GCSlab

Quickly estimate the directionality of a grating coupler using a homogenized-slab model.

Prerequisites

Before using GCSlab, the following python libraries must be installed:

• numpy
• Matplotlib

Furthermore, currently gcslab only supports python3.

Example

The following code snippet models a simple partially-etch silicon grating coupler. The grating coupler is defined by stacking up slabs of different refractive index. The etched region of the grating is assigned an average refractive index and a non-zero source amplitude. In this region, waves are injected and the total fraction of power leaving the top of the grating is estimated.

import gcslab
import numpy as np
from math import pi

grating = gcslab.GCSlabModel()

# Define useful parameters
wavelength = 1.55
angle = 8.0/180*pi

n_Si = 3.45
n_SiO2 = 1.44

h_Si = 0.22
h_etch = 0.11
h_BOX = 2.0
df = 0.8

# Build the grating layer-by-layer. For each layer, we specify the thickness
# and refractive index. At least one layer must also have a non-zero source
# amplitude assigned to it
grating.add_slab(np.inf, n_SiO2)
grating.add_slab(h_etch, n_Si*df + n_SiO2*(1-df), source_amplitude=1.0)
grating.add_slab(h_Si-h_etch, n_Si)
grating.add_slab(h_BOX, n_SiO2)
grating.add_slab(np.inf, n_Si)

# Visualize the layer stack
grating.visualize_stack() 

# Calculate the directionality
directionality = grating.directionality(wavelength, angle)
print(f'The directionality = {directionality}.')

This example can be found in the example_gc.py.

Citing this Code

This code is based on the doctoral thesis titled "A Hierarchical Approach to the Design and Optimization of Photonics." If using this code in a publication, please reference the afformentioned work.