{"title":"Electronics, Optics, and the Photorefractive Effect","authors":"Richard C. Williamson","doi":"10.1364/pmed.1991.tud1","DOIUrl":"https://doi.org/10.1364/pmed.1991.tud1","url":null,"abstract":"Summary not available.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130150473","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}
The paper reviews our studies[1−7] concerned of photoinduced charge dynamics and electric field evolution in the case of external field screening. The experimental methods providing possibility of electric field distribution direct measurements are considered. It is found that there are two different regimes of electric field screening which depend on experimental conditions (kind of crystal, temperature): narrowing of major cariers depletion region and stratification effect (numerous space charge layers of alternating sign) with increasing charge density - regime 1 and the slow broadening of single layer with constant charge density may occur in bulk of a sample - regime 2.These regimes were experimentally investigated in Bi12SiO20, ZnSe and GaAs crystals. A theoretical description is given of a sufficiently general charge transfer model involving the photogeneration of free carriers, their drift and trapping throughout the depth of the material.
{"title":"Charge Transport in High-Resistivity Photorefractive Crystals (Bi12SiO20, ZnSe, GaAs)","authors":"A. Ilinskii","doi":"10.1364/pmed.1991.tuc7","DOIUrl":"https://doi.org/10.1364/pmed.1991.tuc7","url":null,"abstract":"The paper reviews our studies[1−7] concerned of photoinduced charge dynamics and electric field evolution in the case of external field screening. The experimental methods providing possibility of electric field distribution direct measurements are considered. It is found that there are two different regimes of electric field screening which depend on experimental conditions (kind of crystal, temperature): narrowing of major cariers depletion region and stratification effect (numerous space charge layers of alternating sign) with increasing charge density - regime 1 and the slow broadening of single layer with constant charge density may occur in bulk of a sample - regime 2.These regimes were experimentally investigated in Bi12SiO20, ZnSe and GaAs crystals. A theoretical description is given of a sufficiently general charge transfer model involving the photogeneration of free carriers, their drift and trapping throughout the depth of the material.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"95 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116436408","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}
N. Kukhtarev, A. Gnatovskii, Z. Yanchuk, T. Semenets, L. Pryadko, Y. Kargin, K. Ringhofer
We have investigated the new doubly color sensitive photorefractive crystal Bi12Ti0.76V0.24O20 by writing a hologram in green (λ = 0.51 µm, cw-argon laser) and reading it out in red (λ = 0.63 µm, cw-HeNe laser). It was found that the diffraction efficiency for the red beam is chaotically oscillating in time with a period of about 0.1 s between zero and some maximum. The diffraction efficiency for the red beam decayed smoothly after the green beam was switched off. These oscillations exist also for values of the diffraction efficiency as low as 0.1%, and therefore can not be explained by overmodulation of the refractive-index grating.
{"title":"Red-green diffraction instability in the photorefractive mixed crystal Bi12Ti0.76V0.24O20","authors":"N. Kukhtarev, A. Gnatovskii, Z. Yanchuk, T. Semenets, L. Pryadko, Y. Kargin, K. Ringhofer","doi":"10.1364/pmed.1991.mb1","DOIUrl":"https://doi.org/10.1364/pmed.1991.mb1","url":null,"abstract":"We have investigated the new doubly color sensitive photorefractive crystal Bi12Ti0.76V0.24O20 by writing a hologram in green (λ = 0.51 µm, cw-argon laser) and reading it out in red (λ = 0.63 µm, cw-HeNe laser). It was found that the diffraction efficiency for the red beam is chaotically oscillating in time with a period of about 0.1 s between zero and some maximum. The diffraction efficiency for the red beam decayed smoothly after the green beam was switched off. These oscillations exist also for values of the diffraction efficiency as low as 0.1%, and therefore can not be explained by overmodulation of the refractive-index grating.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129322024","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}
W. Schroeder, T. S. Stark, Arthur L. Smir, G. Valley
