Journals >Chinese Optics Letters
Contents
2007
Volume: 5 Issue 12
15 Article(s)
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Research Article
A polynomial hybrid reflection model and measurement of its parameters based on images of sample
Lei Yang, and Jiuqiang Han
Reflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance. But the ratio of diffuse and specular reflection decided manually has no clear meaning. We prReflectance model is a basic concept in computer vision. Some existing models combining the classical diffuse reflectance model and those for surfaces containing specular components can approximately describe real reflectance. But the ratio of diffuse and specular reflection decided manually has no clear meaning. We propose a new polynomial hybrid reflectance model. The reflectance map equation with a known shape (for example cylinder) as a sample is used to estimate parameters of the proposed reflectance model by least square regression algorithm. Then the reflectance parameters for surfaces of the same class of materials can be determined. Experiments are performed for a metal surface. The synthesis images produced by the proposed method and existing ones are compared with the real acquired image, and the results show that the proposed reflectance model is suitable for describing real reflectance..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 683 (2007)
Double-image encryption based on joint transform correlation and phase-shifting interferometry
Lina Shen, Jun Li, and Hongsen Chang
An image encryption method combining the joint transform correlator (JTC) architecture with phase-shifting interferometry to realize double random-phase encoding is proposed. The encrypted field and the decrypting key are registered as holograms by phase-shifting interferometry. This method can encrypt two images simulAn image encryption method combining the joint transform correlator (JTC) architecture with phase-shifting interferometry to realize double random-phase encoding is proposed. The encrypted field and the decrypting key are registered as holograms by phase-shifting interferometry. This method can encrypt two images simultaneously to improve the encryption efficiency of the methods based on JTC architecture, and eliminate the system alignment constraint of the methods based on Mach-Zehnder interferometer (MZI) architecture. Its feasibility and validity are verified by computer simulations. Moreover, image encryption and decryption can be achieved at high speed optically or digitally. The encrypted data are suitable for Internet transmission..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 687 (2007)
Self-imaging effect in photonic crystal multimode waveguides exhibiting no band gaps
Tianbao Yu, Xiaoqing Jiang, Qinghua Liao, Wei Qi, Jianyi Yang, and Minghua Wang
The properties of the propagating field in multimode photonic crystal waveguides (PCWs) exhibiting no photonic band gaps (PBGs) are investigated. The transmission spectrum shows that the input field can be guided with high efficiency, and resemble index-guided modes owing to the combination of total internal reflectionThe properties of the propagating field in multimode photonic crystal waveguides (PCWs) exhibiting no photonic band gaps (PBGs) are investigated. The transmission spectrum shows that the input field can be guided with high efficiency, and resemble index-guided modes owing to the combination of total internal reflection (TIR) and distributed Bragg reflection (DBR). Self-imaging effect happens and the filling fraction determines the beating lengths. The rows of air holes decide DBR coming from the mirrors on both sides of the guiding region, which governs the transmission spectrum. It provides a new way to realize the components for both polarizations by combining PBG and TIR effects in PCWs..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 690 (2007)
Tunable photonic crystals based on ferroelectric and ferromagnetic materials by focused ion beam
Ziyou Zhou, Xiaoyue Huang, Raghav Vanga, and Rong Li
By making photonic crystals in ferroelectric and ferromagnetic materials, field-provoked tunability of photonic crystals is broadening the interest in new applications of on-chip photonic devices. We report a nano-precise fabrication of various designs of photonic crystals in these non-conventional materials using the By making photonic crystals in ferroelectric and ferromagnetic materials, field-provoked tunability of photonic crystals is broadening the interest in new applications of on-chip photonic devices. We report a nano-precise fabrication of various designs of photonic crystals in these non-conventional materials using the focused ion beam milling technique. Standard methods are developed and parameters for different materials are calibrated. Optical responses such as bandgaps and polarization status changing from planar film waveguide system with these patterns have been examined on ferromagnetic materials..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 693 (2007)
