  In a recent work, assuming a Beer-Lambert optical absorption and a Gaussian
laser time profile, the exact solutions for a 1D-photoacoustic(PA)-boundary
value problem predict a null pressure for optically strong absorbent materials.
To overcome this, a heuristic correction was introduced by assuming that heat
flux travels a characteristic length during the duration of the laser
pulse\cite{Ruiz-Veloz2021} $\tau_p$. In this work, we obtained exact solutions
in the frequency domain for a 1D-boundary-value-problem for the Dual-Phase-Lag
(DPL) heat equation coupled with a 1D PA-boundary-value-problem via the
wave-equation. Temperature and pressure solutions were studied by assuming that
the sample and its surroundings have a similar characteristic thermal lag
response time $\tau_{_T}$, which was assumed to be a free parameter that can be
adjusted to reproduce experimental results. Solutions for temperature and
pressure were obtained for a three-layer 1D system. It was found that for
$\tau_{_T}< \tau_{p}$, the DPL temperature has a similar thermal profile of the
Fourier heat equation, however, when $\tau_{_T}\ge \tau_{p}$ this profile is
very different from the Fourier case. Additionally, via a numerical Fourier
transform the wave-like behavior of DPL temperature is explored, and it was
found that as $\tau_{_T}$ increases, thermal wave amplitude is increasingly
attenuated. Exact solutions for pressure were compared with experimental
signals, showing a close resemblance between both data sets, particularly in
the time domain, for an appropriated value of $\tau_{_T}$; the transference
function was also calculated, which allowed us to find the maximum response in
frequency for the considered experimental setup.
