WAVE MIXING IN A BULK PHOTOREFRACTIVE MEDIUM: SPATIOTEMPORAL STRUCTURES AND AMPLITUDE EQUATIONS

2001 ◽  
Vol 11 (11) ◽  
pp. 2823-2836
Author(s):  
O. SANDFUCHS ◽  
F. KAISER ◽  
M. R. BELIĆ
Keyword(s):  
Landau Equation ◽  
Beam Propagation Method ◽  
Wave Interaction ◽  
Transverse Dimension ◽  
Wave Mixing ◽  
Transverse Beam ◽  
First Results ◽  
Reflection Gratings ◽  
Bulk Medium ◽  
Characteristic Features

The counterpropagation of two laser beams through wave mixing in nonlinear optics may lead to spatiotemporal structures in the transverse beam profiles. We theoretically investigate the self-organization process of structures that arise in a photorefractive wave-mixing configuration with an external feedback mirror. The characteristic features mediated through the wave interaction in a bulk medium are discussed. Our group developed a beam propagation method that enabled us to perform numerical simulations beyond the first instability threshold. Primary and secondary spatiotemporal patterns, caused by the sluggish temporal response of the crystal in building reflection gratings, are observed. Analytically a Ginzburg–Landau equation for the order parameter and the corresponding longitudinal eigenfunctions of transverse modes, governing the propagation of the structures through the crystal, are derived and compared with our numerical results in one transverse dimension. First results of hexagonal patterns in two transverse dimensions are also presented.

scholarly journals Solar Radar Observations

1980 ◽  
Vol 91 ◽  
pp. 135-138
Author(s):  
A. O. Benz
Keyword(s):  
Specular Reflection ◽  
Beat Frequency ◽  
Langmuir Wave ◽  
Wave Interaction ◽  
Corner Reflector ◽  
The Sun ◽  
Langmuir Waves ◽  
Radar Observations ◽  
Upper Limit ◽  
First Results

Radar observations of the sun have been made extensively at decameter and low meter wavelengths (Eshleman et al., 1960, and James, 1966). Their interpretation by specular reflection on high density structures with “corner reflector” shape is unlikely from the echo spectral broadening and range depth. Gordon's (1973) interpretation of the scattering by a 4 wave interaction between radar and coronal Langmuir waves requires a level of 10−2nKT (thermal energy density) of the Langmuir waves. A radar experiment in microwaves with the 300 m dish in Arecibo*) is described, which was able to test this hypothesis. It was based on the idea of scattering radar waves on Langmuir waves by the much more efficient 3 wave interaction. The echo at the beat frequency of the radar (2380 MHz) and the Langmuir wave (170 −270 MHz) is then to be expected at 2600 MHz. The results, however, show the absence of echos, from which an upper limit of 6.10−4nKT for the level of Langmuir waves is derived. First results will soon be published (Benz and Fitze, 1979).

Beam propagation method for wide-field nonlinear wave mixing microscope

2015 ◽  
Vol 24 (9) ◽  
pp. 094211
Author(s):  
Yong-Gang Lv ◽  
Zi-Heng Ji ◽  
Wen-Tao Yu ◽  
Ke-Bin Shi
Keyword(s):  
Nonlinear Wave ◽  
Beam Propagation Method ◽  
Beam Propagation ◽  
Wide Field ◽  
Wave Mixing ◽  
Nonlinear Wave Mixing

Analysis of Interface Structures by Quantitative High-Resolution Transmission Electron Microscopy

1996 ◽  
Vol 466 ◽  
Author(s):  
O. Kienzle ◽  
M. Exner ◽  
F. Ernst
Keyword(s):  
Visual Inspection ◽  
Minimum Energy ◽  
Accurate Information ◽  
Sensitive Test ◽  
Transmission Electron ◽  
First Results ◽  
Characteristic Features ◽  
Interface Structures ◽  
Model Structures ◽  
Atomistic Structure

ABSTRACTQuantitative evaluation rather than visual inspection of HRTEM images provides objective, reproducible, and very accurate information on the atomistic structure of internal interfaces. This paper explains the method we have developed to analyze the structure of grain boundaries. To demonstrate the power of our approach we present an analysis of the Σ3 (111) grain boundary in SrTiO3. We have determined the coordinates of the atom columns at this interface with a precision of 0.015 nm. Thus, our experimental results provide a sensitive test for physical theories and model structures obtained by computer simulation. First results of computer modeling are presented in this paper. The calculated structure of minimum energy has the same characteristic features as the structure determined by experiment.