Study on optical gain of one-dimensional photonic crystals with active impurity
Zhenghua Li, Tinggen Shen, Xuehua Song, Junfeng Ma, Yong Sheng, and Gang Wang
Localized fields in the defect mode of one-dimensional photonic crystals with active impurity are studied with the help of the theory of spontaneous emission from two-level atoms embedded in photonic crystals. Numerical simulations demonstrate that the enhancement of stimulated radiation, as well as the phenomena of trLocalized fields in the defect mode of one-dimensional photonic crystals with active impurity are studied with the help of the theory of spontaneous emission from two-level atoms embedded in photonic crystals. Numerical simulations demonstrate that the enhancement of stimulated radiation, as well as the phenomena of transmissivity larger than unity and the abnormality of group velocity close to the edges of photonic band gap, are related to the negative imaginary part of the complex effective refractive index of doped layers. This means that the complex effective refractive index has a negative imaginary part, and that the impurity state with very high quality factor and great state density will occur in the photonic forbidden band if active impurity is introduced into the defect layer properly. Therefore, the spontaneous emission can be enhanced, the amplitude of stimulated emission will be very large and it occurs most probably close to the edges of photonic band gap with the fundamental reason, the group velocity close to the edges of band gap is very small or abnormal..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 696 (2007)
20-GHz optical pulse source based on cascaded electroabsorption modulators
Yuanshan Liu, Jianguo Zhang, and Wei Zhao
A high-quality low-timing-jitter 20-GHz optical pulse train is generated by using two cascaded sinusoidally driven electroabsorption modulators (EAMs) at very low bias voltage of -0.8 V in conjunction with a tunable distributed feedback (DFB) semiconductor laser. An approximate transform-limited optical pulse, with theA high-quality low-timing-jitter 20-GHz optical pulse train is generated by using two cascaded sinusoidally driven electroabsorption modulators (EAMs) at very low bias voltage of -0.8 V in conjunction with a tunable distributed feedback (DFB) semiconductor laser. An approximate transform-limited optical pulse, with the pulse width less than 7 ps, the spectral width of 0.3 nm, and the side-mode suppression ratio (SMSR) above 20 dB, is obtained by tuning the optical delay line..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 700 (2007)
Fabrication of SiO2 microdisk optical resonator
Wei Wei, Xiaowei Wu, Shaojun Fu, Yong Wang, Yuanji Pei, Yunfeng Xiao, and Zhengfu Han
The silica microdisk optical resonator which exhibits whispering-gallery-type modes with quality factors of 9.67*10^(4) is fabricated with photolithographic techniques. Reactive ion beam etching (RIBE) is used to get the silica disks with photoresist masks on SiO2/Si made by standard ultraviolet (UV) photolithography, The silica microdisk optical resonator which exhibits whispering-gallery-type modes with quality factors of 9.67*10^(4) is fabricated with photolithographic techniques. Reactive ion beam etching (RIBE) is used to get the silica disks with photoresist masks on SiO2/Si made by standard ultraviolet (UV) photolithography, and spontaneous silicon etching by XeF2 is used to fabricate the silicon micropillars. This fabrication process can control the microcavity geometry, leading to high experiment repeatability and controllable cavity modes. These characteristics are important for many applications in which the microcavity is necessary, such as the quantum gate..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 703 (2007)
Applying the reference-wavelength method to improve the precision of glucose measurement by near infrared spectroscopy
Wenliang Chen, Kexin Xu, Yu Li, and Yun Chen
