A general solution of the heat diffusion equation is presented for the case of a semi‐infinite two‐layer system that is heated with a localized cw laser beam of Gaussian or uniform circular intensity profile. As an example, this theory is applied to thin layers of a thermoluminescent material on glass substrates. The transient thermoluminescence emission response is calculated and compared with experimental results, illustrating the validity of the solutions. Applications to transient laser heating of oxide‐semiconductor sandwiches are discussed.