In-fiber comb-like linear polarizer with leaky mode resonances

Abstract

Leaky mode resonance (LeMR) has been proven as a promising high-performance and effective technology for fiber-optic devices. Here, we propose and theoretically demonstrate an in-fiber comb-like linear polarizer based on enhanced LeMR (eLeMR) in tilted fiber grating (TFG) with indium tin oxide (ITO) nanocoating. The ITO nanocoating induces the guidance of TE-polarized leaky modes, and hence greatly enhances the mode coupling with the core guided mode, which leads to the excitation of dense comb-like TE eLeMRs. By optimizing the ITO thickness and grating length, the results show that the eLeMRs can be designed to realize a novel in-fiber comb-like linear polarizer with remarkable polarization extinction ratio (PER) up to 57dBand ultra-narrow bandwidth (full width at half maximum, FWHM) smaller than 0.5nm, together with wavelength separation between adjacent bands equal to 3.1nm, in a broad wavelength range. Moreover, the operating wavelength of the polarizer can be further tuned by tailoring the grating parameters, like the period and tilt angle of the TFG. The designed polarizer will cover a wide range of applications including multi-wavelength fiber lasers, dense wavelength-division-multiplexed (DWDM) systems, optical spectrometers, and fiber-optic sensing systems.