Holographic volume data storage has long been an intriguing subject of research interest. The main reason for this interest is the promise of enormous data storage capacities. In a long volume, storage of 1012 bits or more is possible using visible light (1). However, to date, all attempts at attaining and demonstrating a volume holographic data storage system of this density have fallen far short of this theoretical limit (2-6). Although materials limitations contributed to this shortcoming, of more fundamental importance, however, were the problems associated with the angular multiplexing schemes used to holographically access the volume of the storage medium (7-9).
{"title":"High Resolution Volume Holography using Orthogonal Data Storage","authors":"A. Yariv, G. Rakuljic, V. Leyva","doi":"10.1364/pmed.1991.md3","DOIUrl":"https://doi.org/10.1364/pmed.1991.md3","url":null,"abstract":"Holographic volume data storage has long been an intriguing subject of research interest. The main reason for this interest is the promise of enormous data storage capacities. In a long volume, storage of 1012 bits or more is possible using visible light (1). However, to date, all attempts at attaining and demonstrating a volume holographic data storage system of this density have fallen far short of this theoretical limit (2-6). Although materials limitations contributed to this shortcoming, of more fundamental importance, however, were the problems associated with the angular multiplexing schemes used to holographically access the volume of the storage medium (7-9).","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132329649","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optical real-time image processing by spatial light modulators (SLM’s) that utilize photorefractive crystals has attracted much attention /1/. The two-wave mixing SLM is based on the selective spatial erasure of the uniform phase volume hologram created by the two plane coherent beams using an incoherent image bearing beam Iinc(r→) resulting in an additional spatial modulation of the refractive index distribution I1(r→) (commonly with a greater spatial period then the grating period of the hologram). The parameters of these Bragg-type SLM’s are strongly determined by the diffraction properties of the nonuniform volume gratings and are analyzed here by means of the two-wave mixing coupled-wave formalism in it’s two-dimensional description /2/.
{"title":"Image-degradation in a two-wave mixing spatial-light modulator","authors":"G. Notni, R. Kowarschik","doi":"10.1364/pmed.1991.mb7","DOIUrl":"https://doi.org/10.1364/pmed.1991.mb7","url":null,"abstract":"Optical real-time image processing by spatial light modulators (SLM’s) that utilize photorefractive crystals has attracted much attention /1/. The two-wave mixing SLM is based on the selective spatial erasure of the uniform phase volume hologram created by the two plane coherent beams using an incoherent image bearing beam Iinc(r→) resulting in an additional spatial modulation of the refractive index distribution I1(r→) (commonly with a greater spatial period then the grating period of the hologram). The parameters of these Bragg-type SLM’s are strongly determined by the diffraction properties of the nonuniform volume gratings and are analyzed here by means of the two-wave mixing coupled-wave formalism in it’s two-dimensional description /2/.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123645931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent studies of the photorefractive response of CdTe have demonstrated it to be a highly sensitive material with a broad near infrared sensitivity extending to beyond 1.5 μm[1,2]. Desirable parameters, such as large electrooptic coefficient, small dielectric constant, large carrier mobility and availability in semi-insulating form, makes CdTe a potential material of choice for many applications[3]. This study focuses on photorefractive characterization of Bridgeman grown crystals with the goal of providing the information that can lead to the optimization of key photorefractive parameters. We have observed gain and broad sensitivity (1-1.5 μm) in vanadium doped CdTe and Cd0.96Zn0.4Te samples. Mixed alloys such as CdZnTe and CdMnTe allow band gap engineering such that the sensitivity range could be tuned toward the visible and be matched to the wavelength of interest. An applied alternating (AC) field gain enhancement technique is used to demonstrate net gain which is a prerequisite for coherent amplification and self-pumped phase conjugation.
