Q-switched Erbium-doped Fiber Laser Based On Iron Oxides

The birth of the first ruby laser in 1960 marked a new youth of optics and with the development of low-loss fiber fabrication technique,fiber laser has attracted a huge research interest due to its remarkable advantages,such as cost-effective,great stability,good quality of laser beams,low starting threshold,high efficiency of transition from electronic to photonic,unnecessary water-cooling system,great gain feature and the compatibility with optical fiber communication system.Since the Noble Prize went to graphene in 2010,low dimensional materials have been investigated with considerable attention by physics and chemists all over the world.In the field of fiber laser,passively Q-switched and mode-locked laser are successfully achieved by using saturable absorbers(SAs)which are based on the low dimensional materials.Thus the research of low dimensional materials has been a hot spot in recent years.A numerous type of low dimensional materials have been demonstrated to exhibit saturable absorption property,such as zero-dimensional materials like quantum dots,one-dimensional materials like carbon nanotube or gold rod,two-dimensional materials like graphene,black phosphorus,transition metal dichalcogenides(such as WS₂,WSe₂,ReS₂,Mo Se₂,Mo S₂,WTe₂,Mo Te₂,etc.).In this thesis,two type of iron oxides(Fe₃O₄ and Fe₂O₃)nanoparticles are fabricated by a co-precipitation method and two saturable absorbers based on the nanoparticles are fabricated and characterized,and after respectively inserting the saturable absorber into an erbium-doped fiber laser,passively Q-switched operations are obtained.In addition,further properties of the laser are investigated in detail.The main content of this thesis is as follows:1.Fe₃O₄ nanoparticles are characterized firstly.Then by mixing polyvinyl alcohol(PVA)solution with the nanoparticles and evaporating them on a slide,the Fe₃O₄-PVA film is prepared as SA and its linear and nonlinear optical properties are studied.After inserting the SA to an erbium-doped fiber laser,passively Q-switched operation is obtained and then analyzed.After mixing polyimide(PI)solution with Fe₃O₄ nanoparticles and then evaporating them on a slide,a Fe₃O₄-PI film is also fabricated as a comparison with Fe₃O₄-PVA film.The optical properties of the Fe₃O₄-PI film are investigated and Q-switched operations are also achieved in the erbium-doped fiber laser based on this SA.In addition,it is found that the damage threshold and the stability of the laser under high pump power can be optimized by changing the basal material.2.Fe₂O₃ nanoparticles are fabricated by a co-precipitation method and also characterized.By using the same method,the Fe₂O₃-PVA film is then prepared and its linear and nonlinear optical properties are studied.After incorporating the Fe₂O₃-PVA SA with the erbium-doped fiber laser,Q-switched laser pulses are generated.Moreover,by utilizing a tapered fiber as the mode converter,a two-mode fiber Bragg grating as the mode selector and the Fe₂O₃-PVA film as the SA,a passively Q-switched vector beam erbium-doped fiber laser is achieved,indicating that the Fe₂O₃ nanoparticles exhibit a polarization-insensitive property.3.ReS₂ nanosheets are prepared by a liquid exfoliation method and then characterized.Equally to the method used in fabricating iron oxides based SAs,a ReS₂-PVA film is subsequently made and characterized.Then both passively mode-locked and Q-switched laser are achieved in an erbium-doped fiber laser by using the ReS₂-PVA film.As a comparison to the iron oxides,it is found that only Q-switched operations can be realized in the erbium-doped fiber laser when utilizing Fe₂O₃-PVA film as the SA and this phenomenon is discussed in detail.