Binfeng Yun

Highly Sensitive Liquid-Level Sensor Based on Etched Fiber Bragg Grating

A highly sensitive liquid-level sensor based on etched fiber Bragg grating (FBG) is proposed and demonstrated. The transmission dips of FBG spectra are affected by the fraction of the length of the etched FBG that is surrounded by the liquid. The experiments show that for a liquid-level variation of 24 mm, the transmission dip difference changes about 32 dB. Also in the linear region, a high sensitivity of 2.56 dB/mm is achieved.

Theoretical analysis of a nanoscale plasmonic filter based on a rectangular metal-insulator-metal waveguide

A compact and nanometric surface plasmon polariton (SPP) band-pass filter based on a rectangular ring resonator composed of metal–insulator–metal waveguides is proposed. Using the finite difference time domain method, the effects of the structure parameters on the transmission characteristics of this SPP band-pass filter are analysed in detail. The results show that the proposed SPP filter has narrow transmission peaks and the corresponding resonance wavelengths can be linearly tuned by altering the resonators cavity length. Moreover, the transmission ratios of the pass bands can be tuned by changing the coupling gaps between the input/output MIM waveguides and the resonator. Also the metal loss and dispersion effects on the filter responses are included. The simple band-pass SPP filter is very promising for high-density SPP waveguide integrations.

Cladding mode resonances of etch-eroded fiber Bragg grating for ambient refractive index sensing

In this Letter, the cladding mode resonances of a chemical etch-eroded fiber Bragg grating are proposed for highly sensitive ambient refractive index sensing. The varying characteristics of several different order cladding mode resonances with ambient refractive index are explored experimentally. The maximum sensing sensitivity of 172nm∕riu for the third-order cladding mode resonance is achieved in the experiments. Under the same cladding diameter, the cladding mode resonances have narrower bandwidth and response much more sensitive to the ambient refractive index changing than conventional Bragg core mode resonance, which would enable them to achieve a higher resolution.

A fiber Bragg grating sensor system for simultaneously static and dynamic measurements with a wavelength-swept fiber laser

A novel fiber Bragg grating (FBG) sensor system for static and dynamic measurements with a wavelength-swept fiber laser is proposed and demonstrated. In this system, both static and dynamic perturbation of each FBG in the sensor arrays can be interrogated simultaneously. The experiments demonstrated the strain resolutions of /spl sim/1 /spl mu//spl epsiv/ and 3.4 n/spl epsiv///spl radic/Hz at 500 Hz for static and dynamic measurements, respectively.

Multiwavelength generation in a Raman fiber laser with sampled Bragg grating

Simultaneous continuous-wave multiwavelength operation of a Raman fiber laser is demonstrated with sampled Bragg grating (SBG) at room temperature. The characteristics of multiwavelength fiber ring laser can be easily controlled by adjusting the parameters of the SBG, including the sampling period and the sampling length. In the proposed fiber laser, stable four oscillating wavelengths with 100- and 50-GHz spacing has been achieved, respectively, as well as five oscillating ones with a wavelength spacing of only 25 GHz by varying the sampling period of the SBG.

Theoretical and experimental study on etched fiber Bragg grating cladding mode resonances for ambient refractive index sensing

The theoretical model of etched fiber Bragg grating (FBG) backward cladding-mode resonances for ambient refractive index sensing is presented. The dependent behaviors of the mode resonances have been analyzed in the etching process and the ambient refractive index changed. The analysis is based on the classical coupling-mode theory while considering interactions among multiple modes and developed on a three-layer step-index fiber geometry. Experimental data match the theoretical model wonderfully. This model not only describes the relationship between the FBG backward cladding-mode resonances and the ambient index but also is valuable for the design of a flexible highly sensitive ambient index sensor.

Resonant Mode Analysis of the Nanoscale Surface Plasmon Polariton Waveguide Filter with Rectangle Cavity

The resonant mode characteristics of the nanoscale surface plasmon polaritons (SPP) waveguide filter with rectangle cavity are studied theoretically. By using the finite difference time domain method, both the band-stop- and band-pass-type rectangle SPP filters are analyzed. The results show that the whispering gallery mode (WGM) and the Fabry–Perot (FP) mode can be supported by the rectangle SPP resonator. Furthermore, both traveling-wave mode and standing-wave mode can be realized by the WGM, while only standing-wave mode can be introduced by the FP mode. The traveling-wave mode can only be realized by the square-shaped SPP resonator, and the traveling-wave mode is splitted into two standing-wave modes by transforming the cavity shape from square to rectangle. Also, the effects of the cavity shape, cavity size, and coupling gap size on the transmission spectra of the SPP resonators are analyzed in detail. This simple SPP waveguide filter is very promising for the high-density SPP waveguide integrations.

Characterization of a high birefringence fibre Bragg grating sensor subjected to non-homogeneous transverse strain fields

Several theoretical and experimental studies have been carried out in recent years to characterize the spectral response of an optical fibre Bragg grating (FBG) subjected to non-homogeneous axial strain fields. However, few works have considered the evolution of the spectrum when a FBG fabricated in a high birefringence fibre is subjected to non-homogeneous transverse loading. In this paper, a physical model is described and a numerical simulation based on the piecewise-uniform approach is also used to calculate the response of a FBG fabricated in a high birefringence fibre under some typical non-homogeneous transverse strain fields. Finally, simulated results are analysed and compared with a FBG fabricated in a conventional monomode fibre.

Broadband visible-light absorber via hybridization of propagating surface plasmon.

We demonstrate a broadband visible-light absorber based on excitation of multiple propagating surface plasmon (PSP) resonances. The simple structure is constructed of continuous gold/silica multi-layers covered by a one-dimensional gold grating. The broadening of bandwidth arises from the inter-layer hybridization and spectral superposition of PSPs, which is predicted with the analytical coupled oscillator model and validated using the RCWA simulation. The average absorption increases with the number of gold/silica pairs and exceeds 95% over the whole visible spectrum when only five pairs are included. Moreover, results show that the absorption can be further enhanced by grading the thickness of silica layers. The presented design might enable promising applications in the fields of photovoltaic cells and thermal emitters, owing to its advantages of wideband, near-unity absorption and simple fabrication simultaneously.

Plasmon induced transparency in metal–insulator–metal waveguide by a stub coupled with F-P resonator

A simple and compact metal?insulator?metal (MIM) stub coupled with Fabry?Perot (FP) resonator is proposed to realize the plasmonic analogue of electromagnetically induced transparency. By the coupling between the stub and the FP resonator, a narrow transmission peak is formed in the broad stop-band of the stub resonator. By combining the magnetic field distributions and the plasmon hybridization theory, the physical mechanism is presented, which is the mode splitting caused by the evanescent coupling between the plasmonic resonators. And the effects of the structure parameters on the transmission characteristics of the coupled system are analyzed in detail. Also, double plasmon induced transmission peaks can be realized by simply adding a second FP resonator into the system. The proposed compact and simple plasmonic structure may have potential applications in nanoscale filter and slow-light devices.