Showing posts with label Yanlin Zhao. Show all posts
Showing posts with label Yanlin Zhao. Show all posts

Monday, December 10, 2018

Abstract-Numerical and experimental analysis of Bessel beam properties based on continuous-wave terahertz radiation



Zhihao Xu, Lu Rong, Dayong Wang, Bin Li, Yanlin Zhao, Jie Zhao, Yunxin Wang

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10826/108261C/Numerical-and-experimental-analysis-of-Bessel-beam-properties-based-on/10.1117/12.2501241.short

Terahertz imaging technology has been widely used in various fields. In continuous-wave terahertz imaging system, when the large size object is located at the unfocused position, Bessel beam with non-diffractive properties show its large depth of focus advantage over Gaussian beam. Bessel beam can be generated by the axicon, which has high conversion efficiency. The non-diffraction distance and the main lobe size of the Bessel beam depend on the parameters of the axicon and incident light wavelength. We analyzed that the influence on the axial two-dimensional intensity distribution of a zero-order Bessel beam by changing the axicon parameters and the incident Gaussian beam size. Experimentally, the axicon with different parameters were fabricated using different materials. Then the two-dimensional intensity distribution of the Bessel beam in the axial and transverse direction were recorded and analyzed. The experimental results is basically consistent with the theoretical ones.
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Sunday, December 9, 2018

Abstract-Encapsulated morphology measurement based on continuous-wave terahertz reflective off-axis digital holography


Yanlin Zhao, Dayong Wang, Lu Rong, Yunxin Wang, Jie Zhao, Zhihao Xu

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10826/1082616/Encapsulated-morphology-measurement-based-on-continuous-wave-terahertz-reflective-off/10.1117/12.2501115.short


Terahertz nondestructive testing is an increasingly important technology in recent years. Compared with visible and infrared bands, terahertz wave can easily penetrate common nonpolar and nonmetal materials without ironize the sample because of low energy. Digital holography can reconstruct the quantitative amplitude and phase distributions of the object wavefront. We proposed a continuous-wave terahertz reflective off-axis digital holography to measure the morphology of encapsulated object. An experimental system was built using a 2.52 THz (118.83 μm) far-infrared gas laser 295-FIR and a pyroelectric array detector. The morphology of the metallic bookmark hidden behind the optically opaque materials such as polytetrafluoroethylene and Polypropylene plates were obtained by angular spectrum integral and phase unwrapping algorithm. It proves that THz digital holography is an effective nondestructive testing method.
© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.