In this paper, a novel all-fiber Q-switched single mode Er/Yb co-doped double clad fiber ring laser operating in 1548.11nm is reported, which exploits fiber Bragg grating Sagnac loop mirror as a wavelength-selective device. To obtain higher output power, the laser is pumped by six CW laser diodes operating at 976nm through six pigtails of a Tapered Fiber Bundle connected with the EYDF. When the pump power is 718.9mW, stable self Q-switched pulse series with pulse width of 2.8μs, repetition rate of 50kHz and peak power of 274.3mW are achieved. Self mode-locked pulse is also obtained in such experimental setup.
Large mode area (LMA) Yb-doped double clad fiber lasers with high power are theoretically and experimentally investigated. For a Fabry-Perot cavity structure, we show the dependence of output power on the output mirror reflectivity, coupled pump power and fiber length, respectively by using power propagation equations and rate equations. Stable CW operation of the fiber laser at 1064 nm with maximum power 4.6 W and slope efficiency 82.6% is achieved in the experiment.
An efficient and tunable Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped cladding pumped fiber ring laser operating in L-band is demonstrated.
Rejecting the amplified spontaneous emission (ASE) of C-band by a fiber Bragg grating (FBG) into the same Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped fiber, the laser can operate in L-band stably. The insertion of the FBG can reduce the lasing threshold, and narrow the 3dB line-width of output laser. Using a two-section high-birefringence fiber loop mirror as a wavelength filter, the output wavelength can be tuned over 40nm range. The lasing threshold is about 48.80mW and the side mode suppression ratio is better than 51dB.
A tunable Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped cladding-pumped all fiber ring laser is presented. Under the maximum pump power of 3594.5mW, the absorbed pump power of the fiber is measured to be 2737.37mW, the maximum output power of the fiber laser is 438mW, and the slope efficiency is greater than 15.9%. By using a fiber Bragg grating (FBG) as a wavelength filter, the linewidth of output laser is as narrow as 0.04nm by 3 dB, and by compressing or stretching the FBG, tuning range of 4.0nm is realized, the side mode suppression ratio is about 42dB. We also study the relationship between the output power and the splitting ratio of the output coupler, and it is found that there is an optimum splitting ratio of the output coupler at which the highest output power can achieve 647mW.
A high efficiency Q-switched and self-mode-locked Er<sup>3+</sup>/Yb<sup>3+</sup> co-doped fiber ring laser with a Mach-Zehnder interferometer (MZI) is proposed. The fiber laser with threshold of 126.84 mw and linewidth of 0.06nm has been demonstrated. The average power of 62.6mW, the peak power of 1231.8mW of the Q-switched giant pulses with the pulse duration of 2.6μs can be achieved. It is found that in order to generate Q-switched giant pulses, different repetition frequency must be selected as pumping power is changed. This phenomenon is observed for the first time to our knowledge. In the experiment, it is also found that stable passive Q-switch pulses can be observed, which waveform is not the same with the different pump power, although the arms lengths of the interferometer is not changed. When the absorbed pumped power is increased to 591.8mW, a self-mode-locking pulse can be formed and it is given a detailed theoretically illustration in this paper.