| As one of the greatest inventions of the 20th century,laser have attracted people’s attention because of its advantages of good coherence,good monochromaticity,good directionality and high brightness.With the development of laser technology,high-energy nanosecond lasers play an increasingly important role in industries,scientific research,medicine,military and other fields.The birth of laser is a new milestone in the history of optics.All-solid-state ultrafast pulse lasers have many important applications in various fields due to their advantages of simple structure,stability,reliability,high slope efficiency,good beam quality,high single pulse energy,narrow pulse width,and high peak power.Q-switched lasers could be obtained one hundred times or one thousand times single-pulse energy than mode-locked lasers because of the lower repetition frequency(several to several hundred kHz)at the same power.In addition,the Q-switched laserscan also output short pulses in the order of ps at this stage,which is enough to meet the pulse width requirements in laser processing,medical and military fields.At the same time,the Q-switched laser also has the advantages of low cost,simple and compact structure,easy to calibrate the optical path,etc.,avoiding the defects of poor stability in the practical process of mode-locked lasers.Passively Q-switched lasers mainly uses the non-linear absorption of the saturable absorber to cause a sudden change in the energy of the resonator,thereby generating pulses.Compared with actively Q-switching lasers that requires a high-voltage RF driver,passively Q-switched lasers has a low cost,simple operation,and a simple structure that makes it easier to miniaturize the device.In the past two decades,people have achieved ultrashort pulse output of lasers with widely used of semiconductor saturable absorption mirror SESAM or metal ion-doped crystals as modulation elements to.However,due to the inherent complexity of the process and high cost of SESAM or metal ion doped crystals,scientists are actively exploring new saturable absorbers that can replace SESAM or metal ion doped crystals.With the continuous research of carbon nanotubes,graphene,topological bodies,transition metal sulfides,black phosphorus,as a new generation of saturable absorbers,compared with SESAM or metal ion doped crystals,the new absorbers are not only simple to prepare and low in cost,but also have a wider modulation band due to their own band gap characteristics;in addition,like graphene,transition metal sulfides And absorbers such as black phosphorus also have stronger nonlinear absorption characteristics,making them have great potential in high energy narrow pulse width lasers.However,the preparation method of the new absorber is not mature enough.Most absorbers attach materials to the surface of the cavity mirror or the quartz substrate by deposition or spin coating.These two-dimensional materials cannot form a large-area film structure uniformly,and there are obstacles to their own heat dissipation.In addition,there are no related heat dissipation measures.When the high-energy laser is irradiated on the surface of the absorber,it will be definitely damaged to a certain extent,poor affecting output laser.We adopt a simple,effective,and low-cost vertical growth method to prepare monomolecular films.This vertical growth technique has been used to prepare highly ordered monomolecular films.On this basis,the thickness of the film can be easily controlled at the nanometer level.Compared with the deposition or spin coating method,the nanomaterials prepared by the LB method are evenly distributed on the film.In addition,unlike the magnetron sputtering technology and the CVD technology,the film environment of the LB technology only requires normal temperature and pressure conditions to avoid the destruction of the nanomaterials and the film structure.Therefore,this technology can be applied to the study of the physical properties of nanomaterials.In this paper,a simple preparing method of a two-dimensional material saturable absorber film is used in the solid-state lasers at the bands of 1.06μm and 1.34μm respectively,and the passively Q-switched phenomenon is successfully generated.The two-dimensional material saturable absorber device is exploratory in the laser at the band of 1.34μm.The preparation of a two-dimensional material solution as a saturable absorber produces a passively Q-switched phenomenon,which is compared with the experimental results produced by a thin-film material in a solid-state laser.The research content of this article includes the following aspects:1.To introduce a passive Q-switched solid-state laser based on a saturable absorber,clarify the experimental content and development prospects,clarify the principle of passive Q-switching technology,and introduce two typical representative two-dimensional material saturable absorber material structures And its unique photoelectric characteristics.2.Introduce the preparation method of two-dimensional material saturable absorber.Investigate the types and manufacturing methods of saturable absorbers used in solid-state lasers,understand the preparation mechanism and corresponding advantages and disadvantages of different methods,focus on the research of liquid-phase stripping method for the preparation of two-dimensional material nanosheets,and the LB vertical pull-type film-making method.Two-dimensional material film is used to transfer the optical substrate.3.Reflective two-dimensional material saturable absorber devices based on GO and WS2 were prepared by LB method,and the prepared saturable absorber devices were characterized at the same time.The use of lower cost and simpler methods to prepare higher-quality thin film materials highlights the advantages of the LB method for the preparation of two-dimensional material saturable absorber thin films.4.The passively Q-switched solid-state lasers based on the two-dimensional material saturable absorber is studied.The prepared reflective GO saturable absorber was applied to a solid-state laser at the band of 1.06μm,and the advantages of the reflective saturable absorber in a solid-state lasers were verified,and the current similar saturated absorber in the passive Q-switched solid-state lasers was obtained.The maximum output power generated in the experiment.At the same time,in order to verify the wide band absorption of the reflective saturable absorber prepared by the LB method,a reflective saturable absorber device based on WS2 was prepared and successfully applied in a 1.34 μm passively Q-switched solid-state lasers for the first time.Considering the application of the solution saturable absorber device of two-dimensional material at the band of 1.06μm,the experiment attempts to prepare a WS2 aqueous solution and apply it in a 1.34μm solid-state laser to generate a passive Q-switching effect to obtain a pulse laser with a minimum pulse width of 55ns.It is confirmed that the two-dimensional material solution can be used as a saturable absorber in the 1.34 μm solid-state laser.5.Summary and prospect of the work of this thesis. |
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