{"title":"Photorefractive properties and alternating electric field gain enhancement of vanadium-doped cadmium telluride and related compounds","authors":"M. Ziari, W. Steier","doi":"10.1364/pmed.1991.tua6","DOIUrl":"https://doi.org/10.1364/pmed.1991.tua6","url":null,"abstract":"Recent studies of the photorefractive response of CdTe have demonstrated it to be a highly sensitive material with a broad near infrared sensitivity extending to beyond 1.5 μm[1,2]. Desirable parameters, such as large electrooptic coefficient, small dielectric constant, large carrier mobility and availability in semi-insulating form, makes CdTe a potential material of choice for many applications[3]. This study focuses on photorefractive characterization of Bridgeman grown crystals with the goal of providing the information that can lead to the optimization of key photorefractive parameters. We have observed gain and broad sensitivity (1-1.5 μm) in vanadium doped CdTe and Cd0.96Zn0.4Te samples. Mixed alloys such as CdZnTe and CdMnTe allow band gap engineering such that the sensitivity range could be tuned toward the visible and be matched to the wavelength of interest. An applied alternating (AC) field gain enhancement technique is used to demonstrate net gain which is a prerequisite for coherent amplification and self-pumped phase conjugation.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"226 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133612312","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Geometry for conjugation of mutually incoherent laser beams, consisting of two interconnected passive ring mirrors, was proposed in Ref.[1]. This is the only geometry among all known mutual conjugators, that can work equally well with either transmission, or reflection gratings recording. A detailed theory of this geometry and its experimental realization in the photorefractive SBN crystal in the case, when transmission gratings were operating, can be found in Ref.[1]. Here we report on the experimental investigation of a reflection grating mutual conjugator in the geometry of two interconnected ring mirrors in cw regime with the characteristic relaxation times of the order of several milliseconds.
{"title":"Reflection Grating Mutual Conjugator in the Geometry of Two Interconnected Ring Mirrors","authors":"A. V. Mamaev, A. Zozulya","doi":"10.1364/pmed.1991.wa1","DOIUrl":"https://doi.org/10.1364/pmed.1991.wa1","url":null,"abstract":"Geometry for conjugation of mutually incoherent laser beams, consisting of two interconnected passive ring mirrors, was proposed in Ref.[1]. This is the only geometry among all known mutual conjugators, that can work equally well with either transmission, or reflection gratings recording. A detailed theory of this geometry and its experimental realization in the photorefractive SBN crystal in the case, when transmission gratings were operating, can be found in Ref.[1]. Here we report on the experimental investigation of a reflection grating mutual conjugator in the geometry of two interconnected ring mirrors in cw regime with the characteristic relaxation times of the order of several milliseconds.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"2012 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131909326","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Signal processing in photorefractive crystals is complicated by photorefractive amplified scattering (fanning). The scattering centers responsible for seeding the fanning noise may be presumed to be traceable to crystal lattice irregularities. These defects have not yet been examined in any great detail, and the relative importance of various specific imperfections and the role they play in the crystal optics are not known. An understanding of these defects should lead to improvement in signal processing through growth of more satisfactory photorefractive crystals. We have set out to address these problems through direct, in situ observation of photorefractive crystals and their gratings in barium titanate by high resolution monochromatic synchrotron x-ray diffraction imaging. The results that we report here indicate the nature of the principal limiting imperfections and demonstrate the feasability of direct observation of photorefractive gratings and scattering centers.
{"title":"Syncnrotron X-ray Diffraction Imaging of Photorefractive Crystals","authors":"G. Fogarty, M. Cronin-Golomb","doi":"10.1364/pmed.1991.tua7","DOIUrl":"https://doi.org/10.1364/pmed.1991.tua7","url":null,"abstract":"Signal processing in photorefractive crystals is complicated by photorefractive amplified scattering (fanning). The scattering centers responsible for seeding the fanning noise may be presumed to be traceable to crystal lattice irregularities. These defects have not yet been examined in any great detail, and the relative importance of various specific imperfections and the role they play in the crystal optics are not known. An understanding of these defects should lead to improvement in signal processing through growth of more satisfactory photorefractive crystals. We have set out to address these problems through direct, in situ observation of photorefractive crystals and their gratings in barium titanate by high resolution monochromatic synchrotron x-ray diffraction imaging. The results that we report here indicate the nature of the principal limiting imperfections and demonstrate the feasability of direct observation of photorefractive gratings and scattering centers.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128100136","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An investigation of self-pumped phase conjugation in barium titanate is made using nanosecond pulses (15 ns) derived from a repetitively pulsed (10 Hz) and frequency-doubled Nd:YAG laser system (532 nm wavelength). It is experimentally shown that high reflectivity (> 20 %) can be achieved. It is also shown that there is a progressive decrease in the reflectivity of both the corner-pumped and ring-passive geometries at pulse intensities of > 4 MW/cm2. At these intensity levels a high photo-carrier population is induced, altering the relative concentrations of Fe2+ and Fe3+ centres and leading to a strong intensity-dependent competition between hole and electron photoconductivity.
