General questions about the Gaussian Beam Source

[dheligman]

Hi MEEP community,

I was recently introduced to the Gaussian Beam Source as a type of source that can be used. For this source, you can adjust different parameters such as the source dimensions, the focus, and the beam waist. I have several questions pertaining to this type of source. First, I know that the beam waist for Gaussian optics is dependent on the numerical aperture of the lens as well as the wavelength of the light. Thus, the beam waist should be dependent on the diameter at the source for a fixed wavelength and focus. I am assuming that the simulation compensates for this by adjusting the beam diameter at the source when the beam waist is specified. Is this correct? My second question is about using a custom source instead of a continuous wave source. In the MEEP documentation, it mentions that you have to specify a center frequency for the custom source when using it in the Gaussian beam source. I am not exactly sure what it means that this determines the beam's frequency. Is it that the parameters, i.e. the beam waist, etc., that you enter in for the Gaussian beam source pertain to that frequency? I am trying to simulate a pulse and keep the numerical aperture fixed (same beam diameter at the source and focus for all frequencies). Is this possible? If so, wait could I do?

Best,
Daniel