Laser-Induced Thermal Effect for Tunable Filter Employing Ferrofluid and Fiber Taper Coupler

In this letter, an all-optically tunable filter based on laser-induced thermal effect has been proposed by employing a fiber taper coupler immersed in the magnetic fluids. Tunable spectral characteristics of the optically controlled fiber filter have been theoretically analyzed and experimentally investigated. Experimental results indicate that as the pump power varies from 0 to 216.1 mW, and the proposed filter shows a large wavelength shift of 58.2 nm. Moreover, it exhibits a nonlinear spectral shift behavior in response to the applied pump light intensity with good spectral repeatability. With such desirable advantages as compactness, ease of fabrication, and high spectral tunability, our proposed all-optically tunable filter would be a promising candidate for fiber laser and amplification, fiber-optic sensing, and optical fiber communications applications.