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OPTICAL DATA STORAGE|18 Article(s)
Comparison of Two Different Mechanisms in Dual-Beam Super-Resolution Optical Recording
Qiao Hu, Xinjun Guo, Xupeng Yuan, Zongsong Gan, and Hao Ruan
Two mechanisms of realizing dual-beam super-resolution optical recording are compared in this paper. One is super-resolution photoinduction-inhibited nanolithography (SPIN), and the other is stimulated emission depletion (STED). We establish a dynamic physical model of STED-based dual-beam super-resolution optical recording technology and study its mechanism in the photo-polymerization process. The differences in dot size and resolution between SPIN-based and STED-based dual-beam super-resolution optical recording technologies are simulated. The results show that the STED-based dual-beam super-resolution optical recording technology has the advantages of no inhibitor and simple principle, however, it needs higher dual-beam intensity and has lower inhibition efficiency of polymerization. In addition, the recording uniformity becomes more unsatisfactory and the dot size increases in the multi-point recording scenario. On the contrary, the SPIN-based dual-beam super-resolution optical recording technology requires much lower dual-beam intensity, and the initiator molecule consumption will cancel out the effect of the inhibitor molecule consumption, leading to great uniformity and stability under multi-point recording. Therefore, the SPIN-based dual-beam super-resolution optical recording technology has better prospect in the field of ultra-high density optical data storage. Two mechanisms of realizing dual-beam super-resolution optical recording are compared in this paper. One is super-resolution photoinduction-inhibited nanolithography (SPIN), and the other is stimulated emission depletion (STED). We establish a dynamic physical model of STED-based dual-beam super-resolution optical recording technology and study its mechanism in the photo-polymerization process. The differences in dot size and resolution between SPIN-based and STED-based dual-beam super-resolution optical recording technologies are simulated. The results show that the STED-based dual-beam super-resolution optical recording technology has the advantages of no inhibitor and simple principle, however, it needs higher dual-beam intensity and has lower inhibition efficiency of polymerization. In addition, the recording uniformity becomes more unsatisfactory and the dot size increases in the multi-point recording scenario. On the contrary, the SPIN-based dual-beam super-resolution optical recording technology requires much lower dual-beam intensity, and the initiator molecule consumption will cancel out the effect of the inhibitor molecule consumption, leading to great uniformity and stability under multi-point recording. Therefore, the SPIN-based dual-beam super-resolution optical recording technology has better prospect in the field of ultra-high density optical data storage.
Acta Optica Sinica
- Publication Date: Jul. 11, 2019
- Vol. 39, Issue 7, 0721001 (2019)
Traditional and Differential Readout Technology for Super-Resolution Near-Field Structure Disc
Hu Wenhua, Chang Shengli, Yang Jiankun, Li Xiujian, and Tan Jichun
Based on the established simple model of an optical system, the traditional readout signal of super-resolution near-field structure (Super-RENS) disc is simulated according to scalar diffraction theory and angular spectrum method. By comparing simulation results with experimental signals, the validity of the calculation method is proved. Moreover, the differential signal, which is the difference of signals read out by high and low power incident laser, is simulated for single track and three tracks recording pattern. It is shown that, by using the differential readout method, the cross talk from adjacent pits is decreased and high quality readout signal can be obtained. Based on the established simple model of an optical system, the traditional readout signal of super-resolution near-field structure (Super-RENS) disc is simulated according to scalar diffraction theory and angular spectrum method. By comparing simulation results with experimental signals, the validity of the calculation method is proved. Moreover, the differential signal, which is the difference of signals read out by high and low power incident laser, is simulated for single track and three tracks recording pattern. It is shown that, by using the differential readout method, the cross talk from adjacent pits is decreased and high quality readout signal can be obtained.
