A single frequency fiber Bragg grating (FBG) stabilized laser at 972 nm is coupled into a doubling ring cavity with an
optical length of 138 mm, a 91% input coupler, a 30 mm long Brewster cut magnesium doped periodically poled lithium
tantalate (PPMgO:SLT) crystal and a high reflector. The cavity buildup is 37 and loss is 0.63%. The cavity is monitored,
controlled and locked with a single chip processor. With IR power of 572 mW in the input fiber, 466 mW blue output is
obtained, giving 81.5% net efficiency. The blue and IR beams are separated by refraction at the crystal’s Brewster surface
with negligible loss and without the need for dichroic optics.