Adding a coating

Previous  Top  Next

In the final step of this first tutorial we will add a thin absorbing film to the model. The film covers the fiber and leads to absorption bands in the detector spectrum.
First we have to create a new material that is going to represent the coating. Open the list of dielectric functions and create another entry of type 'Dielectric function model'. Name it 'Absorbing molecules'. Open the corresponding window and set a Range of 2800 ... 3200 1/cm with 400 data points. Open the list of Susceptibilities. Add a contribution of type 'Dielectric background' and two harmonic oscillators. Set the parameters of these susceptibilities to the ones shown in the following dialog:

Close the list of susceptibilities and compute with the Recalc command the dielectric function called 'Absorbing molecules'. Use the command Graphics|Real part plot parameters to set the scaling of the plot similar to the following (see the graphics help to get information on the meaning of all the graphics parameters):

Close the 'Absorbing molecules' window and go back to the main window. Open the list of Interfaces and Edit the entry called 'Vacuum-fiber'. Place the cursor in line 2 (the one with the entry 'Fiber core'). Press the '+' button to create a new entry of type 'Thin film' in between the two halfspaces. Drag the 'Absorbing molecules' from the list of dielectric functions to the newly created layer. Set its thickness to 10000 (which means 10000 nanometers). The layer stack should now look like this:

Go back to the main window. Press the Parameters button and set a spectral range from 2800 to 3200 1/cm for the spectral ray-tracing. Use 50 spectral points and 100 rays per spectral point for a quick first test. Then press Simulation in the main window. Open the window that displays the detector spectrum. Try to adjust the graphics parameters to achieve a picture like this:

If you could follow the tutorial up to this point: Congratulation! You master the basic features of SPRAY. If not, save your configuration and load the configuration tu1_step8.s99 which contains the present status of the model. Inspect the settings and try to find the differences to your model in order to find out what's wrong with your parameters.