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Partha P. Banerjee - One of the best experts on this subject based on the ideXlab platform.

  • non mechanical beam steering using reflection mode readout of volume gratings in a Photorefractive Material
    Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications XIV, 2020
    Co-Authors: Austin Scott, Partha P. Banerjee, Jonathan E Slagle
    Abstract:

    A method for writing programmable volume phase gratings into Photorefractive Materials using visible wavelengths in a transmission geometry, and then subsequently probing these gratings in a reflection geometry using infrared (IR) wavelengths to achieve specific angles of reflection of the probe beam is analyzed. The programmable features of these gratings include grating spacing and tilt, or K-vector magnitude and orientation. Relationships have been derived between the incidence angles of the writing beams and the corresponding reflection angles of the IR probe beam. More specifically, for a fixed angle of incidence of the probe beam, two unique writing beam angles can be found which generate a grating with the correct spacing and tilt to reflect and steer the probe beam through a wide field of desired angles.

  • Holographic Surface Gratings in Photorefractive Materials
    Frontiers in Optics 2015, 2015
    Co-Authors: Ujitha Abeywickrema, Partha P. Banerjee, Dean R. Evans
    Abstract:

    Existence of surface gratings associated with volume gratings in a Photorefractive Material is proved by analyzing reflected diffraction orders of an incident reading beam. A novel technique is used to numerically eliminate the Fabry-Perot effect from the diffracted orders.

  • Distinction between deterministic and random beam fanning in Photorefractive Materials
    Photorefractive Fiber and Crystal Devices: Materials Optical Properties and Applications XII, 2006
    Co-Authors: Partha P. Banerjee, Arun Mahadevan Venkataraman
    Abstract:

    Photorefractive beam fanning is observed in diffusion dominated Materials such as barium titanate and photovoltaic Materials such as lithium niobate. Beam fanning in barium titanate has been extensively used to generate self-pumped phase conjugation. Beam fanning patterns in lithium niobate have been utilized in characterization of the Photorefractive Material. Two types of beam fanning have been shown to exist: deterministic beam fanning which results from the shape of the beam, and random beam fanning which originates from scattering of the incident beam from the surface and bulk of the crystal 1-4 . In this paper, we report on a careful analysis of both kinds of fanning, using a focused Gaussian beam of varying waists and incorporating randomness in amplitude and phase at the surface and through the bulk of the Photorefractive Material. We show that in Photorefractive barium titanate, deterministic beam fanning, characterized by a deflection of the main lobe of the beam in the far field and an additional sideband, may dominate over waist sizes in the tens of microns, whereas random beam fanning, characterized by multiple lobes, dominate over waist sizes larger than tens of microns.

  • contra directional two beam coupling simulation in a Photorefractive Material using beam propagation
    Frontiers in Optics, 2005
    Co-Authors: Mohammad A Saleh, Partha P. Banerjee, Gary Cook, Jennifer L Carns, Dean R. Evans
    Abstract:

    By using split-step beam propagation method, self-pumped contra-directional two-beam coupling is simulated in a Photorefractive medium for arbitrary shaped beams. The role of diffusion, photovoltaic effect and dark conductivity is investigated for a LiNbO3:Fe crystal.

  • investigation of the self pumped two beam coupling in a Photorefractive Material using beam propagation simulation
    Bulletin of the American Physical Society, 2005
    Co-Authors: Mohammad Saleh, Partha P. Banerjee, Gary Cook, Shekhar Guha, Dean R. Evans
    Abstract:

    Abstract : - At this point we are capable of stimulating the self-pumped contra-directional two-beam coupling in a Photorefractive medium with arbitrary shaped beams. - Our simulation shows positive role of the photovoltaic effect in self-pumped contra-directional TBC, in agreement with experimental observation.

Nakjoong Kim - One of the best experts on this subject based on the ideXlab platform.

  • Application to Optically Controlled Spatial Light Modulator Using Organic Photorefractive Composite
    Polymer Journal, 2004
    Co-Authors: Won-jae Joo, Nakjoong Kim
    Abstract:

    Optically controlled spatial light modulator was demonstrated as application of Photorefractive polymeric Material. Photorefractive composites based on photoconducting carbazole-substituted polysiloxane matrix (PSX-Cz) show an excellent stability against phase separation, compared to poly( N -vinyl carbazole) based composite. 2-[3-[( E )-2-(piperidino)-1-ethenyl]-5,5-dimethyl-2-cyclohexenyliden] malononitrile (P-IP-DC) has large dipole moment and large polarizability anisotropy. A Photorefractive sample in which a chromophore (P-IP-DC) was dispersed showed a high diffraction efficiency of 85% at an external field of 28 V/μm. Application of Photorefractive Material for the optically controlled spatial light modulator which can convert incoherent optical image imposed in Xe-lamp light into coherent image in He–Ne laser wavelength is demonstrated using this composite.

