Graphene-induced unique polarization tuning properties of excessively tilted fiber grating

Abstract

By exploiting the polarization-sensitive coupling effect of graphene with the optical mode, we investigate the polarization modulation properties of a hybrid waveguide of graphene-integrated excessively tilted fiber grating (Ex-TFG). The theoretical analysis and experimental results demonstrate that the real and imaginary parts of complex refractive index of few-layer graphene exhibit different effects on transverse electric (TE) and transverse magnetic (TM) cladding modes of the Ex-TFG, enabling stronger absorption in TE mode and more wavelength shift in TM mode. Furthermore, the surrounding refractive index can modulate the complex optical constant of graphene and then the polarization properties of the hybrid waveguide, such as resonant wavelength and peak intensity. Therefore, the unique polarization tuning property induced by the integration of graphene layer with Ex-TFG may endow potential applications in all-in fiber modulator, fiber laser and biochemical sensor.

Few-Layer Graphene Integrated Tilted Fiber Grating For All-Optical Switching

“…Then the copper foil was chemically etched, leaving a five-layer and ~15 mm long graphene film floating on top of the water. Further, the few-layer graphene film was wrapped around the TFBG by a wetting transfer technique [25]. Figure 1(b) displays the optical microscopic image of the graphene-integrated TFBG under bright-field, showing the uniform graphene coating.…”

Graphene oxide-deposited tilted fiber grating for ultrafast humidity sensing and human breath monitoring

“…The grating period along the fiber axis is much larger than that of the initial period determined by the phase mask, and thus the forwardpropagating core mode will be coupled into forward-propagating cladding modes [33]. The largely tilted fringes will locally break the cylindrical symmetry of the fiber core and induce a strong birefringent effect, and then the TFG demonstrates a noticeable multi-notch dual-peak feature [32], including two orthogonal resonance peaks of transverse electric and transverse magnetic cladding modes. Determined by the phase matching condition, the resonant wavelength of the mth cladding mode can be expressed as follows:…”

“…The sensor is also applied in real-time monitoring the human breathing with different frequencies, showing an ultrafast and reversible response of ~42 ms response time. Different from geometry-modified fibers which require complicated processes of etching, polishing, or tapering, the TFGs retaining a robust mechanical structure have been used for light-matter interaction and bio/chemical sensing [29][30][31][32]. The reliabilities of easy fabrication and GO integration, combining with the high sensing performances, promise many potential applications in pharmaceutical processing, human health and environmental monitoring.…”

Plasmonic Optical Fiber-Grating Immunosensing: A Review

“…Excessively tilted fiber gratings (ETFGs) are characterized by a tilt angle θ > 45° [ 44 , 45 , 46 , 47 ]. Given the very high angle value, they couple light to the cladding in the forward direction and present a hybrid behavior between the aforementioned weakly tilted FBGs and the long-period fiber gratings introduced in Section 2.5 .…”