The reference-wavelength method is proposed to diminish the influence of noises on glucose measurement by differentially processing two signals at the reference and measuring wavelengths. At the reference wavelength, the radiation intensity is insensitive to the changes of glucose concentration. Therefore, it can be usThe reference-wavelength method is proposed to diminish the influence of noises on glucose measurement by differentially processing two signals at the reference and measuring wavelengths. At the reference wavelength, the radiation intensity is insensitive to the changes of glucose concentration. Therefore, it can be used as the internal reference to estimate the noise and then to extract the effective glucose signal at the other wavelengths. The validation experiments are constructed in the non-scattering samples with the reference wavelength of glucose at 1525 nm. The results show that the reference-wavelength-based glucose-specific signal extracting method can largely improve the glucose prediction precision from 17.56 to 8.87 mg/dL in the two-component experiment and from 26.82 to 9.94 mg/dL in the three-component experiment..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 706 (2007)
Field enhancement analysis of an apertureless near field scanning optical microscope probe with finite element method
Weibin Chen, and Qiwen Zhan
Plasmonic field enhancement in a fully coated dielectric near field scanning optical microscope (NSOM) probe under radial polarization illumination is analyzed using an axially symmetric three-dimensional (3D) finite element method (FEM) model. The enhancement factor strongly depends on the illumination spot size, tapePlasmonic field enhancement in a fully coated dielectric near field scanning optical microscope (NSOM) probe under radial polarization illumination is analyzed using an axially symmetric three-dimensional (3D) finite element method (FEM) model. The enhancement factor strongly depends on the illumination spot size, taper angle of the probe, and the metal film thickness. The tolerance of the alignment angle is investigated. Probe designs with different metal coatings and their enhancement performance are studied as well. The nanometric spot size at the tip apex and high field enhancement of the apertureless NSOM probe have important potential application in semiconductor metrology..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 709 (2007)
Effects of chromophore concentration and film thickness on thermo-optic properties of electro-optic fluorinated polyimide films
Hongxiang Song, and Chengxun Wu
Electro-optic (EO) effect and thermo-optic (TO) effect are jointly considered on the basis of field-induced and temperature-affected perturbations of the operating point in waveguide components. TO coefficients of EO fluorinated polyimide films with side-chain azobenzene chromophore were measured by attenuated-total-reElectro-optic (EO) effect and thermo-optic (TO) effect are jointly considered on the basis of field-induced and temperature-affected perturbations of the operating point in waveguide components. TO coefficients of EO fluorinated polyimide films with side-chain azobenzene chromophore were measured by attenuated-total-reflection (ATR) technique at different temperatures with TE- and TM-polarized lights, respectively. It is found that the absolute values of TO coefficients increase with the increments of both chromophore concentration and film thickness, but the polarization dependence of TO coefficients increases with the increment of chromophore concentration and decreases with the increment of film thickness..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 712 (2007)
Frequency selective surface with a flat topped passband
Hongyan Jia, Jinsong Gao, Xiaoguo Feng, and Qingwen Meng
Two frequency selective surface (FSS) configurations with flat topped passband are presented in this paper. One configuration is single layer FSS with lambda/4 thickness dielectric loaded on both sides, and the other is double layers FSS. Based on the modal matching method, the frequency response properties including aTwo frequency selective surface (FSS) configurations with flat topped passband are presented in this paper. One configuration is single layer FSS with lambda/4 thickness dielectric loaded on both sides, and the other is double layers FSS. Based on the modal matching method, the frequency response properties including angle effect and polarization effect of both FSS configurations are analyzed, and the plots of the frequency versus transmission coefficient are obtained for different incident angles and polarizations. It is shown that the structure with the single layer FSS embedded centrally in the lambda/2 thickness dielectric has a wider flat top bandwidth of 6.8 GHz than that of the double layers FSS of 3 GHz. In addition, the fabrication of single layer is relatively easier than the double layers FSS..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 715 (2007)