Acta Optica Sinica
- Publication Date: Jan. 01, 2011
- Vol. 31, Issue 6, 621001 (2011)
Multi-Gray-Level Holographic Storage Using a Binary Spatial Light Modulator
Gu Huarong, Zhao Zhen, Cao Liangcai, He Qingsheng, and Jin Guofan
In order to implement multi-gray-level holographic storage using a binary spatial light modulator,a data page to store is divided into a series of equivalent binary data pages. The recording time is also split into a series of time slices corresponding to the binary data pages. During each time slice,a binary data page is uploaded by the binary spatial light modulator into the object beam which interferes with the reference beam. A series of holograms are recorded in the material. It is proved theoretically that the gray-level distributions of the reconstructed data page are equal to those of the original data page. An experiment of four-gray-level storage is carried out to verify its feasibility. The multi-gray-level storage method can enlarge the capacity of the stored data page. The dynamic range of the material is fully made use of. And the storage density and readout data rate are both improved. In order to implement multi-gray-level holographic storage using a binary spatial light modulator,a data page to store is divided into a series of equivalent binary data pages. The recording time is also split into a series of time slices corresponding to the binary data pages. During each time slice,a binary data page is uploaded by the binary spatial light modulator into the object beam which interferes with the reference beam. A series of holograms are recorded in the material. It is proved theoretically that the gray-level distributions of the reconstructed data page are equal to those of the original data page. An experiment of four-gray-level storage is carried out to verify its feasibility. The multi-gray-level storage method can enlarge the capacity of the stored data page. The dynamic range of the material is fully made use of. And the storage density and readout data rate are both improved.
Acta Optica Sinica
- Publication Date: Jun. 18, 2020
- Vol. 30, Issue 7, 2080 (2010)
Laser Initialization Study of Novel SiSb Phase Change Films
Huang Huan, Wang Yang, and Gan Fuxi
SiSb films are deposited on the polycarbonate optical discs by direct current magnetron sputtering technology. Discs with SiSb films are initialized at laser power 400,500,600,700,800,1200 mW,respectively,by phase change optical disc initializer. The transformation of reflectivity at wavelength from 300 nm to 800 nm of films initialized at different laser power is compared. The results illustrate that reflectivity and reflectivity contrast of SiSb films increase gradually with the enhancement of initializing laser power. Reflectivity contrast of the novel SiSb films initialized at laser power 1200 mW is as high as 30%-35%,which indicates novel SiSb phase change material is a promising material for optical data storage. X-ray diffraction is performed on the as-deposited SiSb films and those laser-initialized at laser power 400,800,1200 mW,respectively. The study shows that the as-deposited SiSb is amorphous state,crystallization to different extent in the samples initialized at different laser power takes place,and the higher the laser power is the higher the degree of crystallization in the samples. Crystallization phase of the samples is hexagonal rhomb-centered structure of antimony,which is similar to the structure of thermal annealing SiSb films reported by other papers. SiSb films are deposited on the polycarbonate optical discs by direct current magnetron sputtering technology. Discs with SiSb films are initialized at laser power 400,500,600,700,800,1200 mW,respectively,by phase change optical disc initializer. The transformation of reflectivity at wavelength from 300 nm to 800 nm of films initialized at different laser power is compared. The results illustrate that reflectivity and reflectivity contrast of SiSb films increase gradually with the enhancement of initializing laser power. Reflectivity contrast of the novel SiSb films initialized at laser power 1200 mW is as high as 30%-35%,which indicates novel SiSb phase change material is a promising material for optical data storage. X-ray diffraction is performed on the as-deposited SiSb films and those laser-initialized at laser power 400,800,1200 mW,respectively. The study shows that the as-deposited SiSb is amorphous state,crystallization to different extent in the samples initialized at different laser power takes place,and the higher the laser power is the higher the degree of crystallization in the samples. Crystallization phase of the samples is hexagonal rhomb-centered structure of antimony,which is similar to the structure of thermal annealing SiSb films reported by other papers.
Acta Optica Sinica
- Publication Date: Jun. 18, 2020
- Vol. 30, Issue 4, 1135 (2010)
Adaptive Level Detection for Multi-Level Optical Disk Using Signal Waveform Modulation
Tang Yi, Pei Jing, Pan Longfa, and Liu Hailong
The partial response maximum like-hood (PRML) can not be directly used for the signal waveform modulation (SWM) multi-level (ML) recording,because in SWM ML,the signal after time recovery does not respond to a symbol sequence. An adaptive level detection method based on minimum Euclid distance is proposed. The Euclid distance between the actual waveform and reference waveform is employed for the level detection. Adaptation can make the set reference waveform approach the actual waveform. The protection mechanism can prevent the case that the reference waveform greatly deviates from the actual. Experimental results show that,without adjusting parameters,this detection method can achieve a low level error ratio,which is less than 2×10-4,for different disk batches. It also has capability for disks with defects. Using this level detection method,the playback system realizes stable and continuous playback of high definition video. The partial response maximum like-hood (PRML) can not be directly used for the signal waveform modulation (SWM) multi-level (ML) recording,because in SWM ML,the signal after time recovery does not respond to a symbol sequence. An adaptive level detection method based on minimum Euclid distance is proposed. The Euclid distance between the actual waveform and reference waveform is employed for the level detection. Adaptation can make the set reference waveform approach the actual waveform. The protection mechanism can prevent the case that the reference waveform greatly deviates from the actual. Experimental results show that,without adjusting parameters,this detection method can achieve a low level error ratio,which is less than 2×10-4,for different disk batches. It also has capability for disks with defects. Using this level detection method,the playback system realizes stable and continuous playback of high definition video.
