Optimal defect position in a DFB fiber laser

Abstract

Fiber lasers with compact cavity have numerous potential applications in sensing, communications, and medicine. Distributed feedback (DFB) rare-earth doped fiber lasers based on Bragg gratings with a phase shift are the most promising in this aspect. In this paper, we theoretically study such lasers and carry out a complex-frequency analysis of the DFB cavity modes. Our approach is based on the study of poles of open cavity response function and on the laser rate equations. An optimal defect position in the Bragg grating, which maximizes an output power towards one side, was found with this approach. We show that the optimal defect position depends on the pump power. At the pump level close to the lasing threshold, the defect should preferably appear in the middle of the grating to maximize the one-side output power. At higher pumping, the optimal position of the defect becomes asymmetric. We have found specific variables, which allow for determination of optimal defect position for a large variety of DFB laser configurations.

Extremely Efficient DFB Lasers with Flat-Top Intra-Cavity Power Distribution in Highly Erbium-Doped Fibers

“…The distributed feedback (DFB) fiber laser consists of a Bragg grating with a π-phase shift (PPS) written in an active fiber [ 1 ] and exhibits higher-order mode suppression as well as stable single-frequency operation [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Such π-phase-shifted gratings, initially used for DFBs in semiconductors [ 34 ], have also been implemented in erbium-doped fiber (EDF) DFB lasers [ 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]; however, the efficiency is still limited, whilst highly efficient unidirectional EDF-DFB lasers around 1.55 μm are of great importance for sensor technology, metrology, and spectroscopy amongst other applications [ 10 , 11 , 12 , 13 , 14 ].…”

“…First, DFB fiber lasers have been typically realized for constant-coupling fiber Bragg grating (FBG) with a small efficiency in which a significant part of the pump power is unused [ 8 , 9 ]. Second, by pumping a DFB, e.g., on the near side (NS), the dislocation of the PPS from the center of the grating to the far side (FS), results in enhanced unidirectionality, as a main part of the laser power leaves the FS; however, increased unidirectionality decreases efficiency [ 5 , 28 , 29 ]. Although, the grating’s coupling profiles resulting in maximum efficiency and unidirectionality in DFB fiber lasers have been reported in [ 8 , 9 , 30 , 31 , 32 ], optimizing such profiles in a highly EDF-DFB laser considering the role of background loss has not yet been addressed.…”

Operation regimes switching of erbium fibre lasers

“…Лазеры с узкой шириной линии и низким уровнем шума является одним из ключевых компонентов во многих областях применения современной волоконной оптики [8,38,39], таких как когерентная оптическая связь [40][41][42], высокочувствительные волоконные датчики и сенсоры [40,[43][44][45][46][47][48] и спектроскопия высокого разрешения [49]. Среди различных лазеров наиболее привлекательными источниками являются диодные лазеры [50][51][52], волоконные лазеры, включая волоконные лазеры с распределенной обратной связью [48,[53][54][55]. Учитывая, что порог генерации лазера является фазовым переходом [68,69] представим описание лазеров через критические индексы, для этого запишем:…”