Age Variation of Wood Anatomical Characteristics in Larix cajanderi Tree

2017 ◽  
Vol 2 (1) ◽  
pp. 1-12
Author(s):  
Nadezhda I. Blokhina ◽  
Olesya V. Bondarenko ◽  
Sergey V. Osipov
Keyword(s):  
Anatomical Study ◽  
Growth Rings ◽  
Anatomical Characteristics ◽  
Stem Wood ◽  
First Results ◽  
Age Variation ◽  
Anatomical Characters ◽  
Larix Cajanderi ◽  
Characteristic Features ◽  
First Time

The paper is the first results of the study of age variation of wood anatomy in Larix cajanderi Mayr (Pinaceae). The anatomical study was made from one L. cajanderi tree grown in the optimal habitat for L. cajanderi within areal of this species. Age variability of anatomical characteristics in the direction from pith to bark and along the height of stem is described in detail. Mature wood in L. cajanderi is formed in the base of stem and at breast height in the growth rings numbers 31~40 inclusively, and in the middle of stem in the growth rings numbers 41~50 inclusively. Characteristic features of mature stem wood were not found near the top of tree. Maximal parameters of anatomical characters usually occur in the base of stem. Age variation of wood anatomical characteristics in L. cajanderi tree was obtained for the first time.

scholarly journals Best Fitting Methods for The Mud Profile Equations

2020 ◽  
Vol 6 (1) ◽  
pp. 135
Author(s):  
A Perwira Mulia Tarigan ◽  
Hasanul Arifin Purba
Keyword(s):  
Wave Interaction ◽  
Least Square ◽  
Eastern Coast ◽  
Observation Data ◽  
Profile Data ◽  
Shoreline Stabilization ◽  
Wave Energy Dissipation ◽  
Profile Equation ◽  
Best Fitting ◽  
Characteristic Features

In order to understand the dynamics of shoreline changes due to natural and anthropogenic causes, it is imperative for a coastal manager to comprehend the shore profile characteristics which are dependent on the sediment-wave interaction and can be depicted in a profile equation. Moreover, it is possible to derive the power form for the profile equation of a sandy coast based on the argument of wave energy dissipation per unit bed area and unit time. By using this same argument and considering the phenomenon that the main cause of wave damping over a muddy coast is due to energy absorption by the soft mud bottom, the mud profile equation can also be formulated. The aim of this study was to observe the mud profile equation geometry using best fitting method and to compare the characteristic features of the mud profiles using the field observation data. Shore profile data were measured from the muddy coast of Pantai Cermin in the eastern coast of North Sumatera Province. The data obtained were fitted to both the sand and mud profile equations. The procedures and results of the two best fitting methods, the nonlinear regression and the least square based trial and error search, were exhibited and compared. Several noteworthy features of the mud profile equation were found to be the same with the sand profile equation in describing the profile data. In order to provide a better profile and shoreline stabilization, it is recommended to use more complete observation data and good knowledge of shore profile by the coastal manager.

TEMPORAL AND SPECTRAL ANALYSIS FOR MID-INFRARED FOUR-WAVE MIXING IN QUANTUM INTERSUBBAND STRUCTURE

2013 ◽  
Vol 27 (21) ◽  
pp. 1350149
Author(s):  
BAKTASH HEKMAT ◽  
VAHID AHMADI ◽  
ELHAM DARABI
Keyword(s):  
Beam Propagation Method ◽  
Output Pulse ◽  
Four Wave Mixing ◽  
Wave Mixing ◽  
Third Order ◽  
Nonlinear Optical Susceptibility ◽  
Initial Shape ◽  
Mid Infrared ◽  
Pump And Probe ◽  
Infrared Spectral

We design a quantum cascade (QC) intersubband structure for four-wave mixing (FWM) generation from In 0.53 Ga 0.47 As / In 0.52 Al 0.48 As in the mid-infrared spectral region which can be described by third-order nonlinear optical susceptibility. In this structure, increasing FWM is accomplished by band engineering which modify energy of subbands. To analyze FWM characteristics in a QC structure, the evolution in time and spectral domain of pump and probe input optical pulses with different frequencies during propagation is calculated and simulated by using finite-difference beam propagation method. Central frequencies of pump and probe pulses which are used for driving the amplifier are 37.97 THz and 32.61 THz, respectively. Third order susceptibility responsible for FWM resonance nonlinearity of the structure is enhanced by two orders of magnitude. As power of input pulses rises, the value of the FWM output signal increases but the pulse loses its initial shape. Gain saturation and dispersion play a major role in shaping the output pulse. Results reveal that the FWM optical pulse characteristics are highly sensitive to the pulse power and QC parameters in the time and frequency domains.

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