Experimental investigation of light storage of diffraction-free and quasi-diffraction-free beams in hot atomic gas cell

In this article we report on the experimental investigation of light storage for several types of diffractionfree beams(Bessel and Airy beams)and quasi-diffraction-free beams by utilizing electromagnetically induced transparency(EIT)technique in a hot atomic gas cell.The experimental results show that the diffraction-free and quasi-diffraction-free beams have better storage performances when compared with ordinary images possessing similar spatial profiles.Meanwhile,the Bessel beams and the quasidiffraction-free images are able to maintain their spatial profiles with a long storage time while the sidelobes of the Airy beam are gradually depleted with the increment of the storage time.We quantitatively analyze the storage results and give physical explanations behind these phenomena.Furthermore,the self-healing of the retrieved diffraction-free beams is verified,signifying that their characteristics preserve well after storage.

Generation of Mathieu beams using angular pupil modulation

By using an amplitude-type spatial light modulator to load angular spectrum of Mathieu function distribution along a narrow annular pupils, the Durnin’s experimental setup is extended to generate various types of Mathieu beams. As a special type of Mathieu beams, Bessel beams are also generated using this optical setup. Furthermore, the optical morphology of the Mathieu beams family are also presented and analyzed.

Terahertz Bessel Beam Applied to Thickness Measurement of Ellipsometry Methods

This paper introduces a Terahertz (THz) ellipsometer thickness measurement method based on Bessel beams. The ellipsometry method is used to measure the thickness of film in the THz band. And the thickness of film could be measured in the range of hundreds of microns which the measurement of film thickness by ellipsometer is usually only a few hundred nm in visible light. In addition, the photon energy of the THz-wave is very low and has little damage to the film. The THz Bessel beam has the characteristics of self-healing and diffraction-free. It can make the film thickness measurement within the diffraction-free distance, which is conducive to the flexibility of the ellipsometer system. We use a multi-frequency method to measure film with two-dimensional finite different time domain (FDTD) to numerical simulation analysis of light intensity successfully.