The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
S.B. Lang - One of the best experts on this subject based on the ideXlab platform.
-
Comparison of techniques for solving the Laser Intensity Modulation Method (LIMM) equation
Journal of Electroceramics, 2008Co-Authors: S.B. Lang, Enis TuncerAbstract:The Laser Intensity Modulation Method (LIMM) is a technique for the determination of polarization and/or space charge profiles in the thickness direction of ceramic and polymeric samples. The experimental data are analyzed by means of a Fredholm integral equation of the first kind. This equation admits to multiple and very different solutions. A number of techniques have been developed in order to obtain the most physically reasonable profile. Several techniques based on the regularization method have been proposed. A recent version, polynomial regularization, was developed by Lang. A completely different approach is the Monte Carlo method of Tuncer and Lang. Several sets of both simulated and experimental data are analyzed by the two methods in this paper. Conclusions concerning speed and accuracy are presented. © 2007 Springer Science+Business Media, LLC.
-
Kramers-Kronig relations in Laser Intensity modulation method
Physical Review B - Condensed Matter and Materials Physics, 2006Co-Authors: Enis Tuncer, S.B. LangAbstract:In this short paper, the Kramers-Kronig relations for the Laser Intensity modulation method (LIMM) are presented to check the self-consistency of experimentally obtained complex current densities. The numerical procedure yields well defined, precise estimates for the real and the imaginary parts of the LIMM current density calculated from its imaginary and real parts, respectively. The procedure also determines an accurate high frequency real current value which appears to be an intrinsic material parameter similar to that of the dielectric permittivity at optical frequencies. Note that the problem considered here couples two different material properties, thermal and electrical; consequently, the validity of the Kramers-Kronig relation indicates that the problem is invariant and linear. © 2006 The American Physical Society.
R Abbott - One of the best experts on this subject based on the ideXlab platform.
-
solid state Laser Intensity stabilization at the 10 8 level
Optics Letters, 2004Co-Authors: J G Rollins, D J Ottaway, M E Zucker, R Weiss, R AbbottAbstract:A high-power, low-noise photodetector, in conjunction with a current shunt actuator, is used in an ac-coupled servo to stabilize the Intensity of a 10^-W cw Nd:YAG Laser. A relative Intensity noise of 1×10^-8 Hz^-1/2 at 10 Hz is achieved.
Enis Tuncer - One of the best experts on this subject based on the ideXlab platform.
-
Comparison of techniques for solving the Laser Intensity Modulation Method (LIMM) equation
Journal of Electroceramics, 2008Co-Authors: S.B. Lang, Enis TuncerAbstract:The Laser Intensity Modulation Method (LIMM) is a technique for the determination of polarization and/or space charge profiles in the thickness direction of ceramic and polymeric samples. The experimental data are analyzed by means of a Fredholm integral equation of the first kind. This equation admits to multiple and very different solutions. A number of techniques have been developed in order to obtain the most physically reasonable profile. Several techniques based on the regularization method have been proposed. A recent version, polynomial regularization, was developed by Lang. A completely different approach is the Monte Carlo method of Tuncer and Lang. Several sets of both simulated and experimental data are analyzed by the two methods in this paper. Conclusions concerning speed and accuracy are presented. © 2007 Springer Science+Business Media, LLC.
-
Kramers-Kronig relations in Laser Intensity modulation method
Physical Review B - Condensed Matter and Materials Physics, 2006Co-Authors: Enis Tuncer, S.B. LangAbstract:In this short paper, the Kramers-Kronig relations for the Laser Intensity modulation method (LIMM) are presented to check the self-consistency of experimentally obtained complex current densities. The numerical procedure yields well defined, precise estimates for the real and the imaginary parts of the LIMM current density calculated from its imaginary and real parts, respectively. The procedure also determines an accurate high frequency real current value which appears to be an intrinsic material parameter similar to that of the dielectric permittivity at optical frequencies. Note that the problem considered here couples two different material properties, thermal and electrical; consequently, the validity of the Kramers-Kronig relation indicates that the problem is invariant and linear. © 2006 The American Physical Society.
Sidney B. Lang - One of the best experts on this subject based on the ideXlab platform.
