Solid-state lasers pumped by incoherent or partially coherent, monochromatic light sources such as high power VCSEL arrays. Efficient and uniform injection of pumping energy into 
gain medium is achieved through spectral match of the pump source with the 
gain medium absorption and multi-bounce reflections of unabsorbed pump light in a diffusing 
pump chamber. One preferred embodiment of the diffusing 
pump chamber is a 
hollow cylinder coaxially surrounding the 
gain medium. One or more transparent windows, slit-shaped or otherwise, for transmission of pump light are evenly distributed around the perimeter of the chamber and are parallel to the axis. Another preferred embodiment of the diffusing 
pump chamber is a highly reflecting compound 
parabolic concentrator. A 2-D VCSEL array is employed as the pump source and the gain medium is located at the focusing point of the chamber. This invention demonstrates 
solid-state lasers that are compact, robust, low-cost, and able to produce 
high power output in CW or pulse 
modes for practical applications. An important application of the present invention is high-power 
solid-state lasers featuring 
wavelength conversion such as optical 
parametric oscillation and second-
harmonic generation. Another important application of the present invention is injection seeding, especially for 
pulse mode with high repetition rates.