Signal beam

About: Signal beam is a research topic. Over the lifetime, 1881 publications have been published within this topic receiving 20717 citations.

Nonlinear Negative Refraction by Difference Frequency Generation

Abstract: Negative refraction has attracted much interest for its promising capability in imaging applications. Such an effect can be implemented by negative index meta-materials, however, which are usually accompanied by high loss and demanding fabrication processes. Recently, alternative nonlinear approaches like phase conjugation and four wave mixing have shown advantages of low-loss and easy-to-implement, but associated problems like narrow accepting angles can still halt their practical applications. Here we demonstrate theoretically and experimentally a new scheme to realize negative refraction by nonlinear difference frequency generation with wide tunability, where a thin BBO slice serves as a negative refraction layer bending the input signal beam to the idler beam at a negative angle. Furthermore, we realize optical focusing effect using such nonlinear negative refraction, which may enable many potential applications in imaging science.

Pickup module with coating layer

Abstract: A pickup module comprises a plurality of optical components along an optical path, wherein at least two of the optical components are provided with coating layers to change a polarization of a light beam and collectively circularly polarize the light beam. The circularly-polarized beam is projected on an optical storage medium and converted to a signal beam received by an optical detector. A quarter wavelength plate (QWP) or the other phase retarded plate for required purpose (½λ, ¼λ, ⅛λ . . . ) is not included in the optical component set.

Polarisation singularities in the electric field at a sum-frequency generated by two collinear elliptically polarised Gaussian beams in the bulk of a nonlinear gyrotropic medium

Abstract: Polarisation singularities in the electric field at a sum-frequency generated in the bulk of an isotropic gyrotropic medium with a quadratic nonlinearity are predicted to appear in the case of the collinear interaction of two uniformly elliptically polarised Gaussian beams The parameters of the fundamental waves are found, corresponding to the formation of lines with circular and linear polarisations (C- and L-lines) in the cross section of the beam at the sum-frequency as well as to the appearance of the regions in the signal beam where the polarisation state varies smoothly from the left-hand circularly polarised state to the right-hand circularly polarised In this case, the ellipticity degree of the polarisation ellipse takes all possible values, while its orientation remains unchanged

Experiment on PR SEW of SBN crystal

Abstract: Photorefractive surface electromagnetic wave (PR SEW) at the interface between SBN crystal and air based on drift and diffusion mechanism was observed experimentally for the first time. PR SEW can be formed when laser beam was incident at an angle of 55° in proper ratio of signal beam to background beam, and the intensity of PR SEW increases along with the increasing of additional electric field.