Quartz optical filter for wavelength selection of frequency-doubled laser based on optical rotatory dispersion effect
Shan Zhang, Fuquan Wu, Wendi Wu, and Haifeng Wang
Based on the optical rotatory dispersion effect, an optical filter for selecting the second harmonic of a frequency-doubled laser is constructed from quartz in combination with polarizers. The operating principle is analyzed by matrix formulation, and the result indicates that the second harmonic of a frequency-doubledBased on the optical rotatory dispersion effect, an optical filter for selecting the second harmonic of a frequency-doubled laser is constructed from quartz in combination with polarizers. The operating principle is analyzed by matrix formulation, and the result indicates that the second harmonic of a frequency-doubled laser will be obtained when the rotation angle has a difference of (2n+1)'pi'/2 (n=0, 1, 2, 3, ...) between the two polarizations of the second-harmonic laser and the fundamental laser. The spectrum of the output laser is taken by the AQ-6315A spectrometer, and the experimental results are in good agreement with the theoretical results..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 717 (2007)
Depolarization of backscattered linearly polarized light from ZnO thin film
Linxing Shi, Liyong Jiang, Hailin Wang, and Xiangyin Li
The depolarization behavior of backscattered linearly polarized light from ZnO thin film was investigated experimentally. The results show that the characteristics are related to both the polarization orientation and wavelength of linearly polarized incident light. When the incident light is s-polarized, the depolarizaThe depolarization behavior of backscattered linearly polarized light from ZnO thin film was investigated experimentally. The results show that the characteristics are related to both the polarization orientation and wavelength of linearly polarized incident light. When the incident light is s-polarized, the depolarization behaviors are different for different wavelengths. When the incident light is p-polarized, the depolarization behaviors, on the contrary, are similar for different wavelengths. In addition, there is an optimal incident angle for depolarization of linearly polarized light with different wavelengths, which is equal to their effective Brewster angles, respectively..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 720 (2007)
Laser-induced damage of high reflectors for Ti:sapphire laser system
Jianke Yao, Weiqiang Zeng, Zhengxiu Fan, Hongbo He, and Jianda Shao
A broadband (~176 nm, R>98%, 'lambda'0=800 nm) and high laser-induced damage threshold (LIDT=2.4J/cm2) TiO2/HfO2/SiO2 high reflector (HR) for Ti:sapphire chirped-pulse amplification (CPA) laser system is fabricated by the electron beam evaporation. The refractive index and extinction coefficient of TiO2 A broadband (~176 nm, R>98%, 'lambda'0=800 nm) and high laser-induced damage threshold (LIDT=2.4J/cm2) TiO2/HfO2/SiO2 high reflector (HR) for Ti:sapphire chirped-pulse amplification (CPA) laser system is fabricated by the electron beam evaporation. The refractive index and extinction coefficient of TiO2 and HfO2 films are calculated from single-layer films' transmittance spectra. The properties of HR are mainly determined by the high refractive index material. The high refractive index leads to wide bandwidth. A low extinction coefficient indicates low absorption and high LIDT. The possible damage mechanism of HR is discussed..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 724 (2007)
Laser-induced damage threshold in n-on-1 regime of Ta2O5 films at 532, 800, and 1064 nm
Cheng Xu, Jianke Yao, Jianyong Ma, Yunxia Jin, and Jianda Shao
Ta2O5 films were prepared with conventional electron beam evaporation and annealed in O2 at 673 K for 12 h. Laser-induced damage thresholds (LIDTs) of the films were performed at 532 and 1064 nm in 1-on-1 regime firstly, and then were performed at 532, 800, and 1064 nm in n-on-1 regime, respectively. The results showedTa2O5 films were prepared with conventional electron beam evaporation and annealed in O2 at 673 K for 12 h. Laser-induced damage thresholds (LIDTs) of the films were performed at 532 and 1064 nm in 1-on-1 regime firstly, and then were performed at 532, 800, and 1064 nm in n-on-1 regime, respectively. The results showed that the LIDTs in n-on-1 regime were higher than that in 1-on-1 regime at 532 and 1064 nm. In addition, in n-on-1 regime, the LIDT increased with the increase of wavelength. Furthermore, both the optical property and LIDT of Ta2O5 films were influenced by annealing in O2..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 12, 727 (2007)
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