Study On Wideband All-optical Modulation Based On SnSe Coated Microfiber-knot Resonator

With the arrival of optical communication era,optical fiber sensing and detector components have become one of the important integrated optics,and optic fiber knot resonator based on microfiber(MF)also attracted much attention.Due to the advantages of compact structure,good resonance effect and strong evanescent field,Micro-knot resonator(MKR)is widely used in fiber lasers,filters and fiber sensors,etc.Tin selenide(SnSe),as a two-dimensional transition metal dichalcogenides(TMDs)material with graphene-like layered structure,has excellent optical and thermoelectric properties,which makes it used in various photoelectric devices.In this paper,combined with the advantages of micro-knot resonator and tin selenide,the light modulator is realized under the interaction of MKR strong evanescent field and SnSe light absorption.The optical-control characteristics and modulation response time of the device are discussed.In the experiment,SnSe nanosheet dispersion is covered on the surface of the microfiber knot by physical deposition,and the light controllable characteristics of device based on SnSe-MKR structure were measured under four kinds of external pumping light: under the 405 nm violet light,532 nm green light,660 nm red light and 808 nm near-infrared light,the maximum relative change of the optical transmitted power of device was about 11.8 dB,13.5 dB,12.9 dB and 6.7 dB,respectively.The corresponding maximum modulation sensitivity was about 0.594 dB/mW,0.352 dB/mW,0.356 dB/mW and 0.158 dB/mW.And on this basis the modulation response time of device are measured: under 405 nm violet light,532 nm green light,660 nm red light and 808 nm near-infrared light,the rise/fall response time was 1.9 ms/1.9 ms,2.0 ms/1.6 ms,1.9 ms/1.8 ms and 1.9 ms/1.6 ms,respectively.Further analysis shows that at the resonance wavelength where the extinction ratio is lager in the transmission spectrum,the Q value is also lager.The greater relative change in the transmitted optical power,the higher modulation sensitivity.Compared the experimental results with related performance parameters of the optical modulator,proves that the unique property of this structure.Based on coupled mode theory,MATLAB software is used to fitting the transmission spectrum of the microfiber knot before and after deposition SnSe nanosheet.The fitting results have good match with the experimental data,verified the accuracy of experimental results.The physical model established by the COMSOL simulation software is used to analyze the mode field distribution of SnSe-MKR waveguide composite structure under the external light pump,and the light absorption characteristics of SnSe material are proved.In addition,the optical control theory and modulation characteristics are explained and analyzed in details.The innovations of this work are as follows:1.A fiber-optic modulator based on 2D SnSe and MKR is proposed to realize modulates the 100 nm(1520?1620 nm)wide spectrum signal under the action of 405 nm/532 nm/660 nm/808 nm wide band pumping light.2.The modulation characteristics and theory of the device are theoretically explained by coupling mode theory and light absorption theory.The relationship between modulation performance and Q value,extinction ratio is also studied.