Search results for "birefringence"
showing 10 items of 133 documents
Orientation of polybutadiene chains in a thermoplastic elastomer
1996
The orientation of polybutadiene chains in thermoplastic elastomers based on hydrogen bonding complexes is investigated under uniaxial deformation by two-dimensional small-angle neutron scattering (SANS), deuteron magnetic resonance spectroscopy (2H-NMR), optical birefringence and infrared dichroism spectroscopy (FTIR-D). While SANS probes orientation on the length scale of the radius of gyration,2H-NMR, birefringence and FTIR-D monitor orientation on a segmental scale. The deformation of the elastomer chains appears to be affine on the different length scales.
Long cavity ring fiber mode-locked laser with decreased net value of nonlinear polarization rotation
2019
We investigate a new configuration of a mode-locked fiber laser by using a nonlinear polarization rotation-based design to generate soliton pulses with low repetition rate. Unlike with previously reported configurations, we introduce a Faraday mirror after the first half of the cavity length to counteract the nonlinear polarization rotation effects. The total cavity length is 437 m including a 400-m long twisted SMF-28 fiber. The fiber was twisted to cancel the linear birefringence and to ensure that the polarization ellipticity is not altered as the pulse travels along the fiber. The strict control of polarization yields a stable relation between the polarization state of the pulses propag…
Optical field-induced surface-relief micropatterning of amorphous chalcogenide thin films
2015
The study of direct recording of the surface relief gratings on amorphous chalcogenide thin (2.5 to 5 μm films is presented by three different recording setups. Recording was performed on As2S3 by 532-nm wavelength laser light. Additionally, the evolution of a surface relief in dependence from the recording time and polarization has been investigated in detail and for the first time, the mass transfer process has been explained from the point of view of the photoinduced birefringence. The role of photoinduced plasticity in the formation of surface relief in amorphous chalcogenides during holographic recording has been discussed.
Impact of anionic system modification on the desired properties for CuGa(S1−Se )2 solid solutions
2021
Abstract One of promising directions of the modern solar cells’ development is related to the use of the ternary chalcopyrite crystals (CuInS2, CuGaS2 etc.) and their solid solutions as efficient light absorbing layers. Unfortunately, so far there is no systematic research linking chemical composition to useful properties allowing their optimization to increase the efficiency of solar cells. Therefore, we report the results of the detailed theoretical studies of the structural, electronic, and optical properties for the series of CuGa(S1−xSex)2 solid solutions (x = 0, 0.25, 0.5, 0.75, 1) in the framework of the density functional theory. For this purpose, crystal structures are analyzed wit…
Photoinduced mass transport in azo compounds
2013
The photoinduced changes of optical properties in azobenzene containing compound thin films were studied under influence of polarized and non-polarized 532 nm laser light. Under influence of light azo compounds experience trans-cis isomerisation process, that can be observed in the absorbance spectrum of the sample. If the light is linearly polarized, molecules align perpendicularly to the electric field vector and as a result photoinduced dichroism and birefringence is obtained. If a known lateral polarization modulation of the light beam is present, mass transport of the azobenzene containing compound occurs. By measuring the surface relief with a profilometer the direction of mass transp…
Polymer waveguide couplers based on metal nanoparticle–polymer nanocomposites
2015
In this work Au nanoparticles (AuNPs) are incorporated into poly(methyl methacrylate) (PMMA) waveguides to develop optical couplers that are compatible with planar organic polymer photonics. A method for growing AuNPs (of 10 to 100 nm in size) inside the commercially available Novolak resist is proposed with the intention of tuning the plasmon resonance and the absorption/scattering efficiencies inside the patterned structures. The refractive index of the MNP-Novolak nanocomposite (MNPs: noble metal nanoparticles) is carefully analysed both experimentally and numerically in order to find the appropriate fabrication conditions (filling factor and growth time) to optimize the scattering cross…
Highly Anisotropic Wave Propagation in All-Dielectric Active Waveguides
2018
In this communication, we integrate an active planar waveguide on a birefringent substrate to show experimental evidence of a selective propagation of the spontaneous emission into the propagating. An anisotropic response with significantly-reduced directional excitation along the optic axis as compared with its perpendicular direction is observed. We additionally provide a theoretical modal analysis of the planar microstructure, which is in good agreement with our experimental results.
Programmable color tuning of a multiline laser by means of a twisted nematic liquid crystal display.
2012
An optical system useful to tune in a controlled way the color of a triline argon krypton (Ar–Kr) laser by means of a twisted nematic liquid crystal display (TNLCD) is presented. The optical setup employs a 4f system and two blazed gratings to first separate and then recombine the spectrum of the light beam. The TNLCD is included in the intermediate focal plane operating in the amplitude modulation mode to control the relative transmission of each spectral line. The resulting color is accurately predicted by using a previously developed physical model of the spectral and voltage dependence of the TNLCD birefringence. By simply changing the gray level image addressed to the display, the Ar–K…
Nonlinear frequency conversion in a birefringent microstructured fiber tuned by externally applied hydrostatic pressure.
2013
We studied vector frequency conversion in externally tuned microstructured fibers for applications as a novel, nonlinear fiber-optic sensor. We investigated both experimentally and numerically a possibility of shifting vector and scalar modulation instability gain bands by pressure-induced changes in the linear properties of a microstructured fiber. Our results show that polarization-dependent vector nonlinear processes sensitive to variation of fiber group velocity difference (group birefringence) exhibit a clear advantage for pressure-sensing applications compared with scalar nonlinear processes only sensitive to group velocity dispersion changes. Analytical predictions and numerical simu…
Non-critically phase-matched cascaded THG at 440 nm in KTiOP1−yAsyO4 crystals
1995
Abstract We report the relative nonlinear optical properties of flux-grown KTiOP 1− y As y O 4 crystals ( y =0, y =0.03 and y =0.12). The non-critical phase-matching temperatures along the x -axis for blue generation by type II indirect third harmonic generation from 1318.8 nm and 1320 nm are measured. The phosphorus-arsenic substitution allows a “chemical tuning” of the phase-matching properties, through a birefringence variation, so that non-critical phase-matching at room temperature is possible for the previous interactions. Type II frequency doubling from 1064 nm is briefly considered.