Erbium-doped Fiber Laser Based On Saturable Absorber

With the development of low-dimensional materials that exhibit excellent optical properties,such as include high nonlinearity,ultra-fast response time and ultra-wide operating range,can be used to make saturable absorption(SA)devices.These materials include carbon nanotubes(CNT),graphene,topological insulators,transition metal disulfides(TMD),black phosphorus,etc.Passively Q-switched and mode-locked based on saturable absorber are the main technology to obtain ultrashort pulsed laser SA.Therefore,seeking SA with simple preparation process,low cost and stable optical performance to meet the application requirements of various ultrafast pulsed laser attract wide attention of researchers.In this paper,CNT and WS2 are used as SA to build erbium-doped fiber lasers to obtain three types of pulsed laser output.The specific content includes;1.Using polyvinyl alcohol material(PVA)to prepare WS2-PVA film SA,we successfully build a dual-wavelength Q-switched fiber at 1528.61 nm and 1531.15 nm,which based on WS2-PVA SA with a total cavity length of 10.6 m.The pulse duration and intensity of the dual-wavelength Q-switched are the same.At a pump power of 185mW,the pulse duration,maximum single pulse energy and repetition rate of fiber laser are record as 1.14 ?s,29.5 nJ and 115.9 kHz,respectively.2.Based on Single-walled CNT have the characteristics of simple preparation process,low cost and large absorption range.We prepare CNT-PVA film as SA to build Q-switched fiber laser with a total cavity length of 16.8 m.At the maximum pump power of 222 mW,the central wavelength,pulse duration,maximum average output power,single pulse energy and repetition rate are recorded as 1557 nm,3.897 mW,1.8?s,66.2 nJ and 58.28 kHz,respectively.3.To increase the output power of the laser,we prepare CNT-SiO2 SA by the sol-gel method,that has the advantages of higher damage threshold and stronger fiber compatibility than SA prepared by PVA,and successfully build an ultrafast mode-locked fiber laser in which the erbium-doped fiber is 0.4 m and the total cavity length is 13.2 m.At a pump power of 517 mW,we obtain a traditional soliton mode-locked pulsed laser output,with central wavelength of 1558 nm,average output power of 13.76 mW,repetition rate of 15.9 MHz,a pulse duration of 850fs,and a signal-to-noise ratio of 45 dB.