Click on the "Create Excited State Band" button to the left of the energy diagram. An excited state band appears on the diagram, and the button is replaced by a" Create Impurity State Band" button that appears directly below it. Click this button and the impurity state band will appear below the excited state band.
Use the slider at the bottom left of the screen to increase the Pumping Spectrum Energy. Observe the red marker moving along the vertical scale on the right indicating the increase in the energy on the energy level graph as you move the slider. The color of the inside of the laser changes to reflect the pumping spectrum energy. Increase the Pumping Spectrum energy with the slider until the energy is equal to the energy of the excited state band. Then release the slider and click on the" Turn on Pumping Power" button just above the Pumping Spectrum slider. You will observe the transitions occurring in the energy level diagram. Transition arrows will appear sequentially indicating the order in which various electronic transitions occur. The excited and the impurity states would get shaded dark to indicate an increase in the population of electrons in these states. Finally after the last transition is complete the spectral lines will appear in the trial spectrum just below the energy diagram and above the actual spectrum of the ruby laser. The laser too begins to glow with a color corresponding to the energy of the transition from the impurity to the ground state.
Observe the difference between the fixed real spectrum of the Ruby laser at the bottom of the screen and the trial spectrum that was created in STEP 2. To change the trial spectrum, click the "Edit Properties" button to the near the laser. You can now drag the excited and impurity state bands using your mouse cursor (which turns into a hand). After you have changed the energy levels to their desired values. Click the "Turn on Pumping Power" button. You may need to change the pumping energy on the slider at the bottom left. Observe the resulting electronic transitions similar to the ones in STEP 2, as well as the resulting trial spectrum. Repeat the process if you do not get the desired match between the trial and real spectra.Direct comments to: Chandima Cumaranatunge (programming aspects); Sanjay Rebello (physics content).