8-Channel mode and polarization de-multiplexer¶

Note: the cost of running the entire notebook is larger than 1 FlexCredit.

Mode-division multiplexing and polarization-division multiplexing on integrated photonic circuits are critical for large-bandwidth and high-speed optical communication networks. Here we introduce an 8-channel mode and polarization (de)multiplexer that is based on asymmetric directional couplers that operate on TE0 to TE3 as well as TM0 to TM3 modes. The design is based on Wang, J., He, S. and Dai, D. (2014), On-chip silicon 8-channel hybrid (de)multiplexer enabling simultaneous mode- and polarization-division-multiplexing. Laser & Photonics Reviews, 8: L18-L22.

The notebook is organized as the following:

First, we use Tidy3D's ModeSolver to simulate the effective indices of the eight modes as a function of waveguide width. From the result, we can obtain the width of the bus waveguide in each directional coupler section to satisfy the phase match condition.

Then, we model each directional coupler section individually to ensure good mode conversion efficiency.

Lastly, once we confirm that good performance is achieved on each section, we build the whole 8-channel (de)multiplexer and simulate the whole device, which is about 200 $\mu m$ in length. Thanks to the fast speed of Tidy3D solver, large simulations like these can be handled easily.

The models in this notebook contain many waveguide bends. These bends can be defined natively in Tidy3D as demonstrated in the Euler waveguide bend example or the waveguide Y junction example. Alternatively, it is often easier to make use of gdstk as shown in the GDSII import tutorial. Here we will also demonstrate how to use gdstk to define the structures used in the simulation.