Dear Sara,

In my modest opinion the answer to this question is no so simple. The expression you proppose, in fact, implies some sort of "balance", an stationary situation where all the energy supplied by the laser is lost in some other ways, keeping sample's temperature constant, since it doesn't express the fact that temperature raises.

A precise answer to your question needs of more information about your irradiation procedure. The time you irradiate your sample and the moment where you want to know temperature, are important. When you irradiate your sample with the laser, some energy imput (proportional to irradiation time and to the power of the laser) is given to the sample in a very localized point. There are several things that happen then: (i) part of this heat is transferred to the environment by convection, (ii) Also some heat transfer to the environment occurs by radiation (iii) part of the heat diffuses to cooler places on your sample raising the temperature in different points but not in the same way, and (iv) some other processes altering the structure of your sample may occur by absorbing some energy fron the laser. This means that "temperature" is not a fixed and homogeneous quantity, but you have some temperature profile evolving with time. It will be different in different points of your sample and it will depend on time (and on the irradiation time, as I said previously). The most precise answer is given by solving the heat equation with the appropriate boundary conditions. Even if you want to know the value of the (spatial) average of the temperaure, the answer to this question still depends on time and on the irradiation protocol. I think that you should be a little bit more precise with your question.

Best regards,

Reinaldo

No.

The distribution of energy in the surface of your sample will be complicated.

Sara, it seems to me that you would be happy if the equality E=kT is satisfied. Here E means single photon energy, of course. Indeed, the very crude estimate following from this equality, i.e. T=E/k has the sense of the maximal achieved temperature. Unfortunately, it is grossly overestimated. The absorption of a said photon and further conversion of its energy into heat is a multistage and complicated process: the "free" electrons start to move faster, the phonons are created, and so on (including reemision of other photons if only a single atom/ion has been excited by incoming photon). It's a multibody/multiparticle event. Therefore one can expect that the simple estimate may be even two orders of magnitude too high. And all this is only in addition to a simple fact, that the temperature itself is very poorly defined for systems far from equilibrium or at least from stationary state.