Temperature distributions for the bidirectional heat flow geometry consisting of transparent substrate/100 nm Al/polymer where laser irradiation occurs at the Al surface adjacent to the transparent substrate. For the case of this transparent substrate being (a) Al₂O₃ and (b) SiO₂, the steady-state (unmodulated) temperature profile is displayed as a contour in radius and depth, while the solid line is the magnitude of modulated temperature at r = 0 μm for a modulation frequency of 10 MHz. In both cases, positive depth depicts the Al/polymer side, while negative depth depicts the transparent substrate side. (c) depicts the steady-state surface temperature rise for the same bidirectional heat flow geometry where the transparent substrate is varied to span a wide range of thermal conductivities from Si (140 W m⁻¹ K⁻¹) to complete insulation. All thermal parameters used for these calculations are listed in Table 1.