|
Review on photonic method for generating optical triangular pulses
Yiqun WANG, Li PEI, Song GAO, Jun HAO, Sijun WENG
Front Optoelec. 2013, 6 (2): 127-133.
https://doi.org/10.1007/s12200-013-0315-0
In this paper, several photonic generating methods for optical triangular pulses were reviewed. Four frontier research methods for generating optical triangular pulses were introduced, these four methods are respectively based on the frequency-to-time conversion, using normally dispersive fiber, by single-stage dual-drive Mach-Zehnder modulator (MZM), and using dual-parallel MZM. These four methods can be classified into two categories in terms of the optical source employed, such as mode-lock laser (MLL) and continuous-wave (CW) respectively. Compared with the methods based on MLL, those based on CW have many advantages, such as simpler structure, lower price, higher stability, more flexible and wider tunability. Besides, the method using single-stage drive MZM can generate versatile waveform optical pulses, which has better performance than the first two methods in tunable capability of both repetition rate and center wavelength. With the same driving signal applied, the optical source using the dual-parallel MZM can generate signal with higher frequency than that of using the single-stage MZM.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Optical devices based on multilayer optical waveguide
Sijun WENG, Li PEI, Ruifeng ZHAO, Junjie YANG, Yiqun WANG
Front Optoelec. 2013, 6 (2): 146-152.
https://doi.org/10.1007/s12200-013-0316-z
Optical waveguide is used to guide the transmission of light. This paper reviews multilayer optical waveguide and some devices based on it. The optical waveguide can be divided into single-layer and multilayer optical waveguides in general. Here, multilayer cylindrical waveguide and multilayer planar waveguides were mainly focused. The analyzing method and the structures of waveguides were also demonstrated in briefly. Both these multilayer optical waveguide used in different kinds of optical devices including optical modulator, laser, optical amplifier, optical switch and special fiber were further presented. At last, the principle and structure of these multilayer optical devices were compared.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Modelling overall transmitted efficiency at 1550 nm for polymer grating Silicon-on-insulator structure with defect
G. PALAI, T. K. DHIR, B. NATH, S. L. PATRA
Front Optoelec. 2013, 6 (2): 153-159.
https://doi.org/10.1007/s12200-013-0321-2
The overall transmitted efficiency at 1550 nm for Nylon-Teflon/Teflon-Nylon (N-T/T-N) grating Silicon-on-insulator (SOI) structure with defect in even and odd position was investigated in this paper. Different types of losses, such as absorption, reflection and diffraction, were considered to find out the overall transmitted efficiency. The absorption loss of both Nylon-Teflon (N-T) and Teflon-Nylon (T-N) structure is zero at the wavelength of 1550 nm. Reflectance of these structures was analyzed by using plane wave expansion (PWE) method. Simulation result showed that reflectance as well as transmittance was varied linearly with respect to defect at odd and even positions. Simulation is also done for the diffraction efficiency at 1550 nm with respect to detuning from Bragg’s angle, which was ranged from -0.4 rad to+0.4 rad. Finally, it was found that overall transmitted efficiency increased as even defect position varied from 2nd to 10th for both N-T/T-N grating SOI structure. Similarly, the overall transmitted efficiency decreased as odd defect position changed from 3rd to 11th for both N-T/T-N grating SOI structure.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
SAGCM avalanche photodiode with additional layer and nonuniform electric field
Abbas GHADIMI, Vahid AHMADI, Fatemeh SHAHSHAHANI
Front Optoelec. 2013, 6 (2): 199-209.
https://doi.org/10.1007/s12200-013-0317-y
This paper presents a new method to increase the speed of the separated absorption, grading, charge, and multiplication avalanche photodiode (SAGCM-APD). This improvement is obtained by adding a new thin charge layer between absorption and grading layers, with assuming the non-uniform electric field in different regions of the structure. In addition, a circuit model of the proposed structure is extracted, using carrier rate equations. Also, to achieve the optimum structure, it is tried to have trade-offs among thickness of the layers and have proper tuning of physical parameters. Eventually, frequency and transient response are investigated and it is shown that, in comparison with the previous conventional structure, significant improvements in gain-bandwidth product, speed and also in breakdown voltage are attained.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Laser self-mixing interferometer for MEMS dynamic measurement
Zhaoyun ZHANG, Yang GAO, Wei SU
Front Optoelec. 2013, 6 (2): 210-215.
https://doi.org/10.1007/s12200-013-0318-x
Laser self-mixing interferometer has the advantages of simple architecture, compact size, naturally self-aligned optical characteristics, and low cost. It is promising to replace conventional interferometers for physical measurements, such as displacement, distance, velocity, vibration, and so on. In this paper, this interferometer was tried to be used for micro-electro-mechanical system (MEMS) dynamic measurement. Firstly, its measurement principle based on a three-mirror cavity model was presented, and then the laser self-mixing interferometer for MEMS dynamic measurement was designed, experiments were finally performed as target moves with different forms. Experimental results suggest that self-mixing interferometer is available for MEMS dynamic measurement, and may have wider applications in the future.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Particle size regression correction for NIR spectrum based on the relationship between absorbance and particle size
Jinrui MI, Luda ZHANG, Longlian ZHAO, Junhui LI
Front Optoelec. 2013, 6 (2): 216-223.
https://doi.org/10.1007/s12200-013-0320-3
Based on the effect of sample size on the near-infrared (NIR) spectrum, the absorbance (log(R)) in any wavelength is divided into two parts, and one of them is defined as non-particle-size-related spectrometry (nPRS) because it is not influenced by particle size. To study the relationship between the absorbance and particle size, the experiment material including nine samples with different particle size was used. According to the regression analysis, the relationship was studied as the reciprocal regression model, y = a + bx + c/x. Meanwhile, the model divides absorbance into two parts, one of them forms nPRS. According to the nPRS, a new correction method, particle size regression correction (PRC) was introduced. In discriminate analysis, the spectra from three different samples (rice, glutinous rice and sago), pretreated by PRC, could be directly and accurately distinguished by principal component analysis (PCA), while by the traditional correction method, such as multiplicative signal correction (MSC) and standard normal variate (SNV), could not do that.
Figures and Tables |
References |
Related Articles |
Metrics
|
|
Improved photovoltaic properties of Si quantum dots/SiC multilayers-based heterojunction solar cells by reducing tunneling barrier thickness
Yun-Qing CAO, Xin XU, Shu-Xin LI, Wei LI, Jun XU, Kunji CHEN
Front Optoelec. 2013, 6 (2): 228-233.
https://doi.org/10.1007/s12200-013-0324-z
Si quantum dots (Si QDs)/SiC multilayers were fabricated by annealing hydrogenated amorphous Si/SiC stacked structures prepared in plasma enhanced chemical vapor deposition (PECVD) system. The microstructures were examined by transmission electron microscopy (TEM) and Raman spectroscopy, and results demonstrate the formation of Si QDs. Moreover, p-i-n devices containing Si QDs/SiC multilayers were fabricated, and their photovoltaic property was investigated. It was found that these devices show the good spectral response in a wide wavelength range (400–1200 nm). And it was also observed that by reducing the thickness of SiC layer from 4 to 2 nm, the external quantum efficiency was obviously enhanced and the short circuit current density (Jsc) was increased from 17.5 to 28.3 mA/cm2, indicating the collection efficiency of photo-generated carriers was improved due to the reduced SiC barriers.
Figures and Tables |
References |
Related Articles |
Metrics
|
16 articles
|