A semiconductor device includes a III-nitride substrate, a first III-nitride epitaxial layer coupled to the III-nitride substrate and having a mesa, and a second III-nitride epitaxial layer coupled to a top surface of the mesa. The stator and rotor being confrontationally disposed and spaced apart by a non-uniformly dimensioned axial gap. In one recording mode therefor, the disc is rotated at a constant angular velocity so as to have a linear velocity of 3-4 ms on an innermost track and a linear velocity of 8-9 ms on an outermost track. A transition is provided from the single ridged waveguide to rectangular waveguide in the side ports. These two packs are combined to form the novel adhesive composition.