A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of f...A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing （CS） and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme, only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.展开更多
We give an analysis of the frequency distribution trends in the four lowest bands of two-dimensional square lattices formed by holographic lithography （HL） and in the lattices of the same kind but with regular diele...We give an analysis of the frequency distribution trends in the four lowest bands of two-dimensional square lattices formed by holographic lithography （HL） and in the lattices of the same kind but with regular dielectric columns with increasing filling ratios, and then present a comparative study on the left-handed properties in these two kinds of structures using plane wave expansion method and finite-difference time-domain （FDTD） simulations. The results show that the left-handed properties are more likely to exist in structures with large high-epsilon filling ratios or in a connected lattice.展开更多
A new ternary photopolymer system is used in fabricating photonic crystals （PhCs） with controlled defects by combination of single-photon and two-photon photopolymerization. The former process can produce PhCs in on...A new ternary photopolymer system is used in fabricating photonic crystals （PhCs） with controlled defects by combination of single-photon and two-photon photopolymerization. The former process can produce PhCs in one-step recording with a low-power （tens mW） continuous-wave laser at 532nm, while the latter can create desired defects. The preparation of the material, the optical setup and the preliminary experimental results are given. Compared with other methods, this approach is much more accessible and convenient for use of visible light and has advantages of making PhCs in a large scale quickly and economicaJly and introducing any defects exactly, especially for three-dimensional structures.展开更多
A new structure based on a semi-circular photonic crystal is proposed to achieve asymmetric light propagation. The semi-circular photonic crystal structure proposed in this paper is a deformation of a two-dimensional ...A new structure based on a semi-circular photonic crystal is proposed to achieve asymmetric light propagation. The semi-circular photonic crystal structure proposed in this paper is a deformation of a two-dimensional conventional square photonic crystal. Through the directional bandgap of the semi-circular photonic crystal, the light from one direction can transfer to the other side, but the light from the opposite direction cannot. A high contrast ratio is obtained by designing the constitutive parameters of the photonic crystal and choosing the suitable light frequency. This structure promises a significant potential in optical integration and other areas.展开更多
The negative refraction and imaging effects in photonic crystals can be used to solve diffraction limit problem in near-field optics.Improving transmission efficiency and image resolution is a critical work for negati...The negative refraction and imaging effects in photonic crystals can be used to solve diffraction limit problem in near-field optics.Improving transmission efficiency and image resolution is a critical work for negative refraction imaging.We theoretically investigate the band structures,equi-frequency surfaces,electromagnetic wave propagation,and the image intensity distributions in a two-dimensional hexagonal photonic crystal consisting of hollow components.It is found that,in contrast to a hexagonal photonic crystal consisting of solid dielectric cylinders of the same radius,photonic crystals with hollow components can be used to optimize the all-angle negative refraction.Numerical simulations show that the transmission efficiency and resolution of image can be enhanced by changing the radii of the hollow air rods.展开更多
A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is proposed.The phase distribution of a standard phase object and the least-square method are used to ...A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is proposed.The phase distribution of a standard phase object and the least-square method are used to extract phase shifts over a wide range from 0 to𝜌π.Consequently,the tested object wave can be further reconstructed with the extracted phase shifts.It is accurate and applicable for GPSI of any frame number𝑂(N𝑂≥2).Computer simulation has verified its feasibility and validity.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61775121,61307003,61405122,and 11574311)Key R&D Program of Shandong Province,China(Grant No.2018GGX101002)+1 种基金the Natural Science Foundation of Shandong Province,China(Grant No.R2016FM03)the Fundamental Research Funds of Shandong University,China(Grant No.2015GN031)
文摘A multiple-image encryption method based on two-step phase-shifting interferometry （PSI） and spatial multiplexing of a smooth compressed signal is proposed. In the encoding and encryption process, with the help of four index matrices to store original pixel positions, all the pixels of four secret images are firstly reordered in an ascending order; then, the four reordered images are transformed by five-order Haar wavelet transform and performed sparseness operation. After Arnold transform and pixels sampling operation, one combined image can be grouped with the aid of compressive sensing （CS） and spatial multiplexing techniques. Finally, putting the combined image at the input plane of the PSI encryption scheme, only two interferograms ciphertexts can be obtained. During the decoding and decryption, utilizing all the secret key groups and index matrices keys, all the original secret images can be successfully decrypted by a wave-front retrieval algorithm of two-step PSI, spatial de-multiplexing, inverse Arnold transform, inverse discrete wavelet transform, and pixels reordering operation.
