Role Of Diffusive, Photovoltaic, And Thermal Effects In Beam Fanning In Linbo3, 2016 University of Alabama, Huntsville

#### Role Of Diffusive, Photovoltaic, And Thermal Effects In Beam Fanning In Linbo3, Jaw-Jueh Liu, Partha P. Banerjee, Q. W. Song

*Partha Banerjee*

We analyze the steady-state (Gaussian) beam fanning in LiNbO3 from the nonlinearly coupled Kukhtarev equations by including both diffusive and photovoltaic effects and by adding the thermal effect in the calculation. There is good agreement between theory and experiment. The results show a symmetric beam-fanning pattern whose size depends on the beam waist and the power. Possible applications of our results in nondestructive testing of material parameters and optical limiting are discussed.

Self‐Refraction Of Nonlinear Capillary‐Gravity Waves, 2016 University of Dayton

#### Self‐Refraction Of Nonlinear Capillary‐Gravity Waves, Partha P. Banerjee, Adrianus Korpel, Karl E. Lonngren

*Partha Banerjee*

Self‐refraction effects have been observed during the propagation of deep‐water capillary‐gravity waves. The observations are shown to be in qualitative agreement with the theory of self‐focusing and defocusing in a cubically nonlinear medium in the presence of diffraction.

Single-Beam Holographic Tomography Creates Images In Three Dimensions, 2016 The Catholic University of America

#### Single-Beam Holographic Tomography Creates Images In Three Dimensions, George Nehmetallah, Partha P. Banerjee, Nickolai Kukhtarev

*Partha Banerjee*

In digital holography (DH), the interference between light scattered from an object and a reference wave is recorded using a CCD camera. DH has various advantages over analog holography: no film processing is needed, reconstruction is performed using numerical methods, and no further experimental setup is necessary. However, one of the disadvantages of DH is that current CCDs have a resolution of approximately 1,000 lines/mm, which is less than that of photographic film.

Subharmonic Generation By Resonant Three‐Wave Interaction Of Deep‐Water Capillary Waves, 2016 University of Dayton

#### Subharmonic Generation By Resonant Three‐Wave Interaction Of Deep‐Water Capillary Waves, Partha P. Banerjee, Adrianus Korpel

*Partha Banerjee*

Subharmonic generation has been observed during the propagation of deep‐water capillary waves. The observations are shown to be in agreement with the theory of degenerate resonant noncollinear three‐wave interaction in a nonlinear, dispersive medium.

Self-Enhancement Of Dynamic Gratings In Photogalvanic Crystals, 2016 Alabama A & M University

#### Self-Enhancement Of Dynamic Gratings In Photogalvanic Crystals, Nickolai Kukhtarev, Sergei F. Lyuksyutov, Preben Buchhave, Tatiana Kukhtareva, K. Sayano, Partha P. Banerjee

*Partha Banerjee*

We have developed a compact closed-form solution of the band transport model for high-contrast gratings in photogalvanic crystals. Our solution predicts the effect of the photoconductivity and the electric field grating enhancement due to the photogalvanic effect. We predict a pronounced dependence of the steady-state photogalvanic current on the contrast of the interference pattern and an increase of holographic storage time due to the enhancement of the photoconductivity grating contrast. In the high contrast limit and a large photogalvanic effect the refractive index grating will be shifted from the position of the intensity modulation pattern, contrary to the usually adopted ...

Simulation Of Two-Dimensional Nonlinear Envelope Pulse Dynamics By A Two-Step Spatiotemporal Angular Spectrum Method, 2016 University of Iowa

#### Simulation Of Two-Dimensional Nonlinear Envelope Pulse Dynamics By A Two-Step Spatiotemporal Angular Spectrum Method, H. K. Sim, Adrianus Korpel, Karl E. Lonngren, Partha P. Banerjee

*Partha Banerjee*

We present an extension of our previous nonlinear beam-simulation method to the propagation and interaction of pulse envelopes. The extra time dimension is applied in the context of a dispersive nonlinear medium that is described by a Klein–Gordon equation with an added cubically nonlinear, self-focusing term. Pulse propagation in this medium is modeled as the evolution of a spatiotemporal spectrum—i.e., the frequency-dependent angular spectrum of the pulse envelope—traversing a sequence of self-induced, thin, weak phase filters. Preliminary simulation experiments show agreement with known behavior in the absence of nonlinearity, confirm the existence of an (apparently unstable ...

