# Measure Transmission Through a Waveguide

Editor: FDTD project › Model, Setup and Results tabs · Python: td.Simulation

You get the share of the power that travels through a silicon waveguide, at each wavelength from 1.5 to 1.6 µm.

# Before You Start

  • An FDTD project with the wavelength range 1.5–1.6 µm (Setup › Configuration › Wavelength). See Create Your First Project.

Cloud only

This run costs about 0.025 FlexCredits.

# Steps

  1. Click Domain on the canvas toolbar. Set Size to 6, 3 and 2 (µm).

  2. In Model › Mediums, click +, then Material Library. Search "Silicon", pick Silicon (Crystalline) ("cSi") › Palik_NoLoss, and click OK.

  3. In Model › Structures, click +, then Box. Set Name to waveguide, Size to inf, 0.5 and 0.22, and Medium to the silicon. Click OK. With inf (Infinity), the waveguide passes through the boundaries.

    Edit Box form with Name waveguide, Size Infinity, 0.5 and 0.22, and the silicon medium

    Edit Box form

  4. In Setup › Sources, click +, then Mode Source. Set Center X to −2, and Size Y and Z to 2 and 1.5. Keep + (Forward) and Mode index 0. Click OK.

  5. In Setup › Monitors, click +, then Flux Monitor. Set Center X to 2, and Size Y and Z to 2 and 1.5. Click OK.

    The waveguide with the mode source on the left and the flux monitor on the right

    Setup tab

  6. Click Check Simulation. Wait for Validation Passed.

  7. Click Run Simulation. When the Congratulations! dialog shows, click Go To Simulation Results.

The source and the monitor use Set the range from the global wavelength, so they cover 1.5–1.6 µm without more settings.

# Check the Result

In the Results tab, open Monitor Datasets › fluxmonitor_0 › flux › Linear.

Results tab with the flux of fluxmonitor_0 plotted against wavelength, close to 1

Results tab

The flux is normalized to the power of the source, so it is the transmission. For this straight, lossless waveguide it is close to 1 at every wavelength. To see it in decibels, pick Decibels (dB).

If the check shows a warning or the run fails, see FDTD Troubleshooting.

# Related Content

← Box →