| Low-dimensional nonlinear materials is a very important role in the integration and miniaturization of optoelectronic devices and all-optical devices.In recent years,As an important CMOS process compatible material,The changes of atomic composition and structure of the silicon nitride can significantly affect its third-order nonlinear response.It has become one of the research hotspots in this field.There are many traditional methods for preparing silicon nitride films.SiN was most commonly grown by the chemical vapor deposition?CVD?technique.However,CVD has some drawbacks in the preparation of SiN films.For example,the growth temperature is usually high,which makes the integration with the other CMOS materials to form an all-optical or optoelectronic device challenging;the hydrogen content is significantly increased in the deposited SiN film.leading to the non-intrinsic and unstable optical nonlinearity from SiN.Physical vapor deposition?PVD?techniques such as radio-frequency?RF?magnetron sputtering using a ceramic Si3N4 target proves to be a viable alternative approach to overcome the drawbacks from CVD.The third-order optical nonlinearity in such SiN film prepared by RF-sputtering has seldom been investigated.In this article,we report the third-order optical nonlinearities in SiN films which were prepared using RF magnetron sputtering at room temperature?RT?,and further annealed under argon?Ar?and Oxygen?O2?,respectively.The nonlinear refractive index n2 and absorption coefficient?in the samples were determined using Z-scan method at near-infrared wavelength1064 nm.The value of n2 in the SiN prepared at RT was determined,which is three orders of magnitude larger than that in SiN films prepared by CVD method.The further enhanced n2,while the relatively unchanged?in SiN films,thus the enhanced ratio of|Re??3?|/|Im??3?|were obtained in the annealed films,where Re??3?and Im??3?are real and imaginary parts of third-order nonlinear susceptibility??3?,respectively.The optical bistability in SiN resonant waveguide grating was numerically studied.The low threshold intensity around 300 MW/cm2for the RWG was obtained.The main contents of this paper are summarized as follows:1.Firstly,we introduce the research background and current status of silicon nitride materials,as well as the research background and application prospects of nonlinear optics.The Z-scan technique used in the experiment was introduced,And we give the theoretical calculation formula of the third-order nonlinear refractive index and saturated absorption coefficient.2.We briefly introduce the common methods of preparing silicon nitride films,After comparison,we finally used magnetron sputtering to prepare SiN film,and we gave the sputtering parameters.Secondly,through the EDS characterization of the target,it is proved that the Si/N element ratio of the target is consistent with the theoretical value of 3/4.Finally SiN films were prepared at room temperature?RT?,and further annealed at a low temperature200°C and a relatively high temperature 600°C under argon?Ar?.The structural changes of the annealed SiN film were analyzed by AFM,SEM,transmittance and other methods,and then we discussed the changes of the third-order nonlinear coefficient and saturation absorption coefficient of the silicon nitride film at different temperatures.3.We not only anneal the SiN prepared at room temperature under an argon atmosphere,but also annealed it under an oxygen atmosphere,and the annealing temperature is 200 degrees low temperature and 600 degrees high temperature.Through AFM,transmittance and other methods,we confirmed the change in the appearance of the sample after annealing.And took a series of elemental analysis by EDS method,we found that the ratio of oxygen-containing elements of the sample after annealing was increased.At the same time,we also discussed the variation of the third-order nonlinear coefficient of the silicon nitride film annealed in an oxygen atmosphere.4.We were simulated using the finite element method studied the optical bistability in SiN resonant waveguide grating.The low threshold intensity around 300 MW/cm2 for the RWG fabricated by the annealed SiN film under Ar was obtained... |
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