In the simulation below, you can try manipulating light by changing the amplitude and phase of the different colours.
To the left are controllers for different colours. Amplitude is how much wavelength you want to use and phase is how the light is oscillating. The bottom controller changes the wavelength on all light waves. To create really short pulses, short wavelengths have to be used.
To the right, you see the result of your choices. The top window shows all the individual waves, the middle window shows how the total wave looks like, and the bottom window shows the light intensity as a function of time, along with pulse duration.