Adiabatic operation slope-loss algorithm (AO-SLA), how to do it: adiabatic coupling

Hi Tay,

I took the liberty of modifying your code after reviewing it, try this updated version and let me know if it works for you.

import sys sys.path.append(r"C:\Program Files\Lumerical\v241\api\python") import lumapi import numpy as np

def create_adiabatic_taper(fdtd, width_input, width_output, alpha, lambda_0, n_eff): # Define the number of segments to approximate the adiabatic taper num_segments = 100 L_i_segments = np.zeros(num_segments)

    # Widths for each section 
    widths = np.linspace(width_input, width_output, num_segments + 1)

    vertices_x = []
    vertices_y = []
    for i in range(num_segments):
        W1 = widths[i]
        W2 = widths[i + 1]
        W0 = (W1 + W2) / 2
        epsilon = 1e-10  # Small value to prevent division by zero or very small numbers
        theta = alpha * lambda_0 / (2 * (W0 + epsilon) * n_eff)

        # Prevent theta from becoming too small
        if np.abs(theta) < 1e-10:
            theta = np.sign(theta) * 1e-10

        L_i = np.abs(W1 - W2) / (2 * np.tan(theta))

        L_i_segments[i] = L_i

        if i == 0:
            vertices_x.append(0)
            vertices_y.append(W1 / 2)  # For half width
        vertices_x.append(sum(L_i_segments[:i+1]))
        vertices_y.append(W2 / 2)  # For half width

    vertices_x = np.array(vertices_x)
    vertices_y = np.array(vertices_y)

    vertices_x_full = np.concatenate([vertices_x, vertices_x[::-1]])
    vertices_y_full = np.concatenate([vertices_y, -vertices_y[::-1]])
    vertices = np.vstack((vertices_x_full, vertices_y_full)).T
    print("L_i_segments:", L_i_segments)
    print("Vertices X:", vertices_x_full)
    print("Vertices Y:", vertices_y_full)
    # Create the polygon 
    fdtd.addpoly(
        x=0,  # Center of the polygon in the x-direction
        y=0,  # Center of the polygon in the y-direction
        z=0,  # Center of the polygon in the z-direction
        vertices=vertices,  # Vertices of the polygon
        material="Si (Silicon) - Palik",
        name="adiabatic_taper_polygon"
    )
    fdtd.addtogroup("::model::Taper")

fdtd = lumapi.FDTD() fdtd.selectall() fdtd.delete()

1. Parameters for the adiabatic taper wavelength = 1550e-9 # Operating wavelength in meters width_input = 0.5e-6 # Width of the input waveguide in meters width_output = 0.075e-6 # Width of the output waveguide in meters alpha = 1 # Slope angle in degrees lambda_0 = 1550e-9 # Center wavelength in meters n_eff = 3.47 # Effective index of the cross-section at the center of the taper

1. Create the adiabatic taper create_adiabatic_taper(fdtd, width_input, width_output, alpha, lambda_0, n_eff)

Hopefully, this code should now correctly calculate the length of each segment of the adiabatic taper without producing negative values.