### Gain calculation

In the following tutorial we show that how the optical properties can be calculated for a simple nitride LED structure.

We can calculate the voltage characteristics, and the band structure with the the drift diffusion calculator, results the following band structure for the device.

The absorption, emission, gain, and spontaneous emission of the structure of the device can be calculated with consonant effective mass, or with \vec{k} space dispersion.

The gain spectrum is plotted in Figure 3. approximating constant effective mass.