Nonlinear Optical Effects Of Two-dimensional Bi₂S₃ And Their Applications In All-optical Devices

Since graphene was discovered,it has attracted more and more scientists’attention,furthermore,there are more and more new two-dimensional materials were found,due to its excellent properties.Some two-dimensional nanomaterials have excellent performance in the fields of physics and chemistry.The two-dimensional semiconductor nanomaterial bismuth sulfide（Bi₂S₃）used in this article perform well in physics and it has good optical response to different light with various wavelengths.It can be applied to the design of a variety of optoelectronic devices,such as all-optical switches,all-optical information Transmission devices,all-light diodes,thermoelectric coolers,electrical switches,etc.However,there is little report on the non-linear effects of bismuth sulfide.In this paper,we explore the non-linear effect of bismuth sulfide with three different wavelengths of light,and design all-optical devices based on this.The results obtained are as follows:（1）We researched the micro-morphology of bismuth sulfide and took a micro-morphological picture.Based on the optical Kerr effect,we measured its nonlinear refractive index（9）₂)using self-phase modulation technology,and studied the relationship between its nonlinear optical effect and incident light intensity.For different wavelengths of incident light,its optical response is different,and the number of diffraction rings formed is also different.Due to the effects of gravity and thermal effects,the diffraction ring will collapse.We measured the degree of collapse and used formulas to prove the relationship between the collapse effect and the change in nonlinear refractive index.For laser of the same wavelength,the degree of collapse is related to the incident light intensity,but it is not linearly.（2）On the basis of self-phase modulation,we introduce a strong light and a weak light,taking advantage of the cross-phase modulation to design an all-optical switch.In this device,strong light is used as the switching light to modulate the phase of the weak light to achieve control of the weak light.When the controlling light is turned on,the signal light occur the non-linear effect;when the control light is turned off,the signal light has no the non-linear effect.In this way,we achieved the function of all-optical switches by controlling two beams of light.Because of the modulation characteristics of the all-optical switch,we have designed an all-optical information transmission device,and we can control the output of the signal light by controlling the input of the switching light.We record the non-linear effect as"1",on the contrary regard it as"0",so that we can achieve the output of 0 and 1 by controlling the switching light,and then translate the specific information into digital information.The message can be passed.（3）Bismuth sulfide is a narrow-band saturable absorption material with a wide spectral response range.As long as the intensity of the light is sufficient,its nonlinear effect can be excited,and a diffraction ring appears.We designed an all-optical diode device using a combination of selenium sulfide（Sn S₂）and bismuth sulfide,and Sn S₂have opposite properties to bismuth sulfide.Selenium sulfide is a broadband anti-saturation absorbing material.It can be designed as an all-optical diode with a heterojunction combined with bismuth sulfide to achieve a unidirectional light path.