Composite laser gain medium

A planar waveguide (PWG) comprising a core and two claddings;

• wherein said core and claddings being bonded together by a process including the steps of:
• (a) Machining the mating surfaces of said core and said claddings to be bonded to optical flatness;
• (b) Polishing the mating surfaces of said core and said claddings to be bonded to a surface smoothness of less than 1 nanometer root-mean-squared;
• (c) Bonding said core and said claddings concurrently by the wafer bonding process to form an initial bonded assembly wherein said core is sandwiched between said claddings;
• and
• (d) Heat treating the initial bonded assembly to strengthen the bond.

A planar waveguide (PWG) for amplification of laser light comprising a core and a cladding:

• (a) Said core being made of a laser optical host material selected from the group consisting of YAG, YLF, GGG, sapphire, Lu2O3, Y2O3, Dy2O3, and Sc2O3;
• (b) Said laser optical host material of the core doped with suitable laser ions selected from the group consisting of Yb3+, Nd3+, Er3+, Ho3+, Ti3+, and Tm3+;
• (c) Said cladding made of the same laser optical host materials as said core;
• (d) Said cladding being bonded to said core by a wafer bonding process to form an initial bonded assembly;
• and
• (e) Heat treating the initial bonded assembly to strengthen the bond.