Fiber laser switched by a long period grating interferometer as an intra-cavity loss modulator

Q-switched Tm-doped fiber lasers using dynamic microbends in oval-coating fibers

“…As shown by the photograph in figure 1, the upper and lower corrugated plates had four and five teeth, respectively, so that they made four periods of microbend in the fiber. A fiber microbend with so few periods induces a quasi-long-period grating, which exhibits a broad rejection bandwidth [8]. The spatial period and the duty-ratio of the corrugated plates were formed as 750 µm and 0.5, respectively, so that the propagating core mode was efficiently coupled to the radiation cladding mode around λ = 1.9 µm.…”

“…However, most of them are made of bulk or waveguide devices that require precise optical alignment between the switching devices and the fibers, even if such devices are connected to fiber pigtails. An in-fiber Q-switching technique is desirable due to compactness, low-loss resonator, and robustness, and thus far has been demonstrated by using an evanescent coupler, a fiber Bragg grating, a long-period grating, and a microbend [6][7][8][9]. Considering the effective use of the broad emission band of the TSF laser, the switching element should not be sensitive to oscillation wavelength.…”