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Nonlinear dynamics of 1550 nm VCSELs subject to polarization-preserved optical feedback and orthogonal optical injection
Bin WEI, Zhengmao WU, Tao DENG, Guangqiong XIA
Front Optoelec. 2013, 6 (3): 243-250.
https://doi.org/10.1007/s12200-013-0333-y
Based on spin-flip model (SFM), the nonlinear dynamics of 1550 nm vertical-cavity surface-emitting lasers (VCSELs) subject to polarization-preserved optical feedback (PPOF) and orthogonal optical injection (OOI) are theoretically investigated. The results show that two linear polarization (LP) modes can be simultaneously stimulated and polarization switching (PS) can be observed, which is different from the case that only y LP mode exists in a VCSEL with PPOF. Under the joint action of PPOF and OOI, the two LP modes will exhibit rich dynamical states, such as period one, period two, multi-period and chaos oscillation. Different evolution routes to chaos can be also observed. Moreover, frequency detuning Δf (Δf = fm - fs, where fm and fs are the center frequencies of free-running master VCSEL and slave VCSEL, respectively) has an obvious influence on the PS. With the increase of the positive frequency detuning PS points shift toward larger injection strengths; meanwhile, a suitable negative frequency detuning value makes the injection strength for PS be the lowest.
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Investigation on layover imaging in synthetic aperture ladar
Zhaosheng YANG, Jin WU, Zhilong ZHAO, Donglei WANG, Yuanyuan SU, Na LIANG
Front Optoelec. 2013, 6 (3): 251-260.
https://doi.org/10.1007/s12200-013-0358-2
Due to the short laser wavelength, almost all practical targets are rough. Surface elevations in rough targets will result in layovers in synthetic aperture ladar (SAL). High resolution SAL image with layovers will be different from the target picture taken by incoherent tools as digital camera. To investigate the layovers in SAL image, a simplified mathematical model is built by optics diffraction theory and a laboratory SAL is setup using 1550 nm tunable laser source. Layovers in SAL images, in both theoretical simulation and experimental demonstration, are carefully observed. Detailed results on various targets are illustrated.
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Influence of substrate temperature on in situ-textured ZnO thin films grown by MOCVD
Yajuan ZHENG, Xiangbin ZENG, Xiaohu SUN, Diqiu HUANG
Front Optoelec. 2013, 6 (3): 270-274.
https://doi.org/10.1007/s12200-013-0326-x
The influence of substrate temperature on microstructure, electrical and optical properties of in situ-textured zinc oxide (ZnO) films fabricated by metal organic chemical vapor deposition (MOVCD) had been investigated. Results indicated that the substrate temperature played a very important role on preparation of ZnO thin film. With the raising of temperature, firstly ZnO crystals were perpendicular to the substrate, then they were grown inclining toward the substrate, finally ZnO crystals grown in layers but not regular. Consequently, ZnO film surface morphology changed from smooth to a pyramid structure and then disappeared little by little. Moreover, it was also found in this study that ZnO film was characterized with high crystallinity, low resistivity (2.17 × 10-2) and high transmittance (>80%). These results suggested that ZnO thin film is suitable for front electrode of silicon thin film solar cell.
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Design optimization of microwave properties for polymer electro-optic modulator using full vectorial finite element method
Kambiz ABEDI, Habib VAHIDI
Front Optoelec. 2013, 6 (3): 290-296.
https://doi.org/10.1007/s12200-013-0335-9
In this paper, a polymer electro-optic modulator has been designed and optimized using the full vectorial finite element method. For this purpose, the effects of magnesium oxide (MgO) and down cladding thicknesses, distance between two ground electrodes, hot electrode and modulator widths modulator on the key modulator parameters, such as microwave effective index nm, the characteristic impedance ZC and the microwave losses α are presented. After selecting optimal dimensions of polymer electro-optic modulator, frequency dependent aforementioned parameters and the half-wave voltage-length product (VπL) parameter of polymer electro-optic modulator are extracted and as a consequence, an optimized design is reported. Finally, the optical and electrical modulation responses of polymer electro-optic modulator are calculated. The optimized polymer electro-optic modulator exhibits 3-dB electrical bandwidth of 260 GHz and VπL about 2.8 V?cm in this frequency.
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