Non-diffracting integer-order and half-integer-order carpet beams obtained by even-type sinusoidal amplitude radial gratings

In this work,we introduce a kind of new structured radial grating,which is named the even-type sinusoidal amplitude radial(ETASR)grating.Based on diffraction theory and the principle of stationary phase,a comprehensive theoretical investigation on the diffraction patterns of ETASR gratings is conducted.Theoretical results show that novel carpet beams with beautiful optical structures and distinctive characteristics have been constructed on the basics of the ETASR grating.Their diffraction patterns are independent of propagation distance,that is,the new carpet beams have diffraction-free propagating characteristics.The non-diffracting carpet beams are divided into two types by beam characteristics:non-diffracting integer-order and half-integer-order carpet beams.Subsequently,we experimentally generate these carpet beams using the ETASR grating.Finally,their particularly interesting optical morphology and features are explored through numerical simulations and experiments.

Composite Sinusoidal Nanograting With Long-Range SERS Effect for Label-Free TNT Detection

A composite one-dimensional （1D） Ag sinusoidal nanograting aiming at label-free surface enhanced Raman scattering （SERS） detection of TNT with robust and reproducible enhancements is discussed. 1D periodic sinusoidal SiO2 grating followed by Ag evaporation is proposed for the creation of reproducible and effective SERS substrate based on surface plasmon polaritons （SPPs）. The optimal structure of 1D sinusoidal nanograting and its long-range SERS effect are analyzed by using the finite difference time domain （FDTD）. Simulation SERS enhancement factor （EF） can be 5 orders of magnitude as possible. This SERS substrate is prepared by the interference photolithography technology, its SERS performance is tested by Rh6G detection experiments, and the actual test EF is about 10. The label-free SERS detection capacity of TNT is demonstrated in the experiment.

Wavefront sensing based on phase contrast theory and coherent optical processing

A novel wavefront sensing method based on phase contrast theory and coherent optical processing is proposed. The wavefront gradient field in the object plane is modulated into intensity distribution in a gang of patterns, making highdensity detection available. By applying the method, we have also designed a wavefront sensor. It consists of a classical coherent optical processing system, a CCD detector array, two pieces of orthogonal composite sinusoidal gratings, and a mechanical structure that can perform real-time linear positioning. The simulation results prove and demonstrate the validity of the method and the sensor in high-precision measurement of the wavefront gradient field.

A correction method of color projection fringes in 3D contour measurement

In the three-dimensional(3D) contour measurement,the phase shift profilometry(PSP) method is the most widely used one.However,the measurement speed of PSP is very low because of the multiple projections.In order to improve the measurement speed,color grating stripes are used for measurement in this paper.During the measurement,only one color sinusoidal fringe is projected on the measured object.Therefore,the measurement speed is greatly improved.Since there is coupling or interference phenomenon between the adjacent color grating stripes,a color correction method is used to improve the measurement results.A method for correcting nonlinear error of measurement system is proposed in this paper,and the sinusoidal property of acquired image after correction is better than that before correction.Experimental results show that with these correction methods,the measurement errors can be reduced.Therefore,it can support a good foundation for the high-precision 3D reconstruction.