Time Dynamics Of Self-Pumped Reflection Gratings In A Photorefractive Polymer, 2016 University of Dayton

#### Time Dynamics Of Self-Pumped Reflection Gratings In A Photorefractive Polymer, Partha P. Banerjee, S. H. Buller, C. M. Liebig, S. A. Basun, Gary Cook, Dean R. Evans, Pierre-Alexandre Blanche, J. Thomas, Cory W. Christenson, N. Peyghambarian

*Partha Banerjee*

The time dynamics of self-pumped reflection gratings in a commonly used photorefractive polymer PDCST:PVK:ECZ-BBP:C60 with no additional electron sources or traps is investigated. While holes are normally the mobile charges and responsible for grating formation, our experimental observations, analyzed using multi-exponential fitting curves, show evidence of electrons in addition to holes as charge carriers, particularly above an applied field of 40 V/μm.

The dependence of effective carrier mobilities on the applied electric field, deduced from experimental results, show stronger field dependence of electron mobility at high electric fields. At an applied field of 70 V/μm ...

Theoretical And Experimental Studies Of Propagation Of Beams Through A Finite Sample Of A Cubically Nonlinear Material, 2016 University of Dayton

#### Theoretical And Experimental Studies Of Propagation Of Beams Through A Finite Sample Of A Cubically Nonlinear Material, Partha P. Banerjee, Raj M. Misra, M. Maghraoui

*Partha Banerjee*

Propagation of an externally focused or defocused Gaussian beam in a cubically nonlinear material is studied analytically and experimentally. The theoretical analysis is applied to determine the sign and magnitude of *n*2 for a material by means of a single-beam experiment with a finite nonlinear sample within which propagational diffraction cannot be neglected. Experimental results for a solution of chlorophyll in ethanol are reported. Based on available theory, an average *n*2 can be defined for a nonlinearity of thermal origin, and this value is found to be in good agreement with experimental results. Finally, the theoretical analysis and ...

Volume Holographic Recording And Readout For 90-Deg Geometry, 2016 University of Dayton

#### Volume Holographic Recording And Readout For 90-Deg Geometry, Partha P. Banerjee, Monish Ranjan Chatterjee, Nickolai Kukhtarev, Tatiana Kukhtareva

*Partha Banerjee*

When a prerecorded cross-beam hologram is reconstructed (so-called edge-lit readout) with a uniform plane wave and a point source, the resulting exact solutions reveal Bessel-function-type diffracted beam profiles, which are fundamentally modified under weak propagational diffraction. The case of a profiled beam readout with propagational diffraction may be analyzed using a transfer function approach based on 2-D Laplace transforms. In a second series of investigations, dynamic readout from a cross-beam volume hologram recorded with two orthogonal uniform plane waves is considered for various dependences of the refractive index modulation with intensity. Typically, refractive index profiles that are proportional to the ...

Volume Holographic Optical Elements, 2016 National Central University

#### Volume Holographic Optical Elements, Ching-Cherng Sun, Partha P. Banerjee

*Partha Banerjee*

The final two papers are concerned with the analysis of novel holograms. Banerjee et al. investigate holographic recording and reconstruction for edge-lit holograms recorded in a 90-degree geometry. Various cases of recording and readout that incorporate propagational diffraction have been modeled. It is shown that the 90-degree geometry can result in beam shaping, as evidenced through preliminary experimental results with photorefractive lithium niobate. Nguyen et al. propose a new approach for designing computer-generated holograms. An artificial neural network is used to initiate the genetic algorithm so that the high computation cost of genetic algorithms for synthesizing holograms is significantly reduced ...

