2009, 7(8) Column
Chinese Optics Letters 第7卷 第8期
We investigate the optical bistability and multistability behaviors in a closed three-level \Lambda-type atomic system. By adding a sideband on either hand of the transitions which are originally coupled by a coherent control field and a coherent probe field to disturb the two-photon resonance, bistability occurs due to two-channel interference. Increasing the sideband Rabi frequency leads to the switching from bistability to tristability. When the sideband simultaneously couples with both hands, we can easily obtain quadrastability.
双稳 多稳 多通道 020.1670 Coherent optical effects 190.1450 Bistability The potential energy curves (PECs) of BO molecule, including \sum+ and \prod symmetries with doublet spin multiplicities, are obtained employing multi-reference configuration interaction (MRCI) method and Dunning’s correlation consistent basis sets. The analytical potential energy functions (APEFs) are fitted using the Murrell-Sorbie (MS) function and the least square method. Based on the PECs, the spectroscopic constants of the states have been determined and compared with the theoretical and experimental results available to affirm the accuracy and liability of the calculations. The root-mean-square (RMS) errors between the fitted results and the ab initio values are too little in comparison with the chemical accuracy (349.755 cm-1. It is shown that the present APEFs are accurate and can display the interaction between the atoms well. The present APEFs can be used to construct more complicated APEF or do some dynamic investigations.
势能曲线 解析势能函数 多参考组态相互作用 光谱常数 020.0020 Atomic and molecular physics 300.6390 Spectroscopy, molecular Optimized guided mode resonant structure as thermooptic sensor and liquid crystal tunable filterDownload:691次
Applicability of guided mode resonant structures to tunable optical filtering and sensing is demonstrated using nematic liquid crystals. As a sensor, a minimum refractive index detectivity of 10^{-5} is demonstrated while as a tunable filter, tunability range of few tens of nanometers with 2-nm bandwidth is presented. The optimum design is achieved by maximizing the evanescent field region in the analyte which maximizes the overlap integral. The device can be operated in reflection or transmission modes at normal incidence. It can also be operated at a single wavelength by measuring the angular profile of the light beam.
波导管共振 光学传感器 可调滤光片 液晶 050.5745 Resonance domain 050.6624 Subwavelength structures 130.2790 Guided waves 230.3720 Liquid-crystal devices The numerical study on the performance of large-mode-area (LMA) fibers coiled onto a spool in high power amplifier is carried out as the bend-induced distortion of fiber modes severely affects the output characteristics of amplifier systems. The variations for high-order mode bend distortion with different orientations relative to the plane of the fiber bend are observed and shown. Concerning the practical applications, a bend-resistant LMA fiber with the mode area larger than 1000 \mum2 and excellent high-order mode suppression is designed completely by optimizing the refractive index (RI) and dopant profile. The results indicate that a hybrid profile of RI and dopant is the best choice for LMA fiber with coiling.
大模面积光纤 高功率光纤放大器 弯曲畸变 有效模场面积 高阶模抑制 060.2280 Fiber design and fabrication 140.3510 Lasers, fiber 060.2320 Fiber optics amplifiers and oscillators Dual-wavelength FBG inscribed by femtosecond laser for simultaneous measurement of high temperature and strainDownload:845次
A novel fiber Bragg grating (FBG) with two transmission dips in 1310- and 1550-nm regions is proposed and inscribed by an infrared femtosecond laser. Formed by multi-photon ionization, this type of grating can withstand temperature as high as 800 degrees which makes it suitable for harsh environment sensing. In addition, the temperature and strain affect these two dips in different ways, which enables simultaneous strain and temperature sensing. The fabrication, spectrum characterization, and temperature performance of this grating are introduced.
布拉格光栅 飞秒激光 光纤传感器 060.2370 Fiber optics sensors 140.7090 Ultrafast lasers 050.2770 Gratings A novel method for distortion-free optical pulse transmission is theoretically proposed and simulated, in which two time lenses formed by dispersion fibers and quadratic phase modulations are utilized. One is used as an optical inverse Fourier transformation (OIFT) device to transform the initial time-domain data to frequency-domain one at the transmitter and the other as an optical Fourier transformation (OFT) device to recover the data at the receiver. By using the unchanged spectral envelope in linear optical fiber communication, the initial data can be recovered. Through simulations, a 10\times100 Gb/s intensity-modulated direct-detection (IM-DD) dense wavelength division multiplexing (DWDM) system over 2000-km transmission without the compensation for polarization mode dispersion (PMD) and dispersion slope is achieved, which can be used to upgrade the current 10-Gb/s IM-DD system to a 100-Gb/s one directly.
光频域强度调制-直接检测通信系统 光傅里叶变换和反变换器件 时间透镜 平方相位调制器 PMD补偿 060.0060 Fiber optics and optical communications 070.0070 Fourier optics and signal processing A new but simply implemented optical clock recovery scheme for optical time-division multiplexing (OTDM) systems based on stimulated Brillouin scattering (SBS) effect is presented and demonstrated experimentally. According to the unequal-amplitude even-multiplexed OTDM signals, the frame clock is extracted. In addition, the clock with multiple tributary rates is recovered from 160-Gb/s OTDM signal in simulation by utilizing the clock recovery module.
受激布里渊 时钟恢复 光时分复用 060.0060 Fiber optics and optical communications 060.2330 Fiber optics communications 290.0290 Scattering 290.5830 Scattering, Brillouin Hopfield neural network-based image restoration with adaptive mixed-norm regularizationDownload:590次
To overcome the shortcomings of traditional image restoration model and total variation image restoration model, we propose a novel Hopfield neural network-based image restoration algorithm with adaptive mixed-norm regularization. The new error function of image restoration combines the L2-norm and L1-norm regularization types. A method of calculating the adaptive scale control parameter is introduced. Experimental results demonstrate that the proposed algorithm is better than other algorithms with single norm regularization in the improvement of signal-to-noise ratio (ISNR) and vision effect.
图像复原 神经网络 混合范数 规整化 100.3020 Image reconstruction-restoration 100.3190 Inverse problems 200.4260 Neural networks Contrast enhancement is particularly important for imaging of weakly absorbing materials. We demonstrate the inherent contrast-enhancement effect at the edges of a transparent object by using a conventional pulsed terahertz imaging setup without additional modification of the system design. We provide both experimental and theoretical evidence suggesting that this effect is a consequence of the frequency-dependent energy loss of the terahertz radiation induced by edge diffraction. The influence of the phase step of the broadband terahertz pulses on the edge contrast is discussed.
边缘衍射 太赫兹成像 相位阶跃 110.6795 Terahertz imaging 050.1940 Diffraction 120.4290 Nondestructive testing We present a category of novel photothermal (PT) microactuators. Each microactuator consists of two PT arms that are jointed at the free end and connected to an anchor at the fixed end. When a laser beam irradiates one of the arms (called hot arm, and the other is cold arm), light energy is absorbed and converted into heat. The asymmetric thermal expansion of the hot and cold arms results in lateral deflection. Based on conduction heat transfer theory and heat dissipation mechanism, we study the PT effects and establish the theoretical model of PT expansion for the microactuators. The temperature distribution and the linear thermal expansion can be numerically calculated. The analytical solution provides an insight into the operation of the actuators and predicts the performance of the actuators with new designs. A symmetry microactuator and a microswitch as the prototypes have been fabricated and tested. The experimental results are in good agreement with the theoretical predictions and prove the feasibility of the novel PT microactuators.
光热效应 温度 微加工 微结构 激光 120.6780 Temperature 350.5340 Photothermal effects 220.4000 Microstructure fabrication 230.3990 Micro-optical devices 140.3460 Lasers Dynamic behaviors of the erbium-doped fiber laser (EDFL) with dual-frequency loss modulation are experimentally investigated. Frequency-locked states with their winding numbers which form the devil's staircase are observed in this kind of lasers. In the unlocked regions, the output state changes from quasiperiodicity to chaos under increasing modulation index, which demonstrates a different route to chaos from the conventional loss-modulated EDFLs with a single modulation frequency. The chaos output in the dual-frequency loss-modulated EDFLs shows less harmonic components of the modulation frequency in the corresponding power spectrum, indicating the improvement of the randomness of the chaotic signals.
掺铒光纤激光器 损耗调制 混沌 锁频 准周期 140.1540 Chaos 140.3500 Lasers, erbium Thermally stable region of a seven-rod resonator is theoretically investigated. A plane-plane symmetric resonator, where the distance between two neighbor rods is two times of that between the rods and the mirrors, is adopted because of its large stable range. Based on the investigation, a seven-rod resonator with an average output power of 3.79 kW and an optical-to-optical efficiency of 53% is developed.
多棒谐振腔 热稳区 LD侧泵 140.3480 Lasers, diode-pumped 140.4780 Optical resonators 140.3530 Lasers, neodymium A diode-pumped continuous-wave (CW) mode-locked Nd:YVO4/KTP green laser with semiconductor saturable absorber mirror (SESAM) is demonstrated. The maximum output power of CW mode-locked green laser is obtained to be 552 mW at the incident pump power of 7.25 W, corresponding to an optical-optical conversion efficiency of about 7.6%. The 532-nm CW mode-locked pulse duration is estimated to be about 8.4 ps with the repetition rate of 87 MHz.
Nd:YVO4激光器 被动锁模 腔内倍频 140.3530 Lasers, neodymium 140.4050 Mode-locked lasers 140.3515 Lasers, frequency doubled We report the fabrication of a novel high-power vertical-cavity surface-emitting laser (VCSEL) with radial bridge electrodes in this letter. The analysis shows that the radial bridge electrodes can reduce the p-type distributed Bragg reflector (p-DBR) electric and thermal resistance, and improve the device beam quality. The high-power radial brigde electrode VCSELs with 200-\mum aperture have been made and tested. The testing results show that the differential resistance of the VCSEL is 0.43 \Omega and the maximal continuous-wave (CW) output power is 340 mW, 1.7 times higher than the conventional electrode device. Its thermal resistance is 0.095 \Degress/mW, and its near-field pattern exhibits a homogeneous distribution. The high-power radial bridge electrode VCSEL has better temperature and opto-electric characteristics.
高功率半导体激光 垂直腔面发射激光器 径向桥电极 热阻 140.0140 Lasers and laser optics 140.7260 Vertical cavity surface emitting lasers 250.7260 Vertical cavity surface emitting lasers 140.6810 Thermal effects Pulsed-pumped optical fiber amplifierDownload:667次
With the use of pulsed pumping, an optical fiber amplifier with all-fiber structure is developed based on the fused tapered fiber combiner and Yb+{3+}-doped double cladding fiber (YDCF). From the experimental results, 47-dBm peak power and 100-ns pulse duration are obtained when the repetition rate of pumping pulses is 100 Hz. The gain of the amplifier is up to 30 dB. It is shown that due to the use of pulsed pumping, pump light emits only when the signal light reaches the amplifier and thus the amplified spontaneous emission (ASE) is significantly suppressed.
脉冲泵浦 双包层掺镱光纤放大器 全光纤结构 140.4480 Optical amplifiers 230.4480 Optical amplifiers 060.2320 Fiber optics amplifiers and oscillators We find the femtosecond laser induced microripple beside the focused femtosecond laser spot and along the movement direction of the laser spot on polydimethylsiloxane (PDMS) surface. The microripple may be due to the melting of PDMS induced by femtosecond laser pulses and the subsequent cool-down solidification of the melting PDMS along with the movement of the femtosecond laser spot. This result will be helpful to understand the interaction between the femtosecond laser and the polymer.
飞秒激光 PDMS 微波纹 140.3390 Laser materials processing 140.3440 Laser-induced breakdown 140.6810 Thermal effects We report the fast lateral photovoltaic effect in pure congruent LiNbO3 crystal induced by pulsed laser and continuous wave laser with wavelengths of 355, 532, and 1064 nm. A typical ultrafast photovoltage can be observed on the surface perpendicular to the c axis, with the rise time of 1.5 ns and the full-width at half-maximum of 1–2 ns, when the laser pulse inhomogeneously irradiates on the crystal. The peak open-circuit photovoltages show a linear dependence on the incident laser intensities. The mechanism of the photovoltaic characteristics is proposed.
超快光生伏特 横向光生伏特效应 铌酸锂 160.3730 Lithium niobate 160.2260 Ferroelectrics 320.7120 Ultrafast phenomena Micro stereo lithography is a kind of technology utilizing the solidified effect that photo curable polymer will appear under ultraviolet (UV) laser exposure. It is widely used in three-dimensional (3D) micro fabrication. We get the experimental values of a pair of UV laser curing coefficients, absorption coefficient and critical curing energy, of curable resin by fitting the calculation results of the Gaussian beam theory and experimental curing results. The theoretical relation between the curing unit’s shape and the exposure features of time and intensity of convergent Gaussian beam is presented. The calculation and experimental results of curing unit under different conditions agree well with each other. This research offers a steady base for further research about the improvement of resolution.
微细光成型模拟固化单元 220.3740 Lithography 220.4000 Microstructure fabrication 220.4610 Optical fabrication The tracking precision of laser tracking system is affected by the angular resolution of quadrant avalanche photodiode. According to the detecting principle of quadrant avalanche photodiode, the light spot area, the optical intensity distribution, the non-uniformity of response, and the signal-to-noise ratio (SNR) that affect the linearity of the detector are studied. The light optical spot area and the optical intensity distribution can be adjusted through software. The non-uniformity of response and the SNR are influenced by the noise of the detector. Because the noise is affected by the optical intensity of the incident laser, it is difficult to obtain the law of the linearity caused by noise. When the light spot area and the optical intensity distribution are fixed, the other factors can be measured. With the detector scanned in raster scanning mode, the non-uniformity of response is measured at different SNRs. The linearity of detector is measured by a moving target that can reflect the illuminating laser to the detector in diffuse reflection mode. The nonlinear error of the linearity of detector can be minimized by increasing the SNR.
四象限雪崩探测器 线性度 非线性误差 响应率 信噪比 280.3640 Lidar 140.3300 Laser beam shaping 140.3290 Laser arrays Laser Doppler vibrometer (LDV) has a potential application prospect in remote sensing. Based on the correlation theories of heterodyne detection, a LDV system with a configuration of all fiber and heterodyne techniques is developed to detect the sound signal through the vibration of glass. Experimental results show that the LDV system has an ability to acquire the real-time speech signal 25 m away through glass. While, the system signal-to-noise ratio (SNR) value decreases with the increase of the glass thickness and the detection distance.
激光多普勒振动计 外差探测 正交解调 280.3340 Laser Doppler velocimetry 060.2840 Heterodyne 070.1170 Analog optical signal processing Raman spectra are used for studying the structure and protein, nucleic acid, lipid, and carbohydrate contents, while cervical cancer cells irradiated by X rays of different doses are cultivated for 24 h. After irradiation by X rays, the following results are obtained. (1) Some 12-Gy groups move to the 1237-cm-1 band in compared with the control group’s 1240-cm-1 band; after irradiation by 6-Gy X ray, the 1662-cm-1 band of amide I has a blue shift of 10 cm-1 The above two parts show that because of X ray irradiation, some proteins’ random coil structures have transformed into \beta folding. (2) The 759-cm-1 band disappear in the 6-Gy group; the 570-cm-1 band of every group has a red shift, but the changes in intensity are different; the 1335-cm-1 band in every group has a blue shift, and all their intensities increase. These show that although the 570-, 759-, and 1335-cm-1 bands all belong to the tryptophan residue indole ring vibration, the molecular vibration energy structures which produce scattering lights are different. (3) The 786-cm-1 band only has a blue shift of 3 cm-1 in the 6-Gy group, and the non-hydrogen band of the phosphoric acid diester (O=P=O) increases. The frequency deviation of the 1089-cm-1 band is erratic, and the bent symmetry stretch vibration conformation of phosphoric acid diester key (O=P=O) in the nucleic acid is complex. (4) The 1570-cm-1 band has a blue shift, and its intensities all decrease, while the C=C conjugated duplet bond oxidizes, and the content of C=C decreases.
