ASYMMETRIC PWG WITH ASYMMETRIC COOLING

A planar waveguide (PWG) having a first end for coupling to a light pump and a second end opposite to the first end and including: a first cladding layer; a uniformly doped core layer having the first cladding layer on one side, wherein the core layer is tapered having a smaller thickness at the first end and a larger thickness at the second end; and a second cladding layer thinner than the first cladding layer, coated on another side of the core layer opposite to said one side of the core layer. The first cladding layer may also be tapered along the length of the PWG having a larger thickness at the first end and a smaller thickness at the second end with a taper angle substantially opposite that of the core layer to form the PWG with a substantially uniform overall thickness along the length.