  • Space-charge field in polymeric Photorefractive Material
    Organic Holographic Materials and Applications, 2003
    Co-Authors: Won-jae Joo, Nakjoong Kim
    Abstract:

    We proposed a method for measuring the magnitude of the space-charge field of the polymeric Photorefractive Materials. In the case of polymeric Photorefractive Material with low glass transition temperature, optically anisotropic chromophores are known to be reoriented under space-charge field. Simply by adding a pair of crossed polarizers unit to a conventional degenerated four wave mixing setup, we could measure the birefringence of the Photorefractive Materials induced by a newly formed space-charge field. Since the birefringence of a given Material is governed by the applied electric field, the space-charge field can be determined from the variation of birefringence using the oriented gas model. We investigated the dependence of the grating formation on temperature in Photorefractive polymeric composite, especially the index contrast of the grating. The diffraction efficiency of the Photorefractive polymeric composite decreased with increasing the temperature, and it could be explained with the magnitude of space-charge field and the electro-optic behavior at various temperatures.

  • applications of polymeric Photorefractive Material to reversible data storage and information processing
    Journal of Applied Polymer Science, 2003
    Co-Authors: Hyunaee Chun, Won-jae Joo, In Kyu Moon, Nam-jun Kim, Nakjoong Kim
    Abstract:

    A polymeric Photorefractive composite was prepared from a mixture of carbazole-substituted polysilox- ane as a photoconducting medium, 2,4,7-trinitro-9-flu- orenone as a photosensitizer, and 2-{3-((E)-2-(dibutylamino)- 1-ethenyl)-5,5-dimethyl-2-cyclohexenyliden} malononitrile as an optically nonlinear chromophore. This polymeric com- posite, with a thickness of 100 m, exhibited a high diffrac- tion efficiency of 92% at a low applied electric field of 30 V/m, which corresponded a refractive index modulation of 3 10 3 . Applications of this polymeric composite to reversible holographic data storage and pattern recognition were demonstrated. The three-dimensional image was re- corded on our Photorefractive film at an applied field of 30 V/m, and subsequently, a high quality image was recon- structed in a real-time operation. Pattern recognition was successfully demonstrated based on a joint-transform opti- cal correlation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 368 -372, 2003

  • Dependence of the Bragg condition on an external electric field for a polymeric Photorefractive Material
    Applied optics, 2003
    Co-Authors: Won-jae Joo, Hyunaee Chun, In Kyu Moon, Nakjoong Kim
    Abstract:

    We investigated the effect of an applied electric field on the Bragg condition of degenerate four-wave mixing in a polymeric Photorefractive Material with a low glass-transition temperature. For a polymeric Photorefractive Material the application of an external electric field as is necessary for photorefractivity leads to birefringence of the Material by poling of the nonlinear optical chromophore. Because the propagation vectors of the pumping and reading beams inside the Material are influenced by the refractive index of the Material, the Bragg condition depends on the magnitude of the external field. Using an oriented gas model and the-coupled-mode theory, we numerically analyzed the Bragg-mismatch effect that causes a reduction in diffraction efficiency as a function of an external field. We present the boundary conditions for sample thickness and grating spacing for which the Bragg-mismatch effect must be taken into account.

  • Determination of the space-charge field in polymeric Photorefractive Material
    Journal of Applied Physics, 2002
    Co-Authors: Won-jae Joo, Hyunaee Chun, In Kyu Moon, Nam-jun Kim, Nakjoong Kim
    Abstract:

    We proposed a method for measuring the magnitude of the space-charge field of the polymeric Photorefractive Materials. In the case of polymeric Photorefractive Material with low glass transition temperature, optically anisotropic chromophores are known to be reoriented under space-charge field. Simply by adding a pair of crossed polarizer units to a conventional degenerated four wave mixing setup, we could measure the birefringence of the Photorefractive Materials induced by a newly formed space-charge field. Since the birefringence of a given Material is governed by the applied electric field, the space-charge field can be determined from the variation of birefringence using the oriented gas model.

Amnon Yariv - One of the best experts on this subject based on the ideXlab platform.

