A Novel 3-D Microcavity Based on Bragg Fiber Dual-Tapers

In this paper, a novel 3-D microcavity based on Bragg fiber dual-tapers is proposed. The principle and characteristics of the Bragg fiber dual-taper are analyzed firstly, showing that the dual-taper can function as a fiber mirror. Its reflection and transmission can be adjusted by the design of taper structure parameters. Then, the structure of a 3-D microcavity composed by two Bragg fiber dual-tapers is investigated by the finite-difference time domain method. The relation between the cavity-mode wavelengths and the cavity lengths shows that it can be looked as a Fabry-PEacuterot cavity, using the Bragg fiber dual-tapers as the mirrors. By proper design, a cavity-mode Q factor up to 4.0093times10⁶ can be realized in this cavity. Its characteristics as narrowband filters are investigated, showing that its transmission spectrum has the shape of Lorenz curve and a finesse up to 10⁵ can be realized if cavity mode with a high Q factor is used. The analysis shows that high-quality 3-D light confinement can be realized in the proposed Bragg fiber dual-taper microcavity, which has great potential in high-efficiency light-emitting devices and small fiber components.