Acta Optica Sinica
- Publication Date: Jun. 18, 2020
- Vol. 30, Issue 4, 1130 (2010)
Experimental Investigation of Optical Vortex Generated by Volume Holography
Li Hailian, Yang Dexing, Ren Xiaoyuan, and Zhao Jianlin
Complicated optical vortices can be generated by holography and their topological structures could be controlled easily,but the obtained diffraction efficiencies are usually low. It was investigated that optical vortex was stored and reconstructed in LiNbO3:Fe crystal by volume holography. The results exhibit that diffraction efficiency of vortex beam was achieved at 26.7% in a crystal just with a thickness of 0.6 mm,and the quality of reconstructed vortex was almost identical to that of original one. Furthermore,by employing Kogelnik′s coupled-wave theory,the results of numerical computations according to the experimental parameters show that diffraction efficiency of vortex beam could attain to 100% as the thickness of crystal reached 1.23 mm with the same crystal and the same exposure parameters. Complicated optical vortices can be generated by holography and their topological structures could be controlled easily,but the obtained diffraction efficiencies are usually low. It was investigated that optical vortex was stored and reconstructed in LiNbO3:Fe crystal by volume holography. The results exhibit that diffraction efficiency of vortex beam was achieved at 26.7% in a crystal just with a thickness of 0.6 mm,and the quality of reconstructed vortex was almost identical to that of original one. Furthermore,by employing Kogelnik′s coupled-wave theory,the results of numerical computations according to the experimental parameters show that diffraction efficiency of vortex beam could attain to 100% as the thickness of crystal reached 1.23 mm with the same crystal and the same exposure parameters.
Acta Optica Sinica
- Publication Date: Jun. 18, 2020
- Vol. 30, Issue 2, 503 (2010)
Two-Photon Three-Dimensional Optical Data Storage with Equal Exposure Energy and Time Increase
Tang Huohong, Xing Hui, Huang Wenhao, and Zhang Fushi
Intensity of laser focus was simulated in the condition of refractive index mismatch (n=1.48, NA=0.65) at different recording depth with two-photon writing based on Torok’s theory,in order to increase the readout signal intensity of deep layer bits and the memory capacity of two-photon 3D optical data storage. The relationship between the square of the maximum intensity at laser focus and the recording depth was acquired. Based on atomic absorption theory, the relationship between the exposure time and the recording depth in the condition of equal exposure energy without recording power changed was acquired. According to the results and using home-made two-photon 3D optical data memory system, the contrast experiment of recorded bits in eight consecutive layers with equal exposure energy and excitation time increasing was done in a photochromic storage medium. The experimental result indicates that the memory capacity is increased and the readout signal intensity in deep layer is enhanced effectively. Intensity of laser focus was simulated in the condition of refractive index mismatch (n=1.48, NA=0.65) at different recording depth with two-photon writing based on Torok’s theory,in order to increase the readout signal intensity of deep layer bits and the memory capacity of two-photon 3D optical data storage. The relationship between the square of the maximum intensity at laser focus and the recording depth was acquired. Based on atomic absorption theory, the relationship between the exposure time and the recording depth in the condition of equal exposure energy without recording power changed was acquired. According to the results and using home-made two-photon 3D optical data memory system, the contrast experiment of recorded bits in eight consecutive layers with equal exposure energy and excitation time increasing was done in a photochromic storage medium. The experimental result indicates that the memory capacity is increased and the readout signal intensity in deep layer is enhanced effectively.
