[Laser] different layers with different absorption coefficient

Hi, all!

I'm an old user of COMSOL but I'm now faced to with a problem.

I am usually analyzing thermal profile on two-layered skin tissues using the heat transfer model.

When setting up Q_laser as a heat source, I want to differentiate absorption coefficient in each layer.

Here is Q_laser source term:
Q0*(1-Rc)*Ac*(1/(pi*sigx*sigy))*an1(x,x0,sigx,y,y0,sigy)*exp(-Ac*abs(z))
(where, Ac is absorption coefficient)

but I could not find how to allow each layer with different absorption coefficient.

In lower version multiphysics, I did it. but now in 4.2 ver. no results.

Please can anyone help me?