The Application Of A New Saturable Absorber Based On LB Film Technology In Solid-state Lasers

The short pulse laser possesses many advantages,such as high repetition rate,high pulse peak power,high repetition frequency,and high single pulse energy.The process of short pulse interactions with matter has excellent characteristics,such as short action time,small action area,and so on.The short pulse laser has been widely used in different areas,such as minimally invasive surgery,material processing,signal detection fields et al.Short pulse laser technology has become one of the advanced production techniques of the innovation development of society.Saturable absorber(SA)plays a very important role in the operation of the short pulse laser techonogy.Therefore,the preparation of SA is crucial in short pulse laser fields.In recent years,some new style SAs with the characteristics of simple structure,easy manufacture,and low cost are reported,such as graphene,topological insulator,and transition-metal dichalcogenide.Those two-dimension nano materials impell passively mode locking and Q-switching to produce higher parameters of laser pulses.The manufacture technology of two-dimensional materials is mature,single layer of the two-dimensional materials could be obtained at present.The common two-dimensional(2D)material transfer methods include dip drop method,polymer composite coated method,and magnetron sputtering technique.However,there are some inherent flaws in those as-mentioned methods.The dip drop method is to directly drop SA solution onto the substrate,which leads to the non-uniform distribution of the SA sheets on the substrate.And the thickness of thin film is uncontrollable.Some unwanted impurities in polymer composite film cause additional scattering losses,moreover,reduce the damage threshold of absorbers,which will affect the application of the absorbers in high power laser system.Magnetron sputtering and ion bean aided evaporation,as the ways to improve the uniformity of large area coating need some expensive large equipments.In order to meet the low-cost requirements,we propose a Langmuir Blodgett(LB)method to fabricate the two-dimension materials film SAs.The main works in this paper as follow:(1)Under different surface pressure,the graphene oxide Langmuir Blodgett film saturable absorbers(GO LB SAs)is fabricated by LB technique.By comparing the thin film characterization of GO LB SAs prepared under different surface pressure,the selection GO LB SA with a transmittance of 89.0%is applied in all solid Nd:GdVO4 laser,and the passive Q-switched(QS)is realized.At the maximum pump power of 4.8 W,the average output power is 1.03 W,corresponding to a slope efficiency of QS laser is as high as 43.6%.(2)We propose to fabricate the molybdenum disulfide thin film SA(MoS2 LB SA)by a LB method,The characteristics of the films have been investigated by optical microscope,scanning electron microscopy(SEM),Raman spectrometer,atomic force microscope(AFM),and ultraviolet spectrophotometer(UV).Based on the MoS2 LB SA,a stable passively Q-switched(QS)Nd:GdVO4 laser(1064.0 nm center wavelength)is realized.At pump power of 6.0 W,the shortest pulse duration is 269.2 ns with a repetition rate of 1.03 MHz.The highest average output power,the slope efficiency of QS laser are as high as 1.392 W,35.9%,respectively.