Index Grading

• Assume that SiC on Si was measured, and saved as SiC_on_Si.dat.
• The MSE is improved by incorporating index grading, as shown below.

Contents 

1 Load File

2 Build up the model layer

2.1 Si_jaw

2.2 Cauchy.mat

3 Normal Fit 1

4 Convert to Simple Index Grading

5 Normal Fit 2

1. Load File

1. Load SiC_on_Si.dat in the "Experimental" window.

2. Build up the model layer

2.1 Si_jaw

1. Click on the "Model" window to popup the menu.

2. Click the "AddLayer" from the menu or the drop-down menu popped up by right-clicking on the window.

3. Choose "Si_jaw.mat" from the file directory, as the Si substrate.

4. The "Layer" dialog box appears. Click "OK".

6. The Si substrate is shown in the "Model" window.

2.2 Cauchy.mat

1. Click the "AddLayer" again from the menu or the drop-down menu popped up by right-clicking on the window.

2. Open cauchy.mat.

3. Cauchy Layer window appears.

4. Make sure that k amplitude is zero, because no absorption is assumed.

5. Check fit boxes of "Thickness", "An", and "Bn", and click "OK".

3. Normal Fit 1

1. Select range in the "Experimental" window.

• In this case, only 75 degree data is selected.

2. Right-click on the Fit window to pop-up the menu.

3. Click the "Normal Fit" in the Fit window. Make sure that the MSE is the reasonable number (10-20).

4. Put the range back.

5. Click the "Normal Fit" in the Fit window.

6. Cauchy model fitting is shown below.

• The MSE is 14.72.

4. Convert to Simple Index Grading

1. Right-click on the cauchy layer to popup the menu.

2. Choose "Convert to Simple Index Grade".

3. The following dialog box appears.

4. Check the fit boxes of Thickness, %Variation Range, and Symmetric Profile, if necessary.

5. Click "OK".

6. The model layer structure is changed in the following:

5. Normal Fit 2

1. Right-click on the Fit window to pop-up the menu.

2. Click the "Normal Fit" in the Fit window.

3. The MSE becomes 9.6.