensional optical data storage in transparent materials. Using a SIL with n=1.516 to focus a 150-fs, 800-nm Ti:sapphire laser, the 5-layer reading and writing of data are achieved in fused silica and polyethylene methacrylate at a density of 1.1*10^(12) b/cm3. Some advantages of the employment of SIL have been discussed.
Chinese Optics Letters
- Publication Date: Jan. 01, 2004
- Vol. 2, Issue 7, 07423 (2004)
Land/groove optical recording with GeTe/Sb2Te3 superlattice-like structure
Wei Qiang, Luping Shi, Towchong Chong, and Yang Cao
A superlattice-like (SLL) structure was applied to phase-change optical recording. The recording layer consisting of alternating thin layers of two different phase-change materials, GeTe and Sb2Te3, were grown by magnetron sputtering on polycarbonate substrates. Land/groove optical recording was adopted to suppress crosstalk and obtain a large track density. Dynamic properties of the SLL disc were investigated with the shortest 1T pulse duration of 8 ns. Clear eye pattern was observed after 10000 direct overwrite cycles. Erasability above 20 dB was achieved at a constant linear velocity of 19 m/s. Carrier-noise ratio (CNR) kept above 46 dB when the recording frequency reaches 21 MHz. The SLL phase change optical disc demonstrates a better recording performance than the Ge1Sb2Te4 and Ge1Sb4Te7 discs in terms of CNR, erasability, and overwrite jitter. A superlattice-like (SLL) structure was applied to phase-change optical recording. The recording layer consisting of alternating thin layers of two different phase-change materials, GeTe and Sb2Te3, were grown by magnetron sputtering on polycarbonate substrates. Land/groove optical recording was adopted to suppress crosstalk and obtain a large track density. Dynamic properties of the SLL disc were investigated with the shortest 1T pulse duration of 8 ns. Clear eye pattern was observed after 10000 direct overwrite cycles. Erasability above 20 dB was achieved at a constant linear velocity of 19 m/s. Carrier-noise ratio (CNR) kept above 46 dB when the recording frequency reaches 21 MHz. The SLL phase change optical disc demonstrates a better recording performance than the Ge1Sb2Te4 and Ge1Sb4Te7 discs in terms of CNR, erasability, and overwrite jitter.
Chinese Optics Letters
- Publication Date: Jan. 01, 2004
- Vol. 2, Issue 6, 06356 (2004)
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