We use a novel, nondegenerate, polarization-sensitive, transient-grating technique1 to monitor the picosecond dynamics of the photorefractive effect in undoped CdTe and InP:Fe at 960 nm. The technique circumvents the limited temporal resolution of the two-beam coupling geometry by using a time-delayed third probe pulse (with a duration of <5 psec) to read the gratings written in the semiconductor. The technique also exploits the crystal symmetry of zincblende semiconductors by using an optically induced anisotropy in the crystal index of refraction2 to separate the photorefractive gratings from the stronger, co-existing instantaneous bound-electronic and freecarrier gratings. In both semiconductors, the photorefractive effect is associated with the Dember field between mobile electron-hole pairs, in contrast to the more conventional photorefractive space-charge field connected with the separation of a mobile carriers species from a stationary, but oppositely charged, mid-gap state. In the undoped CdTe sample, which possesses no optically-active mid-gap levels, the electron-hole pairs are produced by two-photon absorption of 1.3 eV photons across the 1.44 eV band-gap of the semiconductor. The resultant ~1 eV excess carrier energy, which allows hot carrier transport to dominate the initial formation of the space-charge field, causes up to an order of magnitude enhancement in the photorefractive effect on picosecond timescales. After the carriers have cooled and the initial overshoot in the space-charge field has decayed, the photorefractive effect is observed to decay as the Dember field is destroyed by ambipolar diffusion of the electron-hole pairs across the grating period. In InP:Fe on the other hand, the electron-hole pairs are produced predominantly by direct single-photon band-to-band absorption into the band-tail of the semiconductor (band-gap ~1.35 eV), since the iron dopant only dominates the linear absorption at longer wavelengths. This means that the carriers are generated with little excess energy. Consequently, no hot carrier enhancement of the photorefractive effect was observed, and once formed, the Dember space-charge field decayed directly by ambipolar diffusion.
{"title":"Hot Carrier Enhancement of Dember Photorefractive Space-Charge Fields in Zincblende Semiconductors","authors":"W. Schroeder, T. S. Stark, Arthur L. Smir, G. Valley","doi":"10.1364/pmed.1991.mc5","DOIUrl":"https://doi.org/10.1364/pmed.1991.mc5","url":null,"abstract":"We use a novel, nondegenerate, polarization-sensitive, transient-grating technique1 to monitor the picosecond dynamics of the photorefractive effect in undoped CdTe and InP:Fe at 960 nm. The technique circumvents the limited temporal resolution of the two-beam coupling geometry by using a time-delayed third probe pulse (with a duration of <5 psec) to read the gratings written in the semiconductor. The technique also exploits the crystal symmetry of zincblende semiconductors by using an optically induced anisotropy in the crystal index of refraction2 to separate the photorefractive gratings from the stronger, co-existing instantaneous bound-electronic and freecarrier gratings. In both semiconductors, the photorefractive effect is associated with the Dember field between mobile electron-hole pairs, in contrast to the more conventional photorefractive space-charge field connected with the separation of a mobile carriers species from a stationary, but oppositely charged, mid-gap state. In the undoped CdTe sample, which possesses no optically-active mid-gap levels, the electron-hole pairs are produced by two-photon absorption of 1.3 eV photons across the 1.44 eV band-gap of the semiconductor. The resultant ~1 eV excess carrier energy, which allows hot carrier transport to dominate the initial formation of the space-charge field, causes up to an order of magnitude enhancement in the photorefractive effect on picosecond timescales. After the carriers have cooled and the initial overshoot in the space-charge field has decayed, the photorefractive effect is observed to decay as the Dember field is destroyed by ambipolar diffusion of the electron-hole pairs across the grating period. In InP:Fe on the other hand, the electron-hole pairs are produced predominantly by direct single-photon band-to-band absorption into the band-tail of the semiconductor (band-gap ~1.35 eV), since the iron dopant only dominates the linear absorption at longer wavelengths. This means that the carriers are generated with little excess energy. Consequently, no hot carrier enhancement of the photorefractive effect was observed, and once formed, the Dember space-charge field decayed directly by ambipolar diffusion.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131295603","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}
Photorefractive crystal waveguide(PCW) is a novel approach to enhance the photorefractive effects.1-4 The waveguide geometry provides a tight optical field confinement and long interaction length of waves, resulting in increasing diffraction efficiency and angular sensitivity of hologram. It also allows to synthesize a high-density matrix array. Key issues to gain the practical applicability are how to overcome the drawbacks of PCW such as the finite aperture and modal phase dispersion which affects both image fidelity and holographic storage capacity.
