Research On Interferometric All-fiber Modulator Based On Microfiber

With the development of optical communication technology and optical fiber sensing technology,optical modulators play an important role in photonics and optoelectronics.At present,there are many problems in optical modulators such as large device size,complicated system,poor stability,and low accuracy,and are difficult to integrate with existing photovoltaic systems.Therefore,the miniaturization and integration of devices is a research hotspot of optical modulators.In addition,micro-nano-scale optical waveguides are an inevitable trend in the development of photonic devices.As a new type of optical waveguide,microfiber have the advantages of evanescent field strength,low loss,simple preparation,flexible design and good flexibility,besides the general function of optical waveguides.Moreover,the microfiber can be easily coupled with the standard fiber in various ways,and has a high coupling efficiency,which can reduce the optical power requirement of the laser.Therefore,the structurally integrated all-fiber modulation device can be prepared by utilizing the structural characteristics of the microfiber and combining the optical characteristics of various optical functional materials.In this thesis,the Mach-Zehnder integrated optical fiber modulator based on two different materials was studied by combining tapered microfiber and optical functional materials,and its performance is studied experimentally.At the same time,the modulation mechanism is analyzed theoretically,this research is of great significance for exploring the structure of all-fiber integrated optical fiber modulator.In this thesis,an optical fiber interferometric modulator based on ionic liquid electro-optic effect and an optical fiber interferometric modulator based on Au nanorod photo-thermal effect are experimentally explored.Light modulation is realized by the combination of tapered microfiber and functional materials.Among them,the tapered microfiber is a symmetrical non-adiabatic double-cone micro-nano structure,which can be prepared by flame heating and melting taper method.Based on the fiber interferometric structure,the modulation characteristics of the ionic liquid integrated tapered microfiber modulator were studied firstly.Because of the electro-optic effect,the refractive index of the ionic liquid changes under the action of voltage,and the modulation effect of the electro-optic modulator was tested.The wavelength modulation of the interferometric spectrum and the light intensity modulation of the fixed wavelength are realized,the wavelength modulation range is up to 6.1 nm and a light intensity variation of is 9.8 dBm.Then,the Au nanorod integrated tapered microfiber modulator is studied.The Au nanorod produces a photo-thermal effect under the action of the near-infrared excitation light at 808 nm.The refractive index of the medium changes with the increase of temperature,and the wavelength modulation of the interference spectrum and the intensity modulation of the fixed wavelength are also realized.The maximum wavelength modulation amplitude is 3.3 nm.With a single wavelength tracking of 1548 nm,the modulation depth can reach 45.1 %.The above two kinds of optical modulators based on microfiber have the characteristics of high integration,compact structure and fast response speed,which have potential application value in the fields of optical switches,electro-optical modulators,and all-optical modulators.