Studies Of The Electric-filed-induced And Stress-induce Second-order Nonlinear Optical Effects In Silicon

As a main material in micro-electronics silicon has its advantageous in production cost and processing technic.However an ideal silicon crystal does not possess linear electro-optical effect because it has inversion symmetry centre. We cannot use silicon to make into high-speed silicon electro-optic modulators and optical switches. In recent years, we have obtained the successful development of silicon-based electro-optic modulations which are based on plasma dispersion effect.In this thesis, the dc electric field and stress is used for breaking the inversion symmetry of silicon, as a result, the electric-field-induced linear electro-optical effect and optical rectification occur in silicon, and these effects are researched theoretically and experimentally. We have also distinguished influence on electro-optical signal between linear electro-optical effect and plasma dispersion effect .Based on this effect of electro-optic modulator can not change just because the disadvantages, for example, carrier lifetime, drift and diffusion and other factors, can not achieve high modulation speed. While on the electro-optic modulator has been optimized to greatly enhance the modulation speed, but based on this mechanism of electro-optic modulator, or significantly less than the speed of the linear electro-optic effect in silicon-based electro-optic modulator, and based on plasma dispersion effect of optical modulator structure and electrical sector is complex.In this thesis, using electric field and strain field damage silicon inversion symmetry, it has the electric field and stress-induced linear electro-optic effect and optical rectification effect. Thesis of silicon materials for the linear electro-optic effect of field effect and optical rectification carried out theoretical and experimental study, and analyzes the distinction between the linear electro-optic effect and the plasma dispersion effect on the electro-optic signal of.Ⅰ.Studies of electric-field-induced linear electro-optical effectWe have focused on the external electric field on silicon linear electro-optic effect.⑴We derive when the external electric field and stress are along the [111] direction acting on the silicon material, the point group symmetry of silicon will be reduced from to , thus silicon will have the electric field and stress-induced nonlinear optical effects. The equivalent second-order nonlinear susceptibility tensor is equal to third-order nonlinear susceptibility tensor and the dot product of electric field and stress,that is⑵We analyzed the frequency exist in the same silicon electric field, electric field, electric field polarization waves the expression, further change the refractive index formula is derived. We then according to the refractive index ellipsoid and the electro-optic tensor strain tensor related knowledge, experimental design verification of our theoretical analysis.⑶We use the silicon material is along the (111) cut.The electric field and electric field modulation at the same time added to the sample, field observations to significantly enhance the linear electro-optic effect.Ⅱ. Field effect of optical rectification⑴A pplication of nonlinear optics knowledge,we analysis when the electric field along the [111] direction, the field size of optical rectification signal the relationship between the incident polarization azimuth.⑵We use the sample is nearly intrinsic silicon, cutting direction along [111], Metal - insulator - semiconductor - insulator - metal sample structure. We observed that the built-in electric field induced optical rectification signal Field. The experiment showed that externally applied electrical field can enhance the field induced optical rectification signal. This is equivalent to our previous studies, second-order nonlinear susceptibility tensor is proportional to conform with the electric field.ⅢDistinguish between the linear electro-optic effect with the plasma dispersion effect.We first use of transverse electro-optic modulation system, measuring the output of the electro-optic signal. According to the research on the Jones matrix derived the specific form of the output light intensity. As the linear electro-optic effect of the applied electric field causes the phase delay associated, the plasma dispersion effect is only associated with the carrier concentration, therefore, the change of the output light intensity can distinguish between the two.The above study has an important role, in silicon integrated optics, and many other areas that will play a great prospect. Methods and results of these studies to other materials with inversion symmetry the nonlinear study has important reference value.