Abstract: A single mode (SM) high power laser system is configured with a laser source outputting a single mode or low mode kW-power light and a passive delivery fiber spliced to an output fiber of the fiber laser source and having a double bottleneck-shaped core. The latter is configured to increase a threshold for nonlinear effects in general and in particular for stimulated Raman scattering (SRS) so that the delivery passive fiber has a fiber length at least twice the length of a delivery passive fiber with a standard uniformly dimensioned core, which may be used with the same laser source, while outputting the kW-power light with an M2 factor less than 2.

Abstract: The inventive laser is configured with a plurality of pigtailed multimode (MM) diode lasers each receiving a direct input current at a room temperature which is maintained to be within a 20-25° C. inside the housing of the laser. The diode lasers each are configured to operate at a desired wavelength in an optimal operational range, in which the diode laser operates with a WPE range between 63% and 75%. The direct current inputted in each diode laser is selected to be below a threshold at an efficiency curve of the diode laser after which the efficiency of the diode laser starts decreasing while an output power of the diode laser continues to increase. The laser is further configured with a fiber gain block having an active fiber medium which is pumped with the cumulative pump output and operative to emit a laser output in a power range between hundreds of watts and tens and even hundreds of kilowatts at the desired wavelength in an optimal operation range.

Abstract: The inventive laser is configured with a plurality of pigtailed multimode (MM) diode lasers each receiving a direct input current at a room temperature which is maintained to be within a 20-25° C. inside the housing of the laser. The diode lasers each are configured to operate at a desired wavelength in an optimal operational range, in which the diode laser operates with a WPE range between 63% and 75%. The direct current inputted in each diode laser is selected to be below a threshold at an efficiency curve of the diode laser after which the efficiency of the diode laser starts decreasing while an output power of the diode laser continues to increase. The laser is further configured with a fiber gain block having an active fiber medium which is pumped with the cumulative pump output and operative to emit a laser output in a power range between hundreds of watts and tens and even hundreds of kilowatts at the desired wavelength in an optimal operation range.

Abstract: A single mode (SM) high power laser system is configured with a laser source outputting a single mode or low mode kW-power light and a passive delivery fiber spliced to an output fiber of the fiber laser source and having a double bottleneck-shaped core. The latter is configured to increase a threshold for nonlinear effects in general and in particular for stimulated Raman scattering (SRS) so that the delivery passive fiber has a fiber length at least twice the length of a delivery passive fiber with a standard uniformly dimensioned core, which may be used with the same laser source, while outputting the kW-power light with an M2 factor less than 2.

Abstract: A high power fiber laser system includes a booster winch is configured as a fiber amplifier extending over free space, pump source and laser head including a reflective element which receives pump light and reflects toward the output end of the booster in a counter signal-propagating direction. The booster is configured with concentric and coextending frustoconically shaped (“MM”) core and cladding around the core. The core includes a mode transition region expanding between small diameter SM input and large diameter MM output core ends and configured so that amplification of high order modes is substantially suppressed as a single mode (“SM”) signal light propagates from the input to output core ends. The laser head receives output ends of respective pump light delivery fibers and signal fiber, respectively. The pump source is structured with a plurality of independent sub pumps arranged around the booster.

Abstract: A clad absorber unit is provided on a passive fiber of a high power fiber laser system and operative to trap and remove high order modes propagating along the clad of the passive fiber. The mode absorber has a composition made from one or more liquid metals and alloys thereof which are placed in the opening formed in the sheath of the passive fiber. The composition is configured to remove from the cladding the MM light having a predetermined light power which heats the composition at a temperature lower than a threshold temperature at which the absorber may be damaged.

Abstract: A clad absorber unit is provided on a passive fiber of a high power fiber laser system and operative to trap and remove high order modes propagating along the clad of the passive fiber. The mode absorber has a composition made from one or more liquid metals and alloys thereof which are placed in the opening formed in the sheath of the passive fiber. The composition is configured to remove from the cladding the MM light having a predetermined light power which heats the composition at a temperature lower than a threshold temperature at which the absorber may be damaged.

Abstract: A clad absorber unit is provided on a passive fiber of a high power fiber laser system and operative to trap and remove modes propagating along the waveguide clad of the fiber. The mode absorber is configured with such an optimal length that the clad light may be removed in a localized manner, substantially uniformly removed over the entire length thereof. The absorber removing clad light in a unformed fashion includes a host material impregnated with diffusers.

Abstract: A clad absorber unit is provided on a passive fiber of a high power fiber laser system and operative to trap and remove modes propagating along the waveguide clad of the fiber. The mode absorber is configured with such an optimal length that the clad light may be removed in a localized manner, substantially uniformly removed over the entire length thereof. The absorber removing clad light in a unformed fashion includes a host material impregnated with diffusers.

Abstract: A high power fiber laser system includes a booster winch is configured as a fiber amplifier extending over free space, pump source and laser head including a reflective element which receives pump light and reflects toward the output end of the booster in a counter signal-propagating direction. The booster is configured with concentric and coextending frustoconically shaped (“MM”) core and cladding around the core. The core includes a mode transition region expanding between small diameter SM input and large diameter MM output core ends and configured so that amplification of high order modes is substantially suppressed as a single mode (“SM”) signal light propagates from the input to output core ends. The laser head receives output ends of respective pump light delivery fibers and signal fiber, respectively. The pump source is structured with a plurality of independent sub pumps arranged around the booster.