Usually the simulation volume should be larger than the device, except to use PML/peridoic BCs to truncate the device in purpose, such as infinitely large.
You can find TE00 based on the TE polarization value, and also should be aware that TE/TM has two differfent definitions.
A1: FDE is to analyze the mode properties, and FDTD has mode source/Port that uses FDE. So FDTD can be used to simulate waveguide devices
A2: In FDTD, you can get the loss from a mode source or port. or
you can set to use "user select" in "mode selection" and click "select mode", then the FDE interface will open
A3: please visit https://optics.ansys.com/hc/en-us/articles/360034917493-Working-with-lossy-modes-and-dB-m-to-kappa-conversion
A4: you have to create the bending waveguide first. Please refer the object library for "integrated optics". If you create your own, you may need to learn how to use the structure group, and script.
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