High power high efficiency fiber laser and method for optimizing wall plug efficiency thereof

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. The optimal operational ranges of respective MM diode lasers and fiber gain block are matched to achieve a superposition of respective efficiency maximums providing an overall maximum system efficiency up to 55%.