Spatial Self-phase Modulation Effect Of C₆₀ Toluene Solution And Its Application

With the rapid development of economy and society,human beings are increasingly demanding the acquisition,storage,processing,and distribution of information.A wide variety of optoelectronic devices are the cornerstone of the modern information society.The nonlinear optical effects have received wide attentions because of their important applications in optoelectronic devices.Nonlinear optics belongs to the realm of the interaction between light and matter.It studies the phenomenon of the nonlinear relationship between the stimulation of light on matter and the response of matter to light.Optical nonlinearity can only be manifested when the light intensity is large enough.Among them,the spatial self-phase modulation effect is an important kind of nonlinear optics effect,which arises from the spatially variable refractive index distribution in the medium induced by intense laser.The spatially varying refractive index affects the light beam propagating in the medium.The diffraction pattern of concentric rings,i.e.a self-diffraction ring,is produced in the far-field observational plane.The spatial self-phase modulation effect widely exists in various materials.The nano-carbon material represented by C₆₀0 has become a research focus due to its unique advantages.In this thesis,the spatial self-phase modulation effect of C₆₀ toluene solution and its applications are presented.The main innovations of this thesis are as follows:the factors affecting the spatial self-phase modulation effect of C₆₀ toluene solution are studied.With the aid of closed-aperture Z-scan measurements to C₆₀ toluene solution,third-order local nonlinear refraction and thermally induced nonlocal nonlinear refraction are identified and quantitatively separated.The research content of this thesis includes:1.The effect of gravity on the spatial self-phase modulation effect of C₆₀ toluene solution is investigated.It is determined that gravity is the cause of distortion of the self-diffraction rings.The characteristic times required for formation and distortion of the self-diffraction rings are measured.The modified experimental set-up for avoiding distortion of self-diffraction rings is presented.The influences of both sample concentration and laser wavelength on the spatial self-phase modulation effect of C₆₀ toluene solution are studied.It is shown that the number and radius of self-diffracting rings are positively correlated with the sample concentration.Moreover,the pattern of self-diffraction rings is sensitive to the laser wavelength.It is determined the optimum concentration and the optimal wavelength for observing the self-diffraction rings.The influences of laser intensity and sample thickness on the spatial self-phase modulation effect of C₆₀ toluene solution are studied.It is found that the number and the radius of self-diffracting rings are positively correlated with the laser intensity and sample thickness.Interestingly,at relatively high intensity,the dependence of number of rings on intensity has a saturation effect.2.By modeling a mathematical description of coexistence of local and nonlocal nonlinear refraction effects,a method for identifying and separating local and nonlocal nonlinear refraction effects is proposed.Under the condition of simultaneous third-order local and thermally induced nonlocal nonlinear refraction,the thesis gives analytical expressions of?i?closed-aperture Z-scan normalized transmittance and?ii?the number of self-diffraction rings versus light intensity in spatial self-phase modulation effect.The identification and separation of the third-order local nonlinear refraction and the thermally induced nonlocal nonlinear refraction of C₆₀ toluene solution are performed by closed-aperture Z-scan experiments and spatial self-phase modulation experiments at two different wavelengths.