  • Steady-state spatial screening solitons in Photorefractive Materials with external applied field.
    Physical review letters, 1994
    Co-Authors: Mordechai Segev, B Crosignani, George C. Valley, Paolo Diporto, Amnon Yariv
    Abstract:

    Steady-state dark (bright) planar spatial solitons are predicted for Photorefractive Materials when the diffraction of an optical beam is exactly compensated by nonlinear self-defocusing (focusing), due to the screening field set up around a dark notch (or a bright beam) in a Photorefractive Material to which an external field is applied. These screening solitons appear in steady state and differ from previously observed spatial solitons in their properties and physical origin.

  • observation of self trapping of an optical beam due to the Photorefractive effect
    Quantum Electronics and Laser Science Conference, 1993
    Co-Authors: Galen Duree, J L Shultz, Gregory J Salamo, Mordechai Segev, Amnon Yariv, B Crosignani, Paolo Di Porto, Edward J Sharp, Ratnakar R Neurgaonkar
    Abstract:

    Recently, a new type of spatial soliton has been predicted to be observable in a Photorefractive crystal.1,2 For example, consider an input laser beam that is diverging because of diffraction as it passes through a Photorefractive Material. Interference between the beam’s spatial-frequency components can be considered to write Photorefractive gratings on the crystal. These gratings, or spatial variations in the index of refraction, have one component that is in phase and another that is 90° out of phase with their parent intensity pattern.

  • characterization of a new Photorefractive Material k sub 1 y l sub y t sub 1 x n sub x
    1992
    Co-Authors: Aharon J. Agranat, Rudy Hofmeister, Victor Leyva, Amnon Yariv
    Abstract:

    Abstract : We have demonstrated the growth of a new Photorefractive Material, KLTN, and have characterized its Photorefractive properties. The crystal was of good quality with a phase transition at 178 (dot) K. It displayed a strong quadratic Photorefractive effect with a sensitivity of 0.0000724. The maximum diffraction efficiency observed was 75% with a corresponding coupling constant of Gamma = 1.75/cm. The writing times were given by tau sub write = 6 sec-sq.cm/W, and there was a strong read/write time asymmetry. The Photorefractive process was shown to be voltage 'controllable. Based on this work, KLTNs seem to be highly promising Materials for volume hologram storage applications.

  • Characterization of a new Photorefractive Material: Kl-yLyT1-xNx
    Optics letters, 1992
    Co-Authors: Aharon J. Agranat, Rudy Hofmeister, Amnon Yariv
    Abstract:

    We report the growth and characterization of a new Photorefractive Material, potassium lithium tantalate niobate (KLTN). A KLTN crystal doped with copper is demonstrated to yield high diffraction efficiency of Photorefractive gratings in the paraelectric phase. Voltage-controllable index gratings with n, = 8.5 x 10^-5 were achieved, which yielded diffraction efficiencies of 75% in a 2.9-mm-thick sample. In addition, diffraction was observed in the paraelectric phase without an applied field. This effect is attributed to a growth-induced strain field.

John K. Mciver - One of the best experts on this subject based on the ideXlab platform.

  • Effects of a single optical beam on Photorefractive Materials: steady-state solution
    Journal of the Optical Society of America B, 1992
    Co-Authors: David Statman, John K. Mciver
    Abstract:

    The band transport model describes charge statics and dynamics within Photorefractive Materials. Here a steady-state solution is found for the setting in which an arbitrary optical beam illuminates a Photorefractive Material. The specific case of a Gaussian beam is investigated. The effects of intensity and beam waist are discussed. A comparison is made with previous studies of this problem. It is found that, when the rate of photoexcitation is less than that of thermal excitation, the band transport model can be linearized. In this case the charge density and the space-charge field are proportional to the intensity of the light. On the other hand, when the rate of photoexcitation is greater than that of thermal excitation, the linear solution to the band transport model no longer applies. In this case the charge density and the space-charge field are independent of the intensity and dependent only on the size of the beam waist.

Won-jae Joo - One of the best experts on this subject based on the ideXlab platform.

  • Application to Optically Controlled Spatial Light Modulator Using Organic Photorefractive Composite
    Polymer Journal, 2004
    Co-Authors: Won-jae Joo, Nakjoong Kim
    Abstract:

    Optically controlled spatial light modulator was demonstrated as application of Photorefractive polymeric Material. Photorefractive composites based on photoconducting carbazole-substituted polysiloxane matrix (PSX-Cz) show an excellent stability against phase separation, compared to poly( N -vinyl carbazole) based composite. 2-[3-[( E )-2-(piperidino)-1-ethenyl]-5,5-dimethyl-2-cyclohexenyliden] malononitrile (P-IP-DC) has large dipole moment and large polarizability anisotropy. A Photorefractive sample in which a chromophore (P-IP-DC) was dispersed showed a high diffraction efficiency of 85% at an external field of 28 V/μm. Application of Photorefractive Material for the optically controlled spatial light modulator which can convert incoherent optical image imposed in Xe-lamp light into coherent image in He–Ne laser wavelength is demonstrated using this composite.

