Abstract
In ultrashort-pulse laser processing of semiconductors the residual stress is set jointly by photoexcited carriers, heat and absorbed moisture, relaxing on distinct time scales. Existing fractional photo-thermoelastic models confine memory to the heat-conduction law and leave the plasma and hygroscopic fields Markovian. We assign an independent fixed Caputo order to each transport channel: two to the thermal phase lags, one to moisture relaxation, and one to photocarrier transport, the last from a multiple-trapping retardation kernel carrying the mean trap release time, which recovers Fickian diffusion unconditionally. Variable thermal conductivity is handled by the Kirchhoff transformation; a transverse magnetic field enters as velocity-proportional damping commuting with the Helmholtz decomposition. The system is integrated with an L1 convolution quadrature per kernel, second-order finite differences and a block-implicit thermal–hygroscopic solve, and verified against manufactured solutions with closed-form fractional derivatives: all five fields converge at second order in space, with residuals of order 10−11. The memories act selectively: carrier and moisture memory alter the moisture field by roughly 30 % and 60 %, yet moisture memory reaches the carrier field some four hundred times more weakly than carrier memory, reflecting the one-directional coupling. Magnetic damping changes the interior normal stress by 16 %, about fifty times the carrier-memory effect, non-monotonically because Joule heating accumulates as the velocity decays. Intrinsic memory thus sets the material response; the applied field supplies the practical control.