基金Supported by the National Science Foundation of China under Grant Nos 60477005, 50173015, 60377041 and 60677026, and the National Science Foundation of Shandong Province （Y2006A09）.
文摘We give an analysis of the frequency distribution trends in the four lowest bands of two-dimensional square lattices formed by holographic lithography （HL） and in the lattices of the same kind but with regular dielectric columns with increasing filling ratios, and then present a comparative study on the left-handed properties in these two kinds of structures using plane wave expansion method and finite-difference time-domain （FDTD） simulations. The results show that the left-handed properties are more likely to exist in structures with large high-epsilon filling ratios or in a connected lattice.
基金Supported by the National Basic Research Programme of China under Grant No 2004CB719803. NSFC/RGC （50218001）. the National Natural Science Foundation of China under Grant Nos 60477005. 50173015, 60377041, and 60677026, and the Natural Science Foundation of Shandong Province （Y2006A09）.
文摘A new ternary photopolymer system is used in fabricating photonic crystals （PhCs） with controlled defects by combination of single-photon and two-photon photopolymerization. The former process can produce PhCs in one-step recording with a low-power （tens mW） continuous-wave laser at 532nm, while the latter can create desired defects. The preparation of the material, the optical setup and the preliminary experimental results are given. Compared with other methods, this approach is much more accessible and convenient for use of visible light and has advantages of making PhCs in a large scale quickly and economicaJly and introducing any defects exactly, especially for three-dimensional structures.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.60907005,10804063,and 51102148)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2011FQ011 and ZR2010AM025)+3 种基金the Natural Science and Technology Program of Shandong Province,China(Grant No.2011GGH20119)the Research Award Fund for Outstanding Young Scientists of Shandong Province,China(Grant No.BS2011DX023)the Science&Technology Bureau of Shenzhen City,China(Grant No.0014632063100426032)the Independent Innovation Foundation of Shandong University,China(Grant No.2010TB019)
文摘A new structure based on a semi-circular photonic crystal is proposed to achieve asymmetric light propagation. The semi-circular photonic crystal structure proposed in this paper is a deformation of a two-dimensional conventional square photonic crystal. Through the directional bandgap of the semi-circular photonic crystal, the light from one direction can transfer to the other side, but the light from the opposite direction cannot. A high contrast ratio is obtained by designing the constitutive parameters of the photonic crystal and choosing the suitable light frequency. This structure promises a significant potential in optical integration and other areas.
基金the National Natural Science Foundation of China under Grant Nos 60907005,10804063 and 51102148the National Natural Science Foundation of Shandong Province under Grant Nos ZR2011FQ011 and ZR2010AM025+3 种基金the National Science and Technology Program of Shandong Province under Grant No 2011GGH20119the Research Award Fund for Outstanding Young Scientists of Shandong Province under Grant No BS2011DX023the Science&Technology Bureau of Shenzhen under Grant No 0014632063100426032the Independent Innovation Foundation of Shandong University under Grant No 2010TB019.
文摘The negative refraction and imaging effects in photonic crystals can be used to solve diffraction limit problem in near-field optics.Improving transmission efficiency and image resolution is a critical work for negative refraction imaging.We theoretically investigate the band structures,equi-frequency surfaces,electromagnetic wave propagation,and the image intensity distributions in a two-dimensional hexagonal photonic crystal consisting of hollow components.It is found that,in contrast to a hexagonal photonic crystal consisting of solid dielectric cylinders of the same radius,photonic crystals with hollow components can be used to optimize the all-angle negative refraction.Numerical simulations show that the transmission efficiency and resolution of image can be enhanced by changing the radii of the hollow air rods.
基金Supported by the National Natural Science Foundation of China under Grant No 61275014the Science and Technology Program of Shandong Province under Grant No 2011GGH20119the Natural Science Foundation of Shandong Province under Grant No ZR2011FQ011.
文摘A method to extract phase shifts and reconstruct the object wave in generalized phase-shifting interferometry(GPSI)is proposed.The phase distribution of a standard phase object and the least-square method are used to extract phase shifts over a wide range from 0 to𝜌π.Consequently,the tested object wave can be further reconstructed with the extracted phase shifts.It is accurate and applicable for GPSI of any frame number𝑂(N𝑂≥2).Computer simulation has verified its feasibility and validity.