  • Space-charge field in polymeric Photorefractive Material
    Organic Holographic Materials and Applications, 2003
    Co-Authors: Won-jae Joo, Nakjoong Kim
    Abstract:

    We proposed a method for measuring the magnitude of the space-charge field of the polymeric Photorefractive Materials. In the case of polymeric Photorefractive Material with low glass transition temperature, optically anisotropic chromophores are known to be reoriented under space-charge field. Simply by adding a pair of crossed polarizers unit to a conventional degenerated four wave mixing setup, we could measure the birefringence of the Photorefractive Materials induced by a newly formed space-charge field. Since the birefringence of a given Material is governed by the applied electric field, the space-charge field can be determined from the variation of birefringence using the oriented gas model. We investigated the dependence of the grating formation on temperature in Photorefractive polymeric composite, especially the index contrast of the grating. The diffraction efficiency of the Photorefractive polymeric composite decreased with increasing the temperature, and it could be explained with the magnitude of space-charge field and the electro-optic behavior at various temperatures.

  • applications of polymeric Photorefractive Material to reversible data storage and information processing
    Journal of Applied Polymer Science, 2003
    Co-Authors: Hyunaee Chun, Won-jae Joo, In Kyu Moon, Nam-jun Kim, Nakjoong Kim
    Abstract:

    A polymeric Photorefractive composite was prepared from a mixture of carbazole-substituted polysilox- ane as a photoconducting medium, 2,4,7-trinitro-9-flu- orenone as a photosensitizer, and 2-{3-((E)-2-(dibutylamino)- 1-ethenyl)-5,5-dimethyl-2-cyclohexenyliden} malononitrile as an optically nonlinear chromophore. This polymeric com- posite, with a thickness of 100 m, exhibited a high diffrac- tion efficiency of 92% at a low applied electric field of 30 V/m, which corresponded a refractive index modulation of 3 10 3 . Applications of this polymeric composite to reversible holographic data storage and pattern recognition were demonstrated. The three-dimensional image was re- corded on our Photorefractive film at an applied field of 30 V/m, and subsequently, a high quality image was recon- structed in a real-time operation. Pattern recognition was successfully demonstrated based on a joint-transform opti- cal correlation. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 368 -372, 2003

  • Dependence of the Bragg condition on an external electric field for a polymeric Photorefractive Material
    Applied optics, 2003
    Co-Authors: Won-jae Joo, Hyunaee Chun, In Kyu Moon, Nakjoong Kim
    Abstract:

    We investigated the effect of an applied electric field on the Bragg condition of degenerate four-wave mixing in a polymeric Photorefractive Material with a low glass-transition temperature. For a polymeric Photorefractive Material the application of an external electric field as is necessary for photorefractivity leads to birefringence of the Material by poling of the nonlinear optical chromophore. Because the propagation vectors of the pumping and reading beams inside the Material are influenced by the refractive index of the Material, the Bragg condition depends on the magnitude of the external field. Using an oriented gas model and the-coupled-mode theory, we numerically analyzed the Bragg-mismatch effect that causes a reduction in diffraction efficiency as a function of an external field. We present the boundary conditions for sample thickness and grating spacing for which the Bragg-mismatch effect must be taken into account.

  • Determination of the space-charge field in polymeric Photorefractive Material
    Journal of Applied Physics, 2002
    Co-Authors: Won-jae Joo, Hyunaee Chun, In Kyu Moon, Nam-jun Kim, Nakjoong Kim
    Abstract:

    We proposed a method for measuring the magnitude of the space-charge field of the polymeric Photorefractive Materials. In the case of polymeric Photorefractive Material with low glass transition temperature, optically anisotropic chromophores are known to be reoriented under space-charge field. Simply by adding a pair of crossed polarizer units to a conventional degenerated four wave mixing setup, we could measure the birefringence of the Photorefractive Materials induced by a newly formed space-charge field. Since the birefringence of a given Material is governed by the applied electric field, the space-charge field can be determined from the variation of birefringence using the oriented gas model.