Photonics Essentials: Chapter 3 Interactive Physics Lab

This lab turns the equations in Chapter 3, Photodiodes, into curves that can be changed directly in the browser. It complements the Photonics Essentials: From Diffusion Current to Equation 3.5 derivation.

Important

The controls below use ideal equation-based models. The modes labelled qualitative reproduce a measured curve’s physical trends, not the book’s experimental data. Use a manufacturer’s data sheet for device design.

Interactive curve explorer

Choose a curve, then move any slider. The graph and calculated quantities update immediately; no Python server is required, so this works on the GitHub-hosted documentation.

Loading the Chapter 3 curve explorer...

Curves and equations

The explorer includes:

Explorer mode	Chapter reference	What changes
Carrier profile	Equations 3.5–3.11	Diffusion coefficient, lifetime, junction concentration, generation
Junction bands	Figure 3.1	Built-in voltage and depletion width
Photodiode I–V family	Figures 3.2–3.4; Equations 3.14 and 3.16	Temperature, ideality factor, dark current, illumination
LED semilog I–V	Figure 3.5; Equation 3.16	Temperature, ideality factor, saturation current
Ideal spectral cutoff	Figure 3.6; Equations 3.19–3.21	Band-gap energy
Rounded detector response	Figure 3.7	Short and long absorption edges; qualitative model
Absorption with depth	Figure 3.8; Equation 3.22	Absorption coefficient
Responsivity	Figure 3.9; Equations 3.25–3.28	Quantum efficiency and band gap
Antireflection response	Figure 3.10; Equations 3.29–3.32	Film index, substrate index, