Differential evolution algorithm is used to solve the inverse problem of strain distribution in fiber Bragg grating (FBG). Linear and nonlinear strain profiles are reconstructed based on the reflection spectra. An approximate solution could be obtained within only 50 rounds of evolutions. Numerical examples show good agreements between target strain profiles and reconstructed ones. Online performance analysis illuminates the efficiency and practicality of differential evolution algorithm in solving the inverse problem of FBG.
A YVO4 crystal Gland-Foucasult prism is manufactured. The relationships between prism structure angle and view field angle are studied with different wavelengths. The results show that the prism with the structure angle of 28.18° has a good extinction ratio and the transmission characteristic in both visible and near-infrared regions.
We propose a new integrated method which covers addition of any two signed digit numbers in all-optical domain. To implement this scheme we have exploited some photo-refractive characters of optical non-linear materials, which may experience 0.1–0.2 dB attenuation loss as silica is used as non-linear medium. Moreover, the attenuation loss may be reduced to 0.001 dB/m if we consider the use of slow light at 1.56 μm.
The memory devices in multi-valued logic are of most significance in modern research. This paper deals with the implementation of basic memory devices in multi-valued logic using Savart plate and spatial light modulator (SLM) based optoelectronic circuits. Photons are used here as the carrier to speed up the operations. Optical tree architecture (OTA) has been also utilized in the optical interconnection network. We have exploited the advantages of Savart plates, SLMs and OTA and proposed the SLM based high speed JK, D-type and T-type flip-flops in a trinary system.
A high-bandwidth, high-sensitivity fully differential optoelectronic integrated receiver is implemented in a chartered 3.3 V standard 0.35 μm analog CMOS process. To convert the incident light into a pair of fully differential photo-currents, a novel fully differential photodetector is proposed, which is composed of two completely identical photodiodes. The measurement results show that the receiver achieves a 1.11 GHz 3 dB bandwidth and a −13 dBm sensitivity for a 10−12 bit error at 1.5 Gb/s data rate under illumination by 850 nm incident lights.
The staggered InGaN quantum well (QW) structure and the conventional InGaN QW structure for the emission at a particular wavelength of 400 nm are designed and theoretically investigated, including the distribution of the carriers’ concentration, the radiative recombination rate, the Shockley-Read-Hall (SRH) recombination rate as well as the output performance and the internal quantum efficiency. The theoretical result indicates that the staggered QW structure offers significant improvement of carriers’ concentration in the QW, especially the hole concentration. The output power and the internal quantum efficiency also show 32.6 % and 32.5 % enhancement, respectively, in comparison with that of the conventional InGaN QW structure. The reduction of the electron overflow can be the main factor for the improvement of the optical performance for novel staggered InGaN QW structure.
A multi-channel free space optical interconnection component, fiber optic rotary joint, was designed using a Dove prism. When the Dove prism is rotated an angle of α around the longitudinal axis, the image rotates an angle of 2α. The optical interconnection component consists of the signal transmission system, Dove prim and driving mechanism. The planetary gears are used to achieve the speed ratio of 2:1 between the total optical interconnection component and the Dove prism. The C-lenses are employed to couple different optical signals in the signal transmission system. The coupling loss between the receiving fiber of stationary part and the transmitting fiber of rotary part is measured.
A model of universal single layer organic solar cells in metal-insulator-metal (MIM) representation involving field-dependent carrier mobility is set up. The current-voltage characteristics as well as the distribution of electron density, hole density and recombination rate on a set of parameters are simulated. Subsequently, the dependences of the short-circuit current density (Jsc) and open-circuit voltage (Voc) on the electron and hole zero-field mobility, excitation generation rate, energy gap, as well as electron-hole pair distance in an excitation are investigated. It is demonstrated that the enhancement of either the electron mobility or the hole mobility can contribute to the increase of Jsc in the devices. The increase of the hole mobility can lead to the improvement of both Jsc and Voc, and the simultaneous increase of the electron mobility and hole mobility will greatly elevate Jsc but maintain a steady Voc. Additionally, all the increases of the excitation generation rate, energy gap and electron-hole pair distance are beneficial to both the remarkable increases of Jsc and Voc of the devices.
Through analyzing theoretically the temperature effect of the optical-fiber Raman backscattering, a distributed temperature sensor is designed based on the single-mode fiber. Demodulation methods of temperature transduction are compared, and then the demodulation method using the ratio of the anti-Stokes and the Stokes Raman backscattering intensity is adopted. Both the hardware composition and the software realization of the system are introduced in detail. The experiment shows that the distinguishing ability of the temperature and that of the space are 1 °C and 2 m, respectively, and that the system response time is about 180 s with a sensing range of 5 km and with a temperature measurement range of 0–100 °C.
To obtain the coupling characteristics between slab wave-guides including left-handed material, we modify the coupled wave equations by using Maxwell’s equations. First, we obtain new-coupled wave equations and new-coupling coefficient. Second, the coupling between two identical five-layer slab wave-guides where their cores are left-handed material, but their claddings are right-handed materials is studied. The coupling coefficient for even TE mode which is more complex than that of the riglt-handed material slab wave guides, is obtained.
A passively Q-switched mode-locked Nd:GdYVO4 laser is successfully demonstrated by using a piece of GaAs crystal grown at low temperature as the passively saturated absorber and the output coupler. Fundamental properties of the Nd: GdYVO4 laser are investigated. The maximum average output power of 3.5 W is obtained by using plainsphere when the incident pumping power is 10 W, which corresponds to an optical-optical coversion efficiency of 35%. The threshold power for the Q-switching mode-locked is 1.2 W. The maximum average output power of 1.72 W is obtained by using GaAs when the incident pumping power is 10 W, mode-locked pulse train with a repetition rate of ∼113 MHz is achieved. At the incident laser pumping power of 7 W, the modulation depth is 100%.
SiC granule films were fabricated onto porous glass substrate by RF-magnetron sputtering. Photoluminescence (PL) measurements show that there are light emissions at three different wavelengths. Ultraviolet emission peaked at 360 nm originated from the band-band transmission of SiC nanoparticles with relatively small size. The 370 nm light emission was due to the luminescence of the nano-skeletons of porous glass that was formed during the etching of the glass substrate. The blue emission at about 460 nm was associated with the recombination of the excited electron and O-deficient defects appeared at the interface between SiC nanoparticles and the porous glass. Furthermore, the optimal PL performance was obtained when SiC deposited time was 1 h and the glass substrate was etched for 20 min in the annealing sample (450 °C).
Nitrogen-doped diamond films have been synthesized by EA-CVD (electron assisted chemical vapor deposition) technique. The quality and nitrogen impurity states of the diamond films are characterized by SEM, raman spectroscopy, XPS and EPR spectroscopy, respectively. The results show that the morphology changes from well-defined facets to cauliflower-like structures, the content of amorphous carbon increases and the quality drops with increasing the nitrogen flow rate. Furthermore, in the films, it can be observed that nitrogen impurity exists in the forms of Ns0, [N-V]0 and [N-V]−1. The contents of [N-V]0 and [N-V]−1 are lower when the nitrogen flow rate is relatively high, and the concentration of Ns0 varies from 15 ppm to 483 ppm.
The CIGS thin films are prepared by co-evaporation of elemental In, Ga and Se on the substrates of Mo-coated glasses at 400°C followed by co-evaporation of elemental Cu and Se at 550°C. We study the structural and electrical properties using XRD, XRF and Hall effect measurements. In general, Cu(In,Ga)5Se8 phase exists when Cu/(In+Ga) ratio is from 0.17 to 0.27, Cu(In,Ga)3Se5 phase exists for Cu/(In+Ga) ratio between 0.27 and 0.41, Cu2(In,Ga)4Se7 and Cu(In,Ga)2Se3.5 phases exist for Cu/(In+Ga) ratio between 0.41 and 0.61, and OVC(or ODC) and CuIn0.7Ga0.3Se2 phases exist when Cu/(In+Ga) ratio is from 0.61 to 0.88. With the increase of Cu/(In+Ga) ratio, the carrier concentrations of the films gradually increase, but the electrical resistivity gradually decreases.
Using transfer matrix method, the optical transmission properties of 1-D photonic crystals composed partially of negative refraction media are analyzed. The transmission spectra of periodic photonic crystal, chirped photonic crystal and apodized photonic crystal are numerically simulated respectively. By contrast with optical transmission properties of ordinary photonic crystals made of positive refraction media, the transmission spectra of apodized photonic crystal become unregular, the Bragg flat-headed area recurs but the peak of transmission does not change significantly. Futhermore, the band gap range of chirped photonic crystal diminishes gradually.
BP neural network is introduced to the fault location field of DWDM optical network in this paper. The alarm characteristics of the optical network equipments are discussed, and alarm vector and fault vector diagrams are generated by analyzing some typical instances. A 17 × 14 × 18 BP neural network structure is constructed and trained by using MATLAB. By comparing the training performances, the best training algorithm of fault location among the three training algorithms is chosen. Numerical simulation results indicate that the sum squared error (SSE) of fault location is less than 0.01, and the processing time is less than 100 ms. This method not only well deals with the missing alarms or false alarms, but also improves the fault location accuracy and real-time ability.
Mechanical vibration of target structures will modulate the phase function of radar backscattering, and will induce the frequency modulation of returned signals from the target. It generates a side bands of the target body Doppler frequency shift, which is helpful for target recognition. Based on this, a micro-Doppler atomic storehouse is built for the target recognition, and four kinds of common classifiers are used separately to perform the classified recognition. The simulation experimental results show that this method has high recognition rate above 90%.
The rapidness and stability of background extraction from image sequences are incompatible, that is, when a conventional Gaussian mixture models (GMM)is used to rebuild the background, if the background regions of the scene are changed, the extracted background becomes bad until the transition is over. A novel adaptive method is presented to adjust the learning rate of GMM in a Hilbert space. The background extraction is treated as a process of approaching to a certain point in the Hilbert space, so the real-time learning rate can be obtained by calculating the distance between the two adjacent extracted background images, and a judgment method of the stability of background is got too. Compared with conventional GMM, the method has both high rapidness and good stability at the same time, and it can adjust the learning rate online. The experiment shows that it is better than conventional GMM, especially in the transition process of background extraction.
Numerical simulation has been performed on the optical transmission enhancement properties of a one-dimensional Ag film single slit structure with grooves. The results show that the position, depth and number of the grooves have great influence on the optical transmission, and surface plasmon polariton and resonance mode are the primary factors. The maximal extinction ratio of 35.8 dB is achieved in the single slit structure by adjusting groove depth.
In the context of cavity quantum electrodynamics (QED), a potential scheme is proposed to generate entangled coherent states. The scheme includes twice interactions of two-level atoms with cavities. In the first interaction, two atoms are sent into a microwave cavity with the large detuning respectively. And then the second interaction is that the two atoms enter another microwave cavity and are driven by a resonant classical field meantime. When we choose the proper interaction time and make measurement on the two atoms, the two microwave cavity mode fields are determinatively entangled. In addition, it is easy to generalize the scheme to multi-cavity and multi-atom.