Study On The Application Of Two-dimensional Transition Metal Disulfide In Signal Modulation Of Fiber Laser

Passively Q-switched and passively mode-locked fiber lasers are pulsed fiber lasers that use Q-switched or mode-locked technology to convert continuous laser output into pulsed laser output.Passively Q-switched and passively mode-locked fiber lasers do not require external modulators and power modules,making the entire laser system highly integrated and small in size.Therefore,more and more attention has been paid to the research of passively Q-switched and passively mode-locked fiber lasers.Saturable absorber is an important part of passive Q-switched and mode-locked fiber lasers,and it is the core of obtaining pulsed laser output.A saturable absorber with excellent performance has the effect of"passing strong light and blocking weak light".This"strong light and weak light"refers to the intensity of the laser light field is such that a laser with a certain intensity will bleach the saturable absorber without loss,and a laser with a weak intensity will be largely lost.Semiconductor saturable absorber mirror(SESAM)is a saturable absorber element with relatively mature technology on the market and a very wide range of applications.According to the regulation of process parameters,it can achieve pulsed laser output from nanoseconds to femtoseconds in fiber lasers.It is stable,but SESAM also has certain shortcomings.The working wavelength range of SESAM is narrow,and generally it can only work in a certain wavelength range.In addition,the production process of SESAM is complicated and requires the use of molecular beam epitaxy(MBE)in an ultra-clean environment.Equipment,resulting in high production costs.In recent years,the discovery of saturable absorption properties of two-dimensional materials has attracted the attention of researchers,including transition metal chalcogenides(TMDs),topological insulators(TIs),black phosphorus(BP),and so on.Although some two-dimensional materials can be used in fiber lasers to generate pulsed lasers,they still have many shortcomings,such as the low modulation depth of graphene and the easy oxidation of black phosphorous.Among them,there are many types of TMDs,many of which have not been explored.It is expected that a new type of saturable absorber material can be found to solve the problems of SESAM.Therefore,the study of two-dimensional TMDs saturable absorber has important research significance.This paper has carried out the application research of several new two-dimensional TMDs such as tantalum disulfide(TaS₂),niobium sulfide(NbS₂)and tungsten sulfide(WS₂)in the signal modulation of fiber lasers.The specific research contents are as follows:(1)A mixed solution of absolute ethanol and deionized water was used as a dispersant for TaS₂ powder,and a dispersion of TaS₂ nanosheets was obtained by liquid phase ultrasonic stripping technology.The TaS₂ dispersion and the aqueous solution of polyvinyl alcohol(PVA)were mixed,sonicated and dried to form a TaS₂ saturable absorber film.For the first time,the TaS2 saturable absorber(TaS₂-SA)film was put into erbium and ytterbium doped Q-switched and mode-locked pulse output are obtained in fiber lasers.In the TaS₂-SA modulated Q-switched erbium-doped fiber laser,the repetition frequency is adjustable from 11.57 k Hz to19.87 k Hz,the corresponding pulse width varies from 17.67?s to 6.5?s,and the maximum pulse energy is 6 n J.TaS₂-SA was applied to a Ytterbium-doped fiber laser to obtain picosecond mode-locked pulse output.The pulse width was as narrow as 573.5 ps,and the center wavelength and repetition frequency were 1059.77 nm and 9.58 MHz,respectively.(2)The NbS₂ saturable absorber film was prepared using the same method as(1).In the Ytterbium-doped fiber laser modulated by the NbS₂-SA film,a nanosecond mode-locked pulse output is obtained,the pulse width is 2.8 ns,and the center wavelength and repetition frequency are 1060.8 nm and 9.157 MHz,respectively.At the same time,based on the NbS₂-SA,a stable Q-switched signal was obtained in a 1?m optical path.Under a pump power of130 m W,a Q-switched pulse sequence was obtained with a pulse period of 45.9?s and a pulse width of 6.5?s.(3)The laser output characteristics of WS₂-SA in passively mode-locked erbium-doped fiber lasers are studied.The WS₂ thin film is prepared on the silicon wafer substrate by magnetron sputtering combined with post-sulfurization treatment.Using dry transfer,the prepared WS₂ is transferred from the substrate through polystyrene(PS)to obtain a WS₂/PS composite The thin-film saturable absorber is then put into the erbium-doped fiber laser to modulate the mode-locked pulse.The pulse repetition frequency is 7.93 MHz,the corresponding period is 126.2 ns,the pulse width is 945 ps,and the signal-to-noise ratio is 51d B.The above experimental results show that TaS₂,NbS₂ and WS₂ have modulation effects in fiber lasers.In this article,the passive Q-switched erbium-doped fiber laser and passively mode-locked ytterbium-doped fiber laser based on TaS₂-SA are realized for the first time;the passive mode-locked based on NbS₂-SA and the passively Q-switched ytterbium-doped fiber laser are realized for the first time;The WS₂ prepared by the liquid phase lift-off method and CVD method,which is often reported before,is used for Q-switched and mode-locked fiber lasers.In WS₂-SA in passively mode-locked erbium-doped fiber lasers,the magnetron sputtering method is combined with post-sulfurization treatment in silicon.The WS₂ film was prepared on the substrate,and transferred from the substrate using polystyrene(PS)to obtain the saturable absorber of the WS₂/PS composite film for use in the Erbium-doped fiber laser.