Polarization State Of Laser Beam Research Articles

Polarization-Sensitive Patterning of Azopolymer Thin Films Using Multiple Structured Laser Beams

The polarization sensitivity of azopolymers is well known. Therefore, these materials are actively used in many applications of photonics. Recently, the unique possibilities of processing such materials using a structured laser beam were demonstrated, which revealed the key role of the distribution of polarization and the longitudinal component of light in determining the shape of the nano- and microstructures formed on the surfaces of thin azopolymer films. Here, we present numerical and experimental results demonstrating the high polarization sensitivity of thin azopolymer films to the local polarization state of an illuminating structured laser beam consisting of a set of light spots. To form such arrays of spots with a controlled distribution of polarization, different polarization states of laser beams, both homogeneous and locally inhomogeneous, were used. The results obtained show the possibility of implementing a parallel non-uniform patterning of thin azopolymer films depending on the polarization distribution of the illuminating laser beam. We believe that the demonstrated results will not only make it possible to implement the simultaneous detection of local polarization states of complex-shaped light fields but will also be used for the high-performance fabrication of diffractive optical elements and metasurfaces.

Terahertz Radiation Generation by Frequency Mixing of Hermite–Cosh–Gaussian Laser Beams in Density-Modulated Cold Magnetized Plasma

We report a theoretical investigation for extremely bright terahertz (THz) radiation generation by mixing of dichromatic Hermite–Cosh–Gaussian (HChG) laser beams in periodically rippled density plasma in the presence of external dc magnetic field. The magnetic field is applied perpendicular to the direction of propagation and to the polarization states of laser beams. THz field amplitude significantly increases with applied dc magnetic field. Our investigations reveal that frequency resonance shifts with the applied magnetic field. As a result, THz frequency tuning is possible with applied magnetic field. The electron neutral collisions have no effect on resonance condition but THz amplitude and efficiency decreases with increase in frequency of electron neutral collisions. We find that THz field profile strongly depends on laser parameters like Cosh decentred parameter $b$ and order of Hermite function $s$ , and independent of applied magnetic field. Our theoretical investigations predict that GV/m THz field with efficiency ~7% for laser field ~50 GV/m and 80-kG applied dc magnetic field can be obtained for optimized set of laser and plasma parameters.

Laser scattering, optical constants and connection to other material performances (Kerr constant, mobility/diffusion coefficient/electrophoresis and depolarization)

Scattering of optical photons from the view of parallel methods related to absorption, scattering, fluorescence, reflection with inclusion of the polarization states of laser beams from experiment and theory give many possibilities for obtaining indirect data on material, processes, and dynamics. As a method with minimal perturbations, if low power beams are involved, certain type of data is provided. In fundamental dependences of various material properties, many phenomenological and basic laws are covered. Several coupled variables, primarily with the processes of scattering, pointing out further possibilities for linking the obtained theoretical or experimental results were presented. By including simulations, this associates with biological environments / variables for properties equivalent to defined tissues, cells, and characteristics. Along with selected formalisms including Stokes vectors and scattering matrices, a biological cell as an object can be monitored in time and influence of various environments could be predicted. Connecting Kerr’s effect with depolarization and scattering makes the complete description of molecule possible. Angular scattering observation with experimental possibilities gives the fastest practical data. This enables interpretation of E. coli with the application of Stokes vector formalisms. A relatively small number of material constants for many simulation cases could give draft estimation, but the experiment depends on the measuring devices and samples. The necessary symmetries showing the size of the scattering centers are analyzed, with the scattering data for some liquids (known / less known). From measured data, depolarization could be calculated, and with refractive index (molar refraction) connection with Kerr effect/ birefringence for selected solutions and behavior of molecules could be monitored. From the experimental Rayleigh factors, cross section (apparent/ effective) and attenuation coefficients for pure liquids were calculated. An approach for the correct assessment of the measurement uncertainty in the process of calibration of polyethylene samples was used.

Influence of the electron beam emittance on the polarization of a laser-electron x-ray generator

In this paper we analyze the polarization of the X-ray radiation coming from laser--electron X-ray generator (LEXG). We obtain general relations connecting the polarization state of outgoing X-ray radiation to the polarization state of laser beam as well as to the parameters of electron beam. We demonstrate that finite electron beam emittance causes a partial depolarization of initially fully polarized X-ray radiation even when the laser beam is fully polarized. We demonstrate with a number of numerical experiments that finite electron beam emittance can in some cases fundamentally alter the polarization state of X-ray radiation as compared to the polarization state of X-ray radiation scattered by electron beam with a zero emittance. Possible applications of polarized LEXG's radiation are discussed.

基于空间光调制器的光束偏振态控制方法研究

基于空间光调制器的光束偏振态控制方法研究

Direct surface relief formation on As2S3–Se nanomultilayers in dependence on polarization states of recording beams

Direct one step grating relief formation by laser beam on the surface of amorphous chalcogenide nanomultilayers of the composition As2S3–Se was performed. Successive nanolayers on a glass substrate were prepared by thermal vacuum deposition with cyclic motion of substrate. Optical constants were obtained from transmission spectra data in the range of 450–900nm. The dependence of the surface relief formation on nanomultilayers vs. the polarization states of laser beams was studied. The surface gratings with maximum relief depth were recorded under the two linear polarized beams falling on the sample surface at (+45°)–(−45°). Holographic diffraction gratings with the diffraction efficiency ∼28% value in transmission mode at λ=0.65μm were recorded without additional treatment. This fact is explained by the contribution of mass transport whose direction is defined by the electric vector of laser beams. Recorded grating provides high optical quality of the obtained relief with depth of the grooves of about 100nm at the total structure thickness 2500nm.

Radially Polarized and Passively Q-Switched Nd:YAG Laser Under Annular-Shaped Pumping

We reported, for the first time, a radially polarized and passively Q-switched Nd:YAG laser with annular-shaped pumping. The annular intensity profile of the pump light was originated from the mode conversion in a conventional multi-mode fiber under off-focus coupling. Radially polarized pulse from this laser had 3.3 kW peak power, 39 ns duration at 2.5-kHz repetition rate with ~90% degree of polarization. When the laser crystal was slightly tilted, the polarization state of laser beam was switched to azimuthal polarization at high pump power, while remained radial polarization at lower pump power.

Polarization characterization in the focal volume of high numerical aperture objectives

In this paper the polarization states of linearly and radially polarized plane wave and doughnut beams in the focal volume of high numerical aperture objectives are studied. Through manipulating the incident polarization states of laser beams as well as the apodization of an objective and adjusting the numerical aperture of an objective, focal fields dominantly with either one transverse component or one longitudinal component can be generated. Furthermore, tailored polarization distributions with three polarization components of the same strength are also found.