Q-switched 2?m Lasers Based On Low Dimension Nanomaterials As Saturable Absorbers

Q-switched nanosecond pulsed lasers operating at 2 p,m wavelength have important applications in many fields,such as medical,communication,military,processing and manufacturing and so on.There are two Q-switch techniques,including acive Q-switching achieved by the acousto-optic(or electro-optic)effect of some certain crystals,and passive Q-switching realized by saturable absorber,such as Cr:YAG,GaAs,graphene and so on.Compared with active Q-switching devices,saturable absorbors based on lwo dimension nanomaterials are more in line with the requirements of integrated laser with advantages of low cost,compact structure and so on.In this thesis,we mainly study on 2 ?m passively Q-switched laser operation in LD pumped Tm:YAP laser based on MoS2-black phosphorus composite and liquid metal galinstan nanosphere.The details as follows:1.The introduction part briefly reviews the development of 2 ?m laser technology and its application in various fields,and introduces the level structure and superiorities of LD pumped Tm:YAP laser.Besides,we also introduce the principle and method of active and passive Q-switching,and research the relative merits of various frequently-used passive Q-switch and previous representative works.Then,we detailed the optical properties of MoS2,black phosphorus and surface plasmon nanomaterials,as well as their research advances in 2 ?m passive Q-switching.2.The mechanism of saturation absorption is described from the dynamic process and nonlinear optics.The formula of saturable absorption coefficient with the change of optical intensity is derived in the two-level system,and the third-order nonlinear absorption coefficient is also derived by basic nonlinear optics principle.Then,the process of passive Q-switching and the role of saturable absorber are described from cavity gain and loss.3.In this part,we respectively test the performance of MoS2-BP composite as a saturable absorber in a passively Q-switched Tm:YAP laser.Firstly,we introduce several common used preparation methods of 2D materials and their merits and demerits,and the preparation process of our samples by liquid phase exfoliation method.Secondly,some frequently-used characterization technique of 2D materials and characterization results of our samples are introduced,including micro-morphology,Raman spectra,and both linear and nonlinear optical absorption.Then,the performance of MoS2,BP and their composite as passive Q-switch in an all-solid Tm:YAP laser are studied and discussed,respectively.4.The main content of this part is liquid metal galinstan saturable absorber based 2 ?m passively Q-switched laser.We first introduce the process of ultrasonic preparation of liquid metal nanosphere sample,then exhibit characterization results of our prepared sample,including micro-morphology,linear absorption of different ultrasonic time and nonlinear absorption property.Then we show experimental results and discussion of passively Q-switched laser operation at 2 ?m and 1.3 ?m based our liquid metal sample.