{"title":"Self-Pumped Phase Conjugation in Barium Titanate with High Intensity Nanosecond Pulses","authors":"M. Damzen, N. Barry","doi":"10.1364/pmed.1991.wc2","DOIUrl":"https://doi.org/10.1364/pmed.1991.wc2","url":null,"abstract":"An investigation of self-pumped phase conjugation in barium titanate is made using nanosecond pulses (15 ns) derived from a repetitively pulsed (10 Hz) and frequency-doubled Nd:YAG laser system (532 nm wavelength). It is experimentally shown that high reflectivity (> 20 %) can be achieved. It is also shown that there is a progressive decrease in the reflectivity of both the corner-pumped and ring-passive geometries at pulse intensities of > 4 MW/cm2. At these intensity levels a high photo-carrier population is induced, altering the relative concentrations of Fe2+ and Fe3+ centres and leading to a strong intensity-dependent competition between hole and electron photoconductivity.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"49 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120995870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. H. Garrett, J. Chang, P. Tayebati, H. Jenssen, C. Warde
The photorefractive properties of cobaltdoping barium titanate have been recently reported by Rytz et al. [1]. High beam coupling gains were reported therein. Similarly, we have grown a series of cobalt-doped p-type barium titanate crystals, (undoped, 17 ppm, 50 ppm and 75 ppm), that also have relatively large beam coupling gains, e.g. for E||a and kg||c the gain is 7.4 cm−1 at 514.5 nm in the 75 ppm sample. We have further characterized these crystals by determining the sublinear dependence of the response time on intensity, the asymmetry of the beam coupling gain for ±C-axis crystal orientations, (i.e. electrooptic and absorptive coupling), intensity dependence of the gain, and light-induced dark decays. Experimental results indicate that, as the cobalt concentration is increased, the photorefractive character of the crystals change from "type B" to "type A" as defined by Mahgerefteh and Feinberg [2]. Type A crystals have filled hole-shallow traps and type B crystals have partially filled hole-shallow traps and thus low and high dark conductivity respectively.
{"title":"The Influence of Cobalt Doping on Deep and Shallow Trap Dependent Photorefractive Properties of Barium Titanate","authors":"M. H. Garrett, J. Chang, P. Tayebati, H. Jenssen, C. Warde","doi":"10.1364/pmed.1991.mc2","DOIUrl":"https://doi.org/10.1364/pmed.1991.mc2","url":null,"abstract":"The photorefractive properties of cobaltdoping barium titanate have been recently reported by Rytz et al. [1]. High beam coupling gains were reported therein. Similarly, we have grown a series of cobalt-doped p-type barium titanate crystals, (undoped, 17 ppm, 50 ppm and 75 ppm), that also have relatively large beam coupling gains, e.g. for E||a and kg||c the gain is 7.4 cm−1 at 514.5 nm in the 75 ppm sample. We have further characterized these crystals by determining the sublinear dependence of the response time on intensity, the asymmetry of the beam coupling gain for ±C-axis crystal orientations, (i.e. electrooptic and absorptive coupling), intensity dependence of the gain, and light-induced dark decays. Experimental results indicate that, as the cobalt concentration is increased, the photorefractive character of the crystals change from \"type B\" to \"type A\" as defined by Mahgerefteh and Feinberg [2]. Type A crystals have filled hole-shallow traps and type B crystals have partially filled hole-shallow traps and thus low and high dark conductivity respectively.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115487159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
For real-time optical image storage and processing, we have systematically studied self-pumped phase conjugation (SPPC) [1] in barium titanate (BaTiO3) crystals (from Sanders Associates Inc., Merrimack, NH) in terms of the incident angle θ, the impact position l on the crystal surface, the distance L between the imaging lens and the impact point on the crystal face [Figure 1], the argon-ion laser power P (p-wave with various wavelengths), and the ambient temperature T. We found that the stability of the temporal SPPC intensity IPC (t) strongly depends on these geometrical parameters, θ, l, and L. The objective in this paper is to identify optimal conditions in order to stablize and maximize the temporal evolution of the SPPC reflectivity R(t) which is defined as the ratio of IPC (t) to the intensity IM retro-reflected by a mirror at the position of the crystal to the detector. We have defined the optimal (or stable) condition for the SPPC as |Rmax-R(t)|/Rmax ≤ 0.1, where Rmax is the maximum value of R(t) (recorded within 10 minutes to 1 hour) and also the maximum value in terms of the above geometrical and physical parameters.
