I have the following plots
a1 = Plot3D[Sin[x y], {x, 0, 2 π}, {y, 0, 2 π},
PlotRange -> All];
a2 = Plot3D[Sin[x y]^2, {x, 0, 2 π}, {y, 0, 2 π},
PlotRange -> All];
a3 = Plot3D[Sin[x y]^3, {x, 0, 2 π}, {y, 0, 2 π},
PlotRange -> All];
a4 = Plot3D[Sin[x y]^4, {x, 0, 2 π}, {y, 0, 2 π},
PlotRange -> All];
a5 = Plot3D[Sin[x y]^5, {x, 0, 2 π}, {y, 0, 2 π},
PlotRange -> All];
a6 = Plot3D[Sin[x y]^6, {x, 0, 2 π}, {y, 0, 2 π},
PlotRange -> All];
Grid[{{a1, a2, a3}, {a4, a5, a6}}]
Is it possible to use a common label for the z-axis as $\sin^n(xy)$, and also use the individual plot labels as $n=1$, $n=2,\dots,n=6$.