One novel Topas-based Photonic Crystal Fiber (PCF) has been modeled and analyzed for chemical analytes detection in terahertz frequency range. The sensor was realized by filling different kinds of chemical analytes in the hollow core of the PCF, consisting of five layers air holes of hexagonal lattices in the cladding. The propagation characteristics of proposed sensor have been investigated by adopting the Full Vectorial-Finite Element Method (FV-FEM) with anisotropic perfectly matched layers (PMLs). Numerical results indicated that the hollow-core provided a high relative sensitivity as well as low transmission loss. When optimal design parameter was selected as core diameter 𝐷core = 400 μm, the PCF sensor showed high relative sensitivity of 80.32%, 83.3%, 84.64% with negligible confinement loss of 1.01×10−10 cm−1, 7.65×10−11 cm−1, 7.49×10−11 cm−1 at 1 THz frequency for Water, Ethanol, Benzene, respectively. Moreover, other important mode properties such as the core power fraction, Effective Material Loss and dispersion, were discussed completely in the terahertz frequency range. With the outstanding waveguiding properties, the simple sensor can be produced at a low cost and provided a new avenue for chemical sensing.
In this paper, a temperature sensor based on photonic crystal fiber (PCF) is designed and proposed. The temperature sensing is realized by filling different concentration ratios thermo-optic liquids of Ethanol-Toluene in the innermost layer six airholes of the PCF, which is consisting of a solid core and five layers air holes of hexagonal lattices. The propagation characteristics of proposed sensor have been investigated by adopting the full vectorial-finite element method (FV-FEM). The relationship between effective refractive index (neff), effective mode area (Aeff), confinement loss (Lc) and temperature have been numerically simulated. Simulation results show that both neff and Aeff are decreased with the increasing of temperature for a constant wavelength. The confinement loss peak occurs uniform red-shifted when the temperature rises, which indicate a linear relation between the wavelength of the loss peak and temperature of thermo-optic liquids. Furthermore, the working temperature range of the sensor can be adjusted by mixing different ratios of the thermo-optic liquids, the temperature sensitivity is as high as 6 nm/°C. The new sensor can also be produced at a low cost and provides a new avenue for ultrasensitive temperature sensing.
In this paper, the fabrication mechanism of Fiber Bragg Gratings (FGBs) in standard SMF-28 telecommunication fibers without hydrogen loading were explored by using point-by-point (PBP) direct writing method based on femtosecond laser with pulse duration of 100fs, 1kHz repetition rate, a central wavelength of 800nm. And more, a series of FBGs were successfully fabricated. The spectral characteristics of FBGs were explored by adjusting grating period, grating length and laser power. And the FBGs with different center wavelengths and periods were fabricated in order to obtain optimal spectral properties. The result shows that the resonant peak intensity is strengthen when the grating length and laser power was improved. This research will demonstrate the potential application of the developed FBGs for use in multi-wavelength fiber lasers and a variety of high temperature applications.
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