| Microstructured optical fibers(MOFs)have the advantage of flexible structural design and excellent optical modulation capability.The targeted filling of functional materials and rational arrangement of the cladding structure can achieve efficient and stable optical modulation,and MOFs are widely used in sensing and communication fields.Meanwhile,subwavelength metallic gratings can also achieve effective modulation of the optical field at the subwavelength scale,and are used in reciprocal asymmetric electromagnetic transmission devices for the small footprint and passive operation,thus promoting the development of integrated optoelectronics technology.In this paper,the corresponding theoretical study and functional design of microstructured optical fibers and metallic gratings structures are carried out as follows:(1)A high-sensitive and transverse-stress compensated methane sensor based on a microstructured optical fiber long-period grating(MOF-LPG)is designed.Five of the six large side-holes of the MOF cladding were selected to be coated with methane sensitive films for methane detection.Since the large-holes facilitate the diffusion of methane molecules in the channel,but is not conducive to resist the interference of external stresses,it is necessary to add the surface plasmon resonance(SPR)sensing channel by plating silver nano-layer on the inner side of the remaining large-hole for compensation.Considering the photo-elastic effect and material deformation,the SPR channel can achieve the detection of transverse-stress,and the sensitivity of methane can reach 6.39 nm/% after transverse-stress compensation.The sensor has higher sensitivity,which provides a new method of gas measurement in complex environments.(2)A tunable multi-functional splitter based on dual-core photonic crystal fiber(DC-PCF)with temperature-controlled is designed.A mixture of chloroform and toluene is infiltrated in the two-cores of the DC-PCF to modulate the coupling characteristics of the DC-PCF by temperature.The splitter is capable of dividing two orthogonal polarization states for incident wavelengths from 1.30 ?m to 1.70 ?m over a temperature range of 10°C-27°C,where the maximum bandwidth and extinction ratio are 255 nm and-68 d B,respectively.Especially,the output polarization state of one core convert from y-polarization to x-polarization at certain high temperature points(>27°C).Meanwhile,the splitter realize the wavelength splitting of 1.30?m/1.49 ?m,1.30 ?m/1.55 ?m,0.85 ?m/1.55 ?m and 1.49 ?m/1.63 ?m by manipulating the operating temperature,and the splitter has better performance and easy to operate.(3)A dual-band asymmetric optical transmission(AOT)device with high contrast ratio based on bilateral compound metallic grating is designed,which consists of compound gratings with a silver strips on the outer surface,a thin Ag-film and inverted T-shaped gratings embedded in the substrate.When the forward wave vector modulated by grating diffraction matches the wave vector of Surface Plasmon polaritons(SPPs),the upper gratings unidirectionally excite the SPPs to generate a dual-band forward transmission.The device can achieve a high transmittance of 0.67 and 0.82 with a contrast ratio of 0.997 and 0.99 at operation wavelengths 627 nm and1238 nm,respectively.Moreover,the single-band AOT function is achieved by using SPPs coupling between two metallic structures to suppress the forward transmission in a specific frequency band.Finally,by adjusting the underlying parameters,the proposed structure having AOT characteristic at 624 nm and bi-directional transmission function at 1234 nm.The proposed structure is simple and feasible,and has great potential applications in the field of integrated optoelectronics. |
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