In-fiber acousto-optic devices for laser applications

Several different in-fiber acousto-optic devices are generating new possibilities for the active control of Q-switched distributed feedback and mode-locked all-fiber lasers. Distributed feedback (DFB) lasers based on semiconductor technology have broader linewidths, typically in the MHz domain, due to low thermal dissipation and the use of short cavity lengths. Some in-fiber modulators are especially suited for modulating the Q-factor of a DFB fiber laser because, although fiber-pigtailed-packaged electro-optic or acousto-optic modulators have a higher switching speed, their use is not an available option. Both static and dynamic defects could be created within the fiber Bragg grating (FBG), either by using a DC or a modulated electrical current, respectively. Long-period grating (LPG) is usually fabricated by creating a periodic perturbation of the refractive index by UV radiation, which fixes its spectral characteristics.

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