Influence of the thermal effect on the output power in a flat-topped beam end-pumped DPL

The flat-topped beam is applied to describe the pump profile, formed by multi-fiber compact-arranged coupling and then being reshaped by lens. The pump profile of the flat-topped beam is given. Variation relations of the thermal induced diffraction losses caused by the thermal effect with variations of the pump power and the waist radius of pump beam have been numerically calculated. The influence of the thermal effect on the fundamental transverse mode output power has been discussed further. Experimental test on the variety regulation of the output power with pump power has also been done. The results show that the thermal induced diffraction losses reduce the output power obviously. With increasing of the waist radius of pump beam, the thermal induced diffraction losses and its effect becomes small; The higher the pump power, the bigger the thermal induced diffraction losses, and the stronger the influence on the output power of the fundamental transverse mode.