{"title":"Reflection Grating Photorefractive Self-Pumped Ring Mirror","authors":"K. Kitayama, F. Ito","doi":"10.1364/pmed.1991.mc14","DOIUrl":"https://doi.org/10.1364/pmed.1991.mc14","url":null,"abstract":"Photorefractive crystal waveguide(PCW) is a novel approach to enhance the photorefractive effects.1-4 The waveguide geometry provides a tight optical field confinement and long interaction length of waves, resulting in increasing diffraction efficiency and angular sensitivity of hologram. It also allows to synthesize a high-density matrix array. Key issues to gain the practical applicability are how to overcome the drawbacks of PCW such as the finite aperture and modal phase dispersion which affects both image fidelity and holographic storage capacity.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"43 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115152896","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}
T. Volk, M. A. Ivanov, F. Y. Shchapov, N. Rubinina
Photoinduced charge transport in LiNbO3 is defined by presence of a Fe-like impurity, Fe2+ being the donor, Fe3+-the acceptor of electrons1. Two level scheme gives the linear dependence of photoconductivity (that is of inverse response 2 times of photorefraction) on the light intensity2.
{"title":"Photoinduced Charge Transport in Optical Damage Resistant LiNbO3:Me (Me = Mg, Zn)","authors":"T. Volk, M. A. Ivanov, F. Y. Shchapov, N. Rubinina","doi":"10.1364/pmed.1991.tuc25","DOIUrl":"https://doi.org/10.1364/pmed.1991.tuc25","url":null,"abstract":"Photoinduced charge transport in LiNbO3 is defined by presence of a Fe-like impurity, Fe2+ being the donor, Fe3+-the acceptor of electrons1. Two level scheme gives the linear dependence of photoconductivity (that is of inverse response 2 times of photorefraction) on the light intensity2.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129909869","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}
To the best of our knowledge, only preliminary studies of photorefractive effects in the ultraviolet (UV) spectral range have been reported up to now, e.g. in KH2PO4 [1], RbZnBr4 [2] (both at low temperatures), and in LiNbO3 [3, 4] and LiTaO3 [5] in the near UV. Photorefractive materials operating in the UV however could be very useful for all types of coherent optical beam interactions, e.g. beam amplification, dynamical holography, phase-conjugation or photolithographic applications where the use of shorter wavelengths leads to an increased resolution.
{"title":"Photorefractive properties of Bi4Ge3O12 crystals in the ultraviolet spectral range","authors":"G. Montemezzani, Stephan Pfändler, P. Günter","doi":"10.1364/pmed.1991.ma5","DOIUrl":"https://doi.org/10.1364/pmed.1991.ma5","url":null,"abstract":"To the best of our knowledge, only preliminary studies of photorefractive effects in the ultraviolet (UV) spectral range have been reported up to now, e.g. in KH2PO4 [1], RbZnBr4 [2] (both at low temperatures), and in LiNbO3 [3, 4] and LiTaO3 [5] in the near UV. Photorefractive materials operating in the UV however could be very useful for all types of coherent optical beam interactions, e.g. beam amplification, dynamical holography, phase-conjugation or photolithographic applications where the use of shorter wavelengths leads to an increased resolution.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"28 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127713399","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}
A. Gnatovskii, A. Volyar, N. Kukhtarev, S. Lapaeva
We describe the results of the image transmission through the multimode optical fiber and photorefractive crystal LiNbO3:Fe.Experiments were done with HeNe laser (λ =0.63μm), with multimode fiber of 70μm diameter, the aperture number 0.17 and 2m long. After passing an optical fiber light wave E1 were mixed with another coherent wave E2 at the photorefractive crystal. Amplitude mask was introduced in E2 wave and a dynamic hologram was recorded in the crystal through photogalvanṁc effect /1/.Retrieval of this hologram was done by another counterpropagating wave E3, which lead to difracted wave E4 conjugated to E1 with 1⊕% difraction efficiency after 3min. of hologram writing.
