Study Of SHG On PbO-B₂O₃ Glasses And P-N Junction Amorphous Silicon Thin Films

It has been evoking widespread interests for the nonlinear optical materials own extensive uses in the fields of optical information technology, laser frequency conversion technology, laser transmission technology, laser protection technology, material structure analysis and so on. Glass is used as a nonlinear optical materials, it has wide transmission range, preferable chemical stability and thermal stability, higher light damage threshold value, larger nonlinear optical susceptibility, fast response time, the ease of achieving fiber or thin films, and lower cost. However, the mechanism for second harmonic generation (SHG) of glass is uncertain, how to improve the second-order nonlinear coefficient which is important parameter for its application is a key topic.The homogeneous PbO-B₂O₃ glasses were prepared by conventional melt quenching technique by controlling the melt crafts. Utilizing the techniques such as X-Ray diffraction, Raman spectra, UV-Vis spectra, thermally stimulated depolarization current (TSDC) technique, HF etching technique, and so on, the structure and performance of PbO-B₂O₃ glasses after thermal/electric poling, the mechanism of SHG, and the dependence SH intensity on the chemical composition or poling parameters have been researched.The mechanism for thermally induced SHG in PbO-B₂O₃ glasses was studied. The results showed that stress gradient was responsible for the SHG from the relation of cooling process or inner properties and SH intensities.Based on the depletion layer theoretical model, SHG has been researched in the plasma-deposited P-N junction hydrogenated amorphous silicon thin films. The results showed that the existence of built-in electrostatic fields in P-N junction amorphous silicon thin films is the origin of second-order nonlinearity, considering no SH signals was detected in P type or N type amorphous silicon thin films and SHG was observed in P-N junction amorphous silicon thin films. It is proved in theory. Utilizing quartz crystal as reference, the second-order nonlinear susceptibility was calculated according to the bulk formula and thin films formula. The calculated coefficient was compared with the current research situation.In conclusion, thermally induced SHG, as a new method to induce SHG, is to enrich the nonlinear optical theory. However, the SH intensities of thermally induced PbO-B₂O₃ glasses is lower than those of thermal/electric poling. For P-N junction amorphous silicon thin films, larger nonlinear optical susceptibility is obtained and is easily changed into optical devices, it will be of important interest.