Acta Optica Sinica
- Publication Date: Jun. 19, 2020
- Vol. 29, Issue 5, 1347 (2009)
Simulation Analysis and Experimental Validation of a New Multi-Level Read-Only Optical Recording Method
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
A multi-level method using wave-shape modulation is presented. In this method, a short pit or land is added to the original marks, which leads to a recognizable “disturbance” in the readout signal and results in wave-shape modulation of readout signal. Using a simplified mastering model and angular-spectrum decomposition-based readout model, this method is simulated on the DVD system. Simulation determines how many levels can be realized for each run-length as well as the writing parameters for each level. Experiments on typical run-length of 6T and 11T are carried out. The readout signal agrees with the simulated one. Level error rates less than 1×10-4 and 1×10-5 are achieved. Experiments validate this new multi-level recording method. A multi-level method using wave-shape modulation is presented. In this method, a short pit or land is added to the original marks, which leads to a recognizable “disturbance” in the readout signal and results in wave-shape modulation of readout signal. Using a simplified mastering model and angular-spectrum decomposition-based readout model, this method is simulated on the DVD system. Simulation determines how many levels can be realized for each run-length as well as the writing parameters for each level. Experiments on typical run-length of 6T and 11T are carried out. The readout signal agrees with the simulated one. Level error rates less than 1×10-4 and 1×10-5 are achieved. Experiments validate this new multi-level recording method.
Acta Optica Sinica
- Publication Date: Jan. 01, 2008
- Vol. 28, Issue 7, 1353 (2008)
Photochemistry Dynamics of Photopolymer Holographic Recording Material Bused on Methylene Blue and Erythrosin B
[in Chinese], [in Chinese], [in Chinese], and [in Chinese]
The photochemical theoretical model and dynamic parameters of the photopolymer are studied. A new holographic photopolymer sensitized by methylene blue (MB) and erythrosine B (ErB) is prepared .This material is tested to obtain transmissivity versus exposure condition and the photochemical parameters with the fixed exposure wavelength of 633nm and intensity of 65 mW/cm2. Experimental results show that photobleaching coefficient k and quantum yield Φ of photopolymer increase with the exposure wavelength and increase of light intensity. At the intensity of 65 mW/cm2 transmissivity drops under short wave, photobleaching coefficient k is negative, but the molar-absorption coefficient ε shows different changes in different conditions. The photochemical theoretical model and dynamic parameters of the photopolymer are studied. A new holographic photopolymer sensitized by methylene blue (MB) and erythrosine B (ErB) is prepared .This material is tested to obtain transmissivity versus exposure condition and the photochemical parameters with the fixed exposure wavelength of 633nm and intensity of 65 mW/cm2. Experimental results show that photobleaching coefficient k and quantum yield Φ of photopolymer increase with the exposure wavelength and increase of light intensity. At the intensity of 65 mW/cm2 transmissivity drops under short wave, photobleaching coefficient k is negative, but the molar-absorption coefficient ε shows different changes in different conditions.
Acta Optica Sinica
- Publication Date: Jan. 01, 2007
- Vol. 27, Issue 9, 1675 (2007)
Synchronizing Focus Error Detection of Dual-Pickup in Multi-Layer Data Storage System
[in Chinese], [in Chinese], [in Chinese], [in Chinese], and [in Chinese]
To implement dual-pickup-head multilayer data storage system, it is necessary to measure the synchronizing focus error of the two pickup heads to validate the feasibility of the focus servo method. By using the ABCD transforming matrix method of the geometric optics, we calculate the relationship between the output energy and the space interval of the two pickup heads. After confirming the detection system working in linear area, the coil motors of the two pickup heads were driven by sine signal with different frequency and record the output signals of the photo-detector under different movement states respectively, such as rest, single pickup head movement and dual-pickup-head synchronizing movement. The synchronizing focus error, which is caused by the characteristic parameter mismatch of the two pickup heads, could be obtained through frequency-domain analysis of these output signals. The experimental result shows that the amplitude of synchronizing focus error under 20 Hz is less than 1 μm, which could satisfy the focus servo requirement of the multilayer data storage system well. To implement dual-pickup-head multilayer data storage system, it is necessary to measure the synchronizing focus error of the two pickup heads to validate the feasibility of the focus servo method. By using the ABCD transforming matrix method of the geometric optics, we calculate the relationship between the output energy and the space interval of the two pickup heads. After confirming the detection system working in linear area, the coil motors of the two pickup heads were driven by sine signal with different frequency and record the output signals of the photo-detector under different movement states respectively, such as rest, single pickup head movement and dual-pickup-head synchronizing movement. The synchronizing focus error, which is caused by the characteristic parameter mismatch of the two pickup heads, could be obtained through frequency-domain analysis of these output signals. The experimental result shows that the amplitude of synchronizing focus error under 20 Hz is less than 1 μm, which could satisfy the focus servo requirement of the multilayer data storage system well.
Acta Optica Sinica
- Publication Date: Jan. 01, 2007
- Vol. 27, Issue 4, 685 (2007)
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