{"title":"Image Transmission through Multimode Fiber and the Photorefractive Crystal","authors":"A. Gnatovskii, A. Volyar, N. Kukhtarev, S. Lapaeva","doi":"10.1364/pmed.1991.mc15","DOIUrl":"https://doi.org/10.1364/pmed.1991.mc15","url":null,"abstract":"We describe the results of the image transmission through the multimode optical fiber and photorefractive crystal LiNbO3:Fe.Experiments were done with HeNe laser (λ =0.63μm), with multimode fiber of 70μm diameter, the aperture number 0.17 and 2m long. After passing an optical fiber light wave E1 were mixed with another coherent wave E2 at the photorefractive crystal. Amplitude mask was introduced in E2 wave and a dynamic hologram was recorded in the crystal through photogalvanṁc effect /1/.Retrieval of this hologram was done by another counterpropagating wave E3, which lead to difracted wave E4 conjugated to E1 with 1⊕% difraction efficiency after 3min. of hologram writing.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"225 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116268782","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}
Photoinduced scattering (PS) is inherent in a varying degree in any photorefractive crystal. The origin of the PS is quite clear: this is an amplification of the weak seed scattering. A number of papers, for example [1-3], deal with a description of the effect. The pump and scattered waves supposed usually to have the same frequency. In the framework of that approach, a steady-state PS may only be caused by the nonlocal photorefractive response (i.e. by shifted gratings). However, in many cases experiments show the steady-state PS to be abnormaly large and this can not be accounted for by the nonlocal response. LiNbO3:Pe crystals, where the local response (i.e. unshifted gratings) exceed in value the nonlocal one by 101-102 times, can be pointed out as an example.
{"title":"Low-Frequency Noise and Photoinduced Scattering in Photorefractive Crystals","authors":"B. Sturman","doi":"10.1364/pmed.1991.wa8","DOIUrl":"https://doi.org/10.1364/pmed.1991.wa8","url":null,"abstract":"Photoinduced scattering (PS) is inherent in a varying degree in any photorefractive crystal. The origin of the PS is quite clear: this is an amplification of the weak seed scattering. A number of papers, for example [1-3], deal with a description of the effect. The pump and scattered waves supposed usually to have the same frequency. In the framework of that approach, a steady-state PS may only be caused by the nonlocal photorefractive response (i.e. by shifted gratings). However, in many cases experiments show the steady-state PS to be abnormaly large and this can not be accounted for by the nonlocal response. LiNbO3:Pe crystals, where the local response (i.e. unshifted gratings) exceed in value the nonlocal one by 101-102 times, can be pointed out as an example.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134132735","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}
The fabrication of thin films optical waveguides of photorefractive materials is particularly desirable for applications in integrated optics. It is also of interest because the guided-wave intensity-length product can be considerably larger than in bulk media because of the optical confinement within the waveguide. The increased intensity-length product may therefore allow much faster response times than in the bulk (typically by a factor of ≈103-l04). Thin crystalline films can be fabricated by a variety of techniques such as RF sputtering, flash evaporation, molecular beam epitaxy and liquid phase epitaxy. However, the films grown are often of the incorrect (or variable) composition and phase and are rarely of good optical quality. We discuss here two methods that we have investigated for producing optical waveguides in several different photorefractive materials.
{"title":"Investigation of Photorefractive Waveguides Fabricated by Excimer Laser Ablation and Ion-Implantation","authors":"K. Youden, R. Eason, M. Gower","doi":"10.1364/pmed.1991.wc28","DOIUrl":"https://doi.org/10.1364/pmed.1991.wc28","url":null,"abstract":"The fabrication of thin films optical waveguides of photorefractive materials is particularly desirable for applications in integrated optics. It is also of interest because the guided-wave intensity-length product can be considerably larger than in bulk media because of the optical confinement within the waveguide. The increased intensity-length product may therefore allow much faster response times than in the bulk (typically by a factor of ≈103-l04). Thin crystalline films can be fabricated by a variety of techniques such as RF sputtering, flash evaporation, molecular beam epitaxy and liquid phase epitaxy. However, the films grown are often of the incorrect (or variable) composition and phase and are rarely of good optical quality. We discuss here two methods that we have investigated for producing optical waveguides in several different photorefractive materials.","PeriodicalId":355924,"journal":{"name":"Photorefractive Materials, Effects, and Devices","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123173846","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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