{"title":"Stability of Information Readout by Self-pumped Phase Conjugation in Barium Titanate","authors":"F. Lin, D. Sun, G. Leu, M. Fiddy, T. Yang","doi":"10.1364/pmed.1991.wc13","DOIUrl":"https://doi.org/10.1364/pmed.1991.wc13","url":null,"abstract":"For real-time optical image storage and processing, we have systematically studied self-pumped phase conjugation (SPPC) [1] in barium titanate (BaTiO3) crystals (from Sanders Associates Inc., Merrimack, NH) in terms of the incident angle θ, the impact position l on the crystal surface, the distance L between the imaging lens and the impact point on the crystal face [Figure 1], the argon-ion laser power P (p-wave with various wavelengths), and the ambient temperature T. We found that the stability of the temporal SPPC intensity IPC (t) strongly depends on these geometrical parameters, θ, l, and L. The objective in this paper is to identify optimal conditions in order to stablize and maximize the temporal evolution of the SPPC reflectivity R(t) which is defined as the ratio of IPC (t) to the intensity IM retro-reflected by a mirror at the position of the crystal to the detector. We have defined the optimal (or stable) condition for the SPPC as |Rmax-R(t)|/Rmax ≤ 0.1, where Rmax is the maximum value of R(t) (recorded within 10 minutes to 1 hour) and also the maximum value in terms of the above geometrical and physical parameters.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122539861","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recently, electron-hole transport in photorefractive media has received much interest. Many observations which cannot be accounted for by simple single-carrier single-level transport can be explained by electron-hole transport. This summary describes electron-hole transport by two different models and describes a regime in which both models give similar results.
{"title":"Electron-Hole—Transport in Photorefractive Media","authors":"M. C. Bradshaw, T. Ma, R. Barker","doi":"10.1364/pmed.1991.wb4","DOIUrl":"https://doi.org/10.1364/pmed.1991.wb4","url":null,"abstract":"Recently, electron-hole transport in photorefractive media has received much interest. Many observations which cannot be accounted for by simple single-carrier single-level transport can be explained by electron-hole transport. This summary describes electron-hole transport by two different models and describes a regime in which both models give similar results.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124852359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Picosecond-pulse laser excitation was used to establish and probe refractive index gratings in KNbO3, KTaO3, and mixed crystals of KTa1-xNbxO3. The purpose of this work was first to identify the physical processes contributing to fast nonlinear optical responses in these samples, and second to determine how these processes evolve with time into the space-charge field photorefractive effect observed with continuous wave excitation. The techniques of pulse-probe degenerate four-wave mixing and nondegenerate four-wave mixing with a continuous wave probe laser were both employed to obtain information about the photorefractive processes that take place after fast pulse excitation. The measurements were made as a function of laser fluence, crossing angle of the write beams, sample orientation with respect to the grating wavevector, polarization directions of the write and probe beams, and write beam wavelength. Mixed crystals with the niobium concentration parameter x varying from 0 to 1.0 were investigated along with KNbO3 samples containing a variety of dopant ions.
{"title":"Picosecond Nonlinear Optical Responses in Photorefractive Crystals","authors":"Huimin Liu, R. Reeves, R. Powell","doi":"10.1364/pmed.1991.wc1","DOIUrl":"https://doi.org/10.1364/pmed.1991.wc1","url":null,"abstract":"Picosecond-pulse laser excitation was used to establish and probe refractive index gratings in KNbO3, KTaO3, and mixed crystals of KTa1-xNbxO3. The purpose of this work was first to identify the physical processes contributing to fast nonlinear optical responses in these samples, and second to determine how these processes evolve with time into the space-charge field photorefractive effect observed with continuous wave excitation. The techniques of pulse-probe degenerate four-wave mixing and nondegenerate four-wave mixing with a continuous wave probe laser were both employed to obtain information about the photorefractive processes that take place after fast pulse excitation. The measurements were made as a function of laser fluence, crossing angle of the write beams, sample orientation with respect to the grating wavevector, polarization directions of the write and probe beams, and write beam wavelength. Mixed crystals with the niobium concentration parameter x varying from 0 to 1.0 were investigated along with KNbO3 samples containing a variety of dopant ions.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1992-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128733692","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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