The FREQUENCY ANALYSIS tab is shown in the screenshot below, where the various components of this tab are labeled for future reference.

For a step-by-step tutorial of an Eigenmode solver example, please see the video in Eigensolver Analysis.

### Options pull-down menu

- set parameters for running a FREQUENCY SWEEP
- export modal data that was calculated by using the "set calculation parameters" option

The option settings section of the modal analysis tab will change depending on which option was chosen in the pull down menu. The mode and frequency plot window shows the mode data for the current mode in the frequency sweep and a mode which was selected from the mode list.

### Mode plot and Frequency plot

You can control various options of the frequency sweep plot, or the mode plots (initial plot and current plot) by selecting various options. The mode plot options are the same as in the Modal analysis tab, and the frequency plot options are as follows.

The plot pull down box allows the user to choose which data to visualize. The screenshot below shows the different ways in which the simulation data can be plotted. Data which can be plotted versus wavelength or frequency include:

- EFFECTIVE INDEX: selecting this option will generate a plot of the effective index for each calculated mode, plotted as a function of wavelength or frequency.
- LOSS: selecting this option will generate a plot of the modal loss as a function of frequency. Measured in units of dB/mm of propagation.
- GAIN: selecting this option will generate a plot of the modal gain as a function of frequency. Measured in units of dB/mm of propagation.
- GROUP INDEX: Is the ratio of the speed of light to the group velocity, c/vG. Unitless.
- GROUP VELOCITY: Is defined vG = dw/db, and can be interpreted as the rate at which the peak of a temporal pulse will propagate in the absence of nonlinearities. Measured in meters per second (m/s).
- GROUP DELAY: Is defined as t = 1/vG. Measured in picoseconds per kilometer.
- DISPERSION: Is defined as the rate of change of the group delay with respect to wavelength (dt/dl). Measured in picoseconds per nanometer per kilometer (ps/(nm km)).
- BETA: Defined as b = 2p nEFF / lo, where nEFF is the effective index, and lo is the free-space wavelength. Measured in units of inverse meters (1/m).

An example running frequency analysis using parameter sweep and script, please see Sweep analysis for dispersion.