METHOD OF SELECTION OF TRANSVERSE MODES OF MULTIMODE FIBER LASER Russian patent published in 2018 - IPC H01S3/67 

FIELD: laser engineering.

SUBSTANCE: invention relates to laser equipment. Method of selecting transverse modes of a multimode fiber laser involves the use of Bragg gratings, at the same time, with equal resonance wavelengths of radiation reflection, corresponding to the selectable transverse mode of the multimode fiber; the formation of the end face of an output multimode optical fiber with an angle of more than 8°between the axis of the optical fiber and the normal to the end surface of the output optical fiber located after the output fiber Bragg grating. Output Bragg grating is additionally formed with a transverse-non-uniform profile of the refractive index in the core of the multimode fiber. Transverse-inhomogeneous profile is determined by the arrangement of single regions of refractive index modifications inside the core of the fiber and provides the maximum value of the coupling coefficient k_mp in the output grating for the selectable mode and the minimum value of the coupling coefficient k_m'p' for other transverse modes of a multimode fiber, which is determined according to formula

where Δn(r,φ) – the magnitude of the change in the refractive index at a point with coordinates (r,φ), E_mp(r,φ) – distribution of the transverse mode field of a multimode fiber with a radial index p and an azimuthal index m

where – the Laguerre polynomial, r₀ is the radius of the field of the fundamental transverse mode of a multimode fiber. Output grating is made in the core of the light guide at a distance of the resonator length from the input grating.

EFFECT: technical result is increased stability of the multimode fiber laser and simplified design.

11 cl, 5 dwg