拉曼光谱 宫颈癌细胞 X射线 300.6450 Spectroscopy, Raman 300.6560 Spectroscopy, x-ray 170.1530 Cell analysis 340.6720 Synchrotron radiation Influence of interface roughness on the reflectivity of Tungsten/boron-carbide (W/B4C) multilayers varying with bi-layer number, N, is investigated. For W/B4C multilayers with the same design period thickness of 2.5 nm, a real-structure model is used to calculate the variation of reflectivities with N=50, 100, 150, and 200, respectively. Then, these multilayers are fabricated by a direct current (DC) magnetron sputtering system. Their reflectivity and scattering intensity are measured by an X-ray diffractometer (XRD) working at Cu K\alpha line. The X-ray reflectivity measurement indicates that the reflectivity is a function of its bi-layer number. The X-ray scattering measured results show that the interface roughness of W/B4C multilayers increases slightly from layer to layer during multilayer growing. The variation of the reflectivity and interface roughness with bi-layer number is accurately explained by the presented real-structure model.
多层膜 粗糙度 反射率 散射 310.0310 Thin films 220.0220 Optical design and fabrication 230.0230 Optical devices 340.0340 X-ray optics The optical properties of self-assembled InAs quantum dots (QDs) on GaAs substrate grown by metal-organic chemical vapor deposition (MOCVD) are reported. Photoluminescence (PL) measurements prove the good optical quality of InAs QDs, which are achieved using lower growth temperature and higher InAs coverage. At room temperature, the ground state peak wavelength of PL spectrum and full-width at half-maximum (FWHM) are 1305 nm and 30 meV, respectively, which are obtained as the QDs are finally capped with 5-nm In0.06Ga0.94As strain-reducing layer (SRL). The PL spectra exhibit two emission peaks at 1305 and 1198 nm, which correspond to the ground state (GS) and the excited state (ES) of the QDs, respectively.
InAs量子点 光学特性 金属有机化学汽相沉积 310.1860 Deposition and fabrication 250.5230 Photoluminescence 310.3840 Materials and process characterization Pearlescent coatings become highly popular to the modern generation of color rendering materials due to their unique color effect. However, it is quite challenging to evaluate its color appearance by traditional color measurement. A low-cost camera is a highly efficient device for multi-geometry color appearance estimation for pearlescent bottles, which has been achieved through the camera characterization, sample image capturing, and then mathematical transforming from RGB (red, green, and blue) values to color appearance attributes based on the color appearance model of CIECAM02. A tele-spectroradiometer for physical measurement together with visual assessment is applied for comparison with the camera method to evaluate the accuracy of camera predictions and discuss the applicability of CIECAM02. The experimental results indicate that the camera data have strong correlation with the physical measurement and also fit well with visual data except for a slight slope shift existing in lightness due to a divinable psychophysical magnitude variation for spatial-dependent color samples. Hence it is feasible to estimate the color appearance of pearlescent bottles using a digital camera.
珠光特性 多角度 相机特征化 色貌模型 幅度估计 330.1710 Color, measurement 330.4595 Optical effects on vision 110.2970 Image detection systems We present a novel method of color reproduction from desktop displays to projectors via visual assessment. The model is based on visual matching nine color patches between a display and a projector. The effects of the method to improve color reproduction are tested for 30 samples by visual and color difference evaluations. The expeirmental results of visual evaluation show that the color reproduction is improved by 87.5%. The maximum, minimum, and average color differences between the displayed colors and the projected ones before and after correction are 28.94, 4.35, 16.78, 16.51, 0.64, and 3.51 \DeltaE^{*}_{ab} units respectively, which are consistent with the results of visual evaluation.
显示器 投影仪 颜色再现 视觉匹配 330.1720 Color vision 330.1730 Colorimetry 动态信息
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