Rotation-Invariant Synthetic Discriminant Function Filter For Pattern Recognition, 2016 University of South Alabama

#### Rotation-Invariant Synthetic Discriminant Function Filter For Pattern Recognition, Vahid R. Riasati, Partha P. Banerjee, Mustafa A. G. Abushagur, Kenneth B. Howell

*Partha Banerjee*

The ring synthetic discriminant function (RSDF) filter for rotation-invariant response is discussed for pattern recognition. This method uses one half of a slice of the Fourier transform of the object to generate the transfer function of the filter. This is accomplished by rotating the one half of a slice in the Fourier domain through 2π rad about the zero-frequency point of the Fourier plane. This filter has the advantage of always matching at least one half of a slice of the Fourier transform of any rotation of the image. An analytical discussion of the filter construction and correlation results are ...

On A Simple Derivation Of The Fresnel Diffraction Formula And A Transfer Function Approach To Wave Propagation, 2016 University of Dayton

#### On A Simple Derivation Of The Fresnel Diffraction Formula And A Transfer Function Approach To Wave Propagation, Partha P. Banerjee, Ting-Chung Poon

*Partha Banerjee*

The Fresnel diffraction formula is straightforwardly obtained by solving a partial differential equation (PDE) for envelope propagation using Fourier transform techniques. The PDE, in turn, can be derived from the dispersion relation of a linear medium by employing a simple operator formalism. The transfer function and impulse response of propagation follows as a spin‐off and is used to solve illustrative problems. Huygens’ principle is visualized as a consequence of the convolution property of linear systems.

Notch Spatial Filtering With An Acousto-Optic Modulator, 2016 University of Dayton

#### Notch Spatial Filtering With An Acousto-Optic Modulator, Partha P. Banerjee, Dongqing Cao, Ting-Chung Poon

*Partha Banerjee*

The role of acousto-optic (AO) modulators in programmable real-time image processing has recently been demonstrated. For fully investigating the image-processing capabilities of the AO modulator, general techniques to derive spatial transfer functions are needed for a variety of physical situations. We develop a technique to determine the spatial transfer functions numerically for various cases of beam incidence on an AO modulator. Normal incidence and incidence at twice the Bragg angle are investigated as examples for which double-sided and single-sided notch spatial filtering, respectively, are achieved. The observed spatial-filtering characteristics are reconciled with simple intuitive physical arguments.

Nonlinear Transverse Effects In Second-Harmonic Generation, 2016 Syracuse University

#### Nonlinear Transverse Effects In Second-Harmonic Generation, Pawel Pliszka, Partha P. Banerjee

*Partha Banerjee*

We study a three-dimensional model of interaction of fundamental-frequency and second-harmonic beams in a quadratically nonlinear medium. Numerical simulations of the three-dimensional propagation problem in the presence of diffraction and anisotropy are performed under the paraxial approximation. The role of the transverse effects in various regimes is investigated. We demonstrate the effect of phase modulation and an induced nonlinear focusing during the interaction of the fundamental frequency with the generated second harmonic.

Laser Beam Profile Deformation Effect During Bragg Acousto-Optic Interaction: A Non-Paraxial Approximation, 2016 National Taiwan University of Science and Technology

#### Laser Beam Profile Deformation Effect During Bragg Acousto-Optic Interaction: A Non-Paraxial Approximation, Ray S. Huang, Chen-Wen Tarn, Partha P. Banerjee, Doungchin Cao

*Partha Banerjee*

It is commonly known that the spatial profiles of the diffracted light beams during Bragg acousto-optic interaction are distorted due to the Bragg angle selection mechanism. All the conventional studies on this effect use the paraxial approximation. But this approximation should be amended when the incident angle of the light is large enough that the diffracted light waves do not propagate closely along the optic axis of the acousto-optic diffraction system. By using a spatial Fourier transform approach, we rigorously study the light beam profile deformation effect of the diffracted light during the Bragg acousto-optic interaction beyond the paraxial approximation ...