-
Fredholm integral equation of the Laser Intensity Modulation Method (LIMM): Solution with the polynomial regularization and L-curve methods
Frontiers of Ferroelectricity: A Special Issue of the Journal of Materials Science, 2007Co-Authors: Sidney B. LangAbstract:The Laser Intensity Modulation Method (LIMM) is widely used for the determination of the spatial distribution of polarization in polar ceramics and polymers, and space charge in non-polar polymers. The analysis of experimental data requires a solution of a Fredholm integral equation of the 1st kind. This is an ill-posed problem that has multiple and very different solutions. One of the more frequently used methods of solution is based upon Tikhonov regularization. A new method, the Polynomial Regularization Method (PRM), was developed for solving the LIMM equation with an 8th degree polynomial using smoothing to achieve a stable and optimal solution. An algorithm based upon the L-curve method (LCM) was used for the prediction of the best regularization parameter. LIMM data were simulated for an arbitrary polarization distribution and were analyzed using PRM and LCM. The calculated distribution function was in good agreement with the simulated polarization distribution. Experimental polarization distributions in a poorly poled sample of polyvinylidene fluoride (PVDF) and in a LiNbO3 bimorph, and space charge in polyethylene were analyzed. The new techniques were applied to the analysis of 3-dimensional polarization distributions.
-
Thermal diffusivity by Laser Intensity modulation method (LIMM-TD): A novel technique for the determination of thermal diffusivities and conductivities and its application to porous PZT and silica samples
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, 2007Co-Authors: Sidney B. Lang, Supasarote Muensit, Xiaoqing Wu, Erling Ringgaard, Jason C. Lashley, Yuen Wah WongAbstract:A modification of a technique for the measurement of the thermal diffusivity of thin solid materials is presented. The technique is called Thermal Diffusivity by Laser Intensity Modulation Method (LIMM-TD). It is based on the measurement of the phase retardation of a thermal wave passing through the test material by means of a lead-zirconate-titanate ceramic (PZT) pyroelectric detector. It is not necessary to know either the pyroelectric coefficient of the detector or the Intensity of the Laser beam. The method was tested on quartz samples to verify its accuracy. It was then applied to the study of several sets of ceramic samples with porosities of 20, 25, and 30%. One sample set was poled and the pores were partially filled with the fluid used during poling. A second set was not poled. The poled porous samples had thermal conductivities intermediate between that of a commercial dense sample and those of unpoled materials. Thermal diffusivities and conductivities were also measured on micron-thickness porous silica samples. The experimental results were compared with calculations using several composite mixing theories.
-
Laser Intensity modulation method (LIMM): review of the fundamentals and a new method for data analysis
Dielectrics and Electrical Insulation IEEE Transactions on, 2004Co-Authors: Sidney B. LangAbstract:The Laser Intensity modulation method (LIMM) is widely used for the determination of the spatial distribution of polarization in ceramics, single crystals and polymers. A brief history of the origin and development of LIMM during the past 20 years is presented. The experimental technique and the derivation of the LIMM equation are described. The data analysis requires the numerical solution of a Fredholm integral equation of the 1st kind. This is an illposed problem that has multiple and very different solutions. In this paper, a new technique is proposed that gives the polarization distribution in the form of a special 8th-degree polynomial. Both simulated and experimental data are analyzed with the new technique.
-
Laser Intensity modulation method (limm): Experimental techniques, theory and solution of the integral equation
Ferroelectrics, 1991Co-Authors: Sidney B. LangAbstract:The Laser Intensity Modulation Method (LIMM) was developed for the determination of the spatial\ndistribution of polarization or space charge through the thickness of a dielectric sample. It has been\nused in measurements on a number of ferroelectric ceramics and polymers, single crystals and pyroelectric glass-ceramics. Its applications have included poling studies, determination of crystallite orientation in glass-ceramics and influence of surface treatments on polarization of ceramics. The experimental technique and the theory are reviewed, and modifications for increase of accuracy are discussed. A major difficulty in the analysis of LIMM measurements is the necessity of solving a Fredholm integral equation of the 1st kind using experimental data. This is an ill-posed problem which can inherently yield a number of solutions, each of which satisfies the measured data to within experimental accuracy. A technique was developed for solving this class of equations by a modification of the constrained regularization method. The method was verified by experimental measurements on a lead-zirconatetitanate ceramic (PZT), polyvinylidene fluoride (PVF,), a glass-ceramic and multilayer samples composed of two or three sheets of PVF2, poled in either a positive or a negative direction or unpoled.
J G Rollins - One of the best experts on this subject based on the ideXlab platform.
-
solid state Laser Intensity stabilization at the 10 8 level
Optics Letters, 2004Co-Authors: J G Rollins, D J Ottaway, M E Zucker, R Weiss, R AbbottAbstract:A high-power, low-noise photodetector, in conjunction with a current shunt actuator, is used in an ac-coupled servo to stabilize the Intensity of a 10^-W cw Nd:YAG Laser. A relative Intensity noise of 1×10^-8 Hz^-1/2 at 10 Hz is achieved.
