Study On The Characteristics Of 1?m/1.5?m Dual-wavelength Pulsed Fiber Laser Based On Erbium-doped Fiber

Due to the unique advantages including compact structure and low cost,dual-wavelength pulsed fiber lasers have significant applications in many fields such as nonlinear frequency conversion,Raman scattering spectroscopy,pump-probe spectroscopy and supercontinuum generation,which becomes a research hotspot in the field of fiber lasers.The researches of dual-wavelength pulsed fiber lasers with different pulse width and pulse forms,not only have important academic significance,but also have practical significance.Based on the Er/ Yb co-doped fiber,the main contents of our research on 1 ?m/1.5 ?m dual-wavelength pulsed fiber lasers are shown as following:1.Firstly,methods for generating pulsed laser and pulse synchronization were introduced.Then,the development of pulsed fiber lasers including dual-wavelength pulsed fiber lasers had also been illustrated.2.A 1 ?m Q-switched and 1.5 ?m gain-switched dual-wavelength pulsed fiber laser had been demonstrated by using a single Er/Yb co-doped gain fiber for the first time to our knowledge.The wavelength-tunable ranges were 11.7 nm and 29.7 nm,respectively for both 1 ?m and 1.5 ?m pulses.It is suggested that the 1 ?m Q-switched pulses are generated via the saturable absorption effect of the unpumped Er/Yb co-doped fiber which acts as an effective fiber saturable absorber(FSA)aided by a 1.5 ?m oscillation cavity,whereas a reabsorption of 1 ?m Q-switched pulses from the Yb ions modulates the population inversion of Er ions periodically to generate 1.5 ?m gain-switched pulses at the same repetition rate as 1 ?m Q-switched pulses.3.For the first time to our knowledge,a 1 ?m/1.5 ?m dual-wavelength pulsed fiber laser mode-locked at the same repetition rate of 4.13 MHz had been demonstrated by using a single Er/Yb co-doped gain fiber.With the increase of pump power,the pulse duration enlarged from 1.23 ns to 5.56 ns for 1 ?m pulses,and from 0.91 ns to 3.04 ns for 1.5 ?m pulses.In addition,for the 1.5 ?m pulses,the wavelength-tunable range was 25.23 nm and the dual-wavelength phenomenon was also observed.It is suggested that the 1 ?m pulses operating in the dissipative soliton resonance(DSR)region are generated through the nonlinear polarization rotation(NPR)effect,whereas the 1.5 ?m oscillation cavity is synchronously pumped by a reabsorption of 1 ?m pulses from the Yb ions to generate 1.5 ?m mode-locked pulses.4.Based on the previous experiment,we obtained 1 ?m/1.5 ?m dual-wavelength picosecond laser pulses with the same repetition rate of 7.1843 MHz by changing the cavity length to adjust the dispersion and nonlinear effects in the cavity.At the maximum pump power,the pulse duration,single pulse energy and output power for 1 ?m pulses were 145.4 ps,1.41 nJ and 10.13 mW respectively,whereas they were 417.2 ps,0.38 nJ and 2.75 mW respectively for 1.5 ?m pulses.5.By using a double-clad Er/Yb co-doped gain fiber,we obtained high-energy 1 ?m and 1.5 ?m pulses operated in the DSR region based on the NPR mode-locked technique,whose repetition rates were 4.0196 MHz and 381.3 kHz respectively.It is suggested that the 1.5 ?m pulses are accompanied by strong perturbation(CW lasing and SRS),while the 1 ?m pulses are not.Maximum output power and single pulse energy for the 1.5 ?m pulses at the fundamental frequency were 572 mW and 1.5 ?J respectively.When increasing pump power furtherly,the 1.5 ?m pulses split into second order harmonic pulses.But the 1 ?m pulses kept wave-breaking-free even at the maximum pump power,whose maximum output power and single pulse energy were 356 mW and 88.6 nJ respectively.Moreover,both 1 ?m and 1.5 ?m pulses could be achieved simultaneously at suitable pump power.