Distributed feedback lasers
AssigneeBritish Telecommunications public limited company
InventorLeslie D. Westbrook
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Abstract
Improved single-modedness is achieved in distributed feedback (DFB) lasers by minimizing the feedback provided at or near the ends of the DFB grating. The feedback may be minimized at one or both ends of the grating. Feedback is controlled by reducing the coupling to the grating. Coupling is reduced by reducing the depth of the grating's teeth and/or by increasing the spacing of adjacent teeth.
Claims15
A distributed feedback laser comprising a laser medium and optical feedback to said laser medium, the optical feedback comprising periodic perturbations of the refractive index and/or gain of the laser medium, wherein said periodic perturbations are provided in a grating region which is distributed along the laser, the level of feedback provided by said perturbations varying throughout said grating region, characterised in that said level of feedback tends to zero at at least one of the ends of said grating region.
A distributed feedback laser comprising a laser medium and optical feedback to said laser medium, wherein a grating provides said optical feedback, the optical coupling of said grating varying with position along its length, characterised in that throughout the length of said grating there are no abrupt changes in the degree of coupling, and in that adjacent at least one of the ends of said grating the coupling tends smoothly to zero.
Dependencies are inferred from the claim text.