Modeling And Characterization Of Adaptive Lanthanum-Modified Lead Zirconate Titanate (Plzt) Microlenses, 2016 University of Dayton

#### Modeling And Characterization Of Adaptive Lanthanum-Modified Lead Zirconate Titanate (Plzt) Microlenses, Yasser A. Abdelaziez, Partha P. Banerjee

*Partha Banerjee*

We report the modeling and characterization of adaptive voltage controlled electro-optic microlenses. First, we utilize finite element analysis (FEA) to simulate the induced electro-optic effect in lanthanum-modified lead zirconate titanate (PLZT). FEA simulation provides microlens parameters such as phase and focal length. A simple z-scan method is developed to fully characterize the adaptive voltage controlled linear lens. Experimental z-scan results are shown to match the theoretical predictions from FEA.

Multiwave Coupling In A High-Gain Photorefractive Polymer, 2016 Osaka City University

#### Multiwave Coupling In A High-Gain Photorefractive Polymer, Kenji Matsushita, Partha P. Banerjee, S. Ozaki, Daisuke Miyazaki

*Partha Banerjee*

The characteristics of a new high-gain photorefractive polymer composite with a PNP chromophore are investigated. Competition between beam fanning and two-wave coupling (TWC) is predicted and verified experimentally. The intensity dependence of TWC gain is studied. Higher diffraction order and forward phase conjugation in a TWC geometry are observed and explained.

Linear And Nonlinear Propagation In Negative Index Materials, 2016 University of Dayton

#### Linear And Nonlinear Propagation In Negative Index Materials, Partha P. Banerjee, George Nehmetallah

*Partha Banerjee*

We analyze linear propagation in negative index materials by starting from a dispersion relation and by deriving the underlying partial differential equation. Transfer functions for propagation are derived in temporal and spatial frequency domains for unidirectional baseband and modulated pulse propagation, as well as for beam propagation. Gaussian beam propagation is analyzed and reconciled with the ray transfer matrix approach as applied to propagation in negative index materials. Nonlinear extensions of the linear partial differential equation are made by incorporating quadratic and cubic terms, and baseband and envelope solitary wave solutions are determined. The conditions for envelope solitary wave solutions ...

Interaction Of Profiled Light With Contrapropagating Acoustic Waves: Fourier Transform Approach, 2016 University of Dayton

#### Interaction Of Profiled Light With Contrapropagating Acoustic Waves: Fourier Transform Approach, Partha P. Banerjee, Chen-Wen Tarn, Jaw-Jueh Liu

*Partha Banerjee*

A straightforward Fourier-transform approach is employed to investigate acousto-optic interaction between an input optical beam with arbitrary profile and contrapropagating cw sound in the Bragg regime. The process can be analyzed in terms of the simultaneous scattering of light by the two sound waves in the interaction region. Analytic expressions for the equivalent transfer functions are obtained and the scattered light profiles are plotted.

Broadband Dynamic, Holographically Self-Recorded, And Static Hexagonal Scattering Patterns In Photorefractive Knbo3:Fe, 2016 Alabama A & M University

#### Broadband Dynamic, Holographically Self-Recorded, And Static Hexagonal Scattering Patterns In Photorefractive Knbo3:Fe, Nickolai Kukhtarev, Tatiana V. Kukhtareva, John Caulfield, Partha P. Banerjee, Hsueh-Ling Yu, Lambertus Hesselink

*Partha Banerjee*

We have observed and explained three types of hexagon pattern formation in photo refractive crystal KNb03:Fe. These are:

- Dynamic (laser induced)
- Semipermanent (holographically stored)
- Permanent (induced by a static domain grid) over a wide wavelength range