Polarimetric properties of asteroids in the near-infrared

<p>We present first results from a polarimetric survey of asteroids in the near-infrared J and H bands (1.25 and 1.65 microns, respectively). This survey has been enabled by the newly commissioned WIRC-Pol instrument on the Palomar 5 m telescope.  WIRC-Pol simultaneously senses the four linear polarization components from the target, while using a half-wave plate to beam swap between them. This setup allows us to obtain bandpass polarimetric accuracies better than 0.1% for our targets.  WIRC-Pol also obtains low resolution spectra of each Stokes component, allowing us to investigate the spectropolarimetric properties of our targets as a function of phase.  We show polarimetric phase curves for objects that have been sampled at multiple phases, our initial spectropolarimetric findings, and discuss the results from modeling these observations. </p>

The Navier–Stokes–Vlasov–Fokker–Planck System as a Scaling Limit of Particles in a Fluid

Convergence of a system of particles, interacting with a fluid, to Navier–Stokes–Vlasov–Fokker–Planck system is studied. The interaction between particles and fluid is described by Stokes drag force. The empirical measure of particles is proved to converge to the Vlasov–Fokker–Planck component of the system and the velocity of the fluid coupled with the particles converges in the uniform topology to the the Navier–Stokes component. A new uniqueness result for the PDE system is added.

Polarizers

Introduction to how to measure polarization and the degree of polarization, The various physical processes used to control polarization including: absorption, reflection, interference, and birefringence. An explaination of the operation of a wire grid and its molecular equivalent, a polaroid plastic are given. Fresnel formula for reflection is used to calculate the Stokes component of the reflected light. A brief introduction to the concept of birefringence is given and the various designs of birefringent prism polarizers are listed with their advantanges and shortcomings. A sample design of a prism polarizer is given. Quarter wave and half wave retarders and their use are discussed. An optional section is devoted to optical activity and the use of chiral measurements in chemistry and drug manufacturing are discussed.

Панорамная спектроскопия спонтанного комбинационного рассеяния для диагностики струйных реагирующих потоков с использованием перестраиваемого фильтра Лио-Эмана

The spatial-density distribution in burning a premixed methane–air swirling turbulent jet has been studied by measuring the intensity of the Stokes branch of spontaneous Raman scattering for vibrational–rotational transitions in nitrogen. An optical system comprising a Nd:YAG laser and the liquid-crystalline Lyot–Ehman tunable filter has been created and tested by measuring the temperature and density fields in a cone-shaped laminar flame. It has been established that the difference of data obtained using the Stokes component of Raman scattering in nitrogen and its ratio to the anti-Stokes component does not exceed 5% in a temperature range from 300 to 1800 K.

Self-pumped SBS effect of high-power super-Gaussian-shaped laser pulses

Most of the high-energy laser systems deliver temporally super-Gaussian-shaped laser pulses. The propagation properties of this kind of pulses in a nonlinear medium are studied in this paper. There is Stokes component in the sideband spectrum of super-Gaussian-shaped pulses, and the frequency difference between the Stokes component and the center frequency is equals to the Brillouin frequency of the nonlinear medium. When the laser is reflected by optical elements in the light path, Stokes component in the reflected light can be amplified by the subsequent part of the laser pulse and excite stimulated Brillouin scattering (self-pumped SBS). The self-pumped SBS is studied theoretically and experimentally, and the experimental results agreed well with the calculated results. The simulation results show that lower-order super-Gaussian-shaped pulses are more suitable for suppressing the self-pumped SBS and of great benefit to the energy delivering of the high-power laser pulses. To the best of our knowledge, this is the first time to experimentally demonstrate the self-pumped SBS of high-power super-Gaussian-shaped laser pulses.