【摘 要】
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We report the observation of second order Bragg resonance[2nd-OBG]produced by tilted fiber gratings[TFGs]fabricated using phase mask UV inscription.The theoretical analysis has revealed that the generation of high order Bragg resonance of gratings is indu
【机 构】
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School of Optical and Electronic Information,NGIA,Huazhong University of Science and Technology,Wuha
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We report the observation of second order Bragg resonance[2nd-OBG]produced by tilted fiber gratings[TFGs]fabricated using phase mask UV inscription.The theoretical analysis has revealed that the generation of high order Bragg resonance of gratings is induced by a square-shape refractive index profile,which is caused by over-saturated UV exposure.In the experiment,we have studied the TFGs with different tilt angles under over-saturated UV exposure,in which all gratings have showed the 2nd-OBR,and the larger tilt angle of the grating has the stronger 2nd-OBR.When the tilt angle of the grating is ～45°,the Bragg resonance exhibits very strong polarization dependence,because the 2nd-OBR wave-length is located within the polarizing bandwidth of 45° TFG.Finally,we have demonstrated an erbium-doped fiber laser with ＞ 99.9％ degree of polarization,and,by applying mechanical stretching on the grating,a wavelength tunable laser output has been achieved.The output laser shows ～0.2 dB amplitude variation within 1 h continuous monitoring of the laser.
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