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In this paper, a three-section periodical grating structure (PGS) is investigated for Smith-Purcell (SP) backward wave oscillator (BWO). The first and second sections are used to pre-modulate the electron beam and the open grating (section-III) is for terahertz SP radiation. By theoretical analysis and particle-in-cell simulations, the SP radiation is studied in detail. The results show that the three-section...
This paper presents a simulation of Smith-Purcell (SP) radiation from dielectric loaded grating (DLG) at terahertz frequencies, which is performed by using a two-dimensional (2D) particle-in-cell (PIC) code. The simulation supposes a continuous electron beam passing over a DLG and metal grating, respectively. The results show that compared with metal grating, the usage of DLG can enhance the radiation...
In this paper, a simulation on the evanescent wave of Smith-Purcell (SP) radiation from dielectric loaded grating (DLG) is presented at terahertz frequencies. The evanescent wave provides feedback to bunch the electron beam, which is the basis of oscillator operation of SP free-electron laser (FEL). The results obtained from particle-in-cell (PIC) code are compared with metal grating, which show that...
Silicon photonics has been a very buoyant research field in the last several years mainly because of its potential for telecom and datacom applications. However, prospects of using silicon photonics for sensing in the mid-IR have also attracted interest lately. In this paper, we present our recent results on waveguide-based devices for near- and mid-infrared applications. The silicon-on-insulator...
In this paper, a dielectric loaded grating is proposed to enhance the Smith-Purcell (SP) radiation at terahertz frequencies. By using two-dimensional particleincell (PIC) code, the radiation power of dielectric loaded grating with different currents is simulated. The results show that compared with the metal grating, the dielectric loaded grating can decrease the threshold current and improve the...
A novel type of slow-wave structure for Smith-Purcell device called dielectric loaded metal grating, is proposed in this article. The three-dimensional (3D) analytical theory for the “hot” dispersion relation is derived using the field matched method and the results accord well with the simulation data performed by using 3D particle-in-cell (PIC) code.
In this paper, with the help of a two-dimensional (2D) particle-in-cell (PIC) code, a simulation of Smith-Purcell (SP) radiation from the dielectric loaded grating is performed in the terahertz regime. The results show that the SP radiation frequency is in good agreement with the theoretical curve. Comparing with the general grating, the usage of dielectric loaded grating enhances the evanescent wave,...
Spectral characteristics of multiple and cascaded phase-shifted fiber Bragg grating (FBG) are analyzed based on the coupled-mode theory with the transfer matrix method. It shows that multi-wavelength output (or comb filters) can be obtained by increasing the number of the phase shifts. The peak wavelength of the transmission band of the cascaded phase-shifted FBG will move towards long wavelength...
A refractive index sensor based on adjusting gap fiber Bragg grating was designed. Spectral characteristics of gap FBG are analyzed based on the coupled-mode theory with the transfer matrix method. As the refractive index of the media in the gap increased, the peak wavelength has a red-shift. Through measuring the reflectivity of the side band, the refractive index of media in the gap can be obtained.
Reflective spectral of multiple and cascaded phase-shifted fiber Bragg grating are analyzed based on the coupled-mode theory with the transfer matrix method. For n cascaded phase-shifted FBGs, there are n-1 transmission wavelength output.
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