Fiber laser assembly and method of generating light

摘要

A modal instability of a fiber amplifier may be reduced by coupling, e.g. splicing, a length of passive multimode optical fiber to an active multimode optical fiber of the fiber amplifier. Upon launching light into the passive optical fiber, some higher order transversal modes may be excited in the passive optical fiber. The higher-order modes may interfere with the fundamental mode in the passive multimode optical fiber. However, the intermodal interference of the launched modes does not cause thermal gradients in the passive optical fiber. Upon propagation in the passive multimode optical fiber, the excited optical modes may lose mutual coherence, causing a reduction of contrast of the intermodal interference pattern along the doped core of the active optical fiber, effectively reducing modal instability in the active optical fiber.

主权项

1. A fiber laser assembly comprising:
a light source for emitting signal light having a non-zero spectral width; a length of passive multimode optical fiber between first and second ends thereof, optically coupled at the first end thereof to the light source for receiving the signal light and propagating the signal light in a zero-order optical mode and a higher-order optical mode in the passive multimode optical fiber towards the second end thereof,
wherein upon such propagation, one of the zero-order or higher-order optical modes is delayed with respect to the other optical mode so as to at least partially reduce coherence therebetween at the second end of the passive multimode optical fiber due to the non-zero spectral width of the signal light, andwherein the length of passive multimode optical fiber is proportional to a coherence length of the signal light; and a length of active multimode optical fiber between first and second ends thereof, optically coupled at the first end thereof to the second end of the passive multimode optical fiber, for receiving and amplifying the zero-order optical mode as the zero-order optical mode propagates towards the second end of the active multimode optical fiber.