Research On Lasing Method Of Fiber-type Microcavity Laser With Coherent Feedback

Fiber-type microcavity laser is a new type of laser that combines optical microfluidic or micromachining technologies to introduce gain and resonance mechanisms into fibertype structures to form lasing.In traditional microcavity lasers or random lasers,the former provides feedback for laser oscillation through the regular cavity itself or specular reflection;the latter provides multiple scattering and positive feedback by the disordered medium.In the fiber-type microcavity laser,due to its own defects(material defects/artificially designed defects),lasing is usually formed under the combined action of the cavity and the disordered scattering medium.The structure and output characteristics of this type of laser are different from the above two lasers.Its unique structure can realize the confinement and regulation of light,and has been gradually applied in the fields of sensing,imaging and information encryption.However,due to the complex influence of cavity and scattering medium on laser formation,in order to explore the role of the two in the laser formation process,this thesis studies the influence of the cavity and scattering medium on the lasing mode from simulation and experiment by making a fiber-type disordered microcavity laser and a fiber-type whispering gallery mode(WGM)microcavity laser.In the first part,thesis proposes a single-pulse spectral synchronization and encoding method of coherent random lasers using laser injection methods.In terms of laser design,the disordered scattering layer introduced into the inner wall of the hollow core fiber,on the one hand,realizes the confinement of the formed laser brought by the microcavity,and on the other hand provides disordered feedback as a scattering medium to form a coherent random lasing mode.The effects of different scattering particle concentrations and refractive index changes on the confined light field and the formation of random laser modes are obtained through simulation analysis.On this basis,a multi-peaks coherent random laser is realized by fabricating experimental samples.Then,the concept of network node is introduced to regard the laser as a node,and the single-pulse synchronization between master and slave nodes(between different disordered microcavity lasers)is realized firstly through multimode fiber cascading nodes,revealing the synchronization conditions and laws between disordered microcavity lasers.Finally,a key generation and sharing method between synchronization nodes is proposed by utilizing the unclonability properties of laser spectra.In the second part,thesis proposes and realizes a scattering-enhanced fiber-type WGM laser with logic state characteristics.By filling the fiber-type WGM microcavity with liquid crystal dyes and utilizing the light confinement of the WGM microcavity and the scattering of the light by the liquid crystal molecules,the axial output of the WGM laser with enhanced scattering is realized.The theoretical and experimental results show that the scattering of liquid crystal molecules can couple part of the fluorescence of the liquid core into the WGM mode to promote the laser emission,and also enhance the axial coupling efficiency of the WGM laser.Further combined with the hysteresis mechanism of liquid crystal molecules,a bistable laser output was obtained.The orientation of the liquid crystal molecules was controlled by voltage and temperature to change the scattering characteristics,and the spectral and intensity characteristics of the output were regulated.Finally,it is proposed to define and control the logic state "1-0/bright-dark" by using the realized laser bistable characteristic,which provides a reference value for the logic control of the liquid logic state laser.