| Summary: | 碩士 === 國立中山大學 === 通訊工程研究所 === 94 === Blue/Green lasers can be applied in a wide range such as high-density optical storage, display, biomedical analysis and under water communications. C-band wavelength conversion is one of the most key technologies in DWDM system. Optical Wavelength converter using nonlinear effect can provide high transparency, subcarrier-multiplexed channels and can be fused easily and directly with optical fiber. These characteristics have more advantages than those of O/E/O methods.
In this thesis, periodically poled LiNbO3 (PPLN) crystal fiber for wavelength conversion is grown by LHPG method with high-electric-field bias. The relationship between the polarization inversion and micro-swing is analyzed. For different applications, PPLN crystal fiber need appropriate pitches of polarization inversion to meet quasi phase matching. For example, domain period of 15.45 um is used for tunable blue/green lasers. By means of cascaded SHG/SFG effect, when fundamental power is 100 mW, the internal conversion efficiency of SHG and cascaded SHG/SFG were -9.2 dB and -31.9 dB respectively. The SHG 3-dB bandwidth is 9 nm. While the domain pitch varies from 16.79 um to 25.79 um with 30 nm periodic increment , the simulation shows that the cascaded SHG/SFG 3-dB bandwidth is 65 nm in the range of 1476-1672 nm for fundamental wavelength. Domain period of 18.9 um is used for C-band wavelength converter. By means of cascaded SHG/DFG effect, when the crystal length is 1.8 mm, the effective nonlinear coefficient is 18.2 pm/V, which is 83 % of theoretical value. Conversion efficiency is about -59.3 dB when fundamental power and signal power were 350 mW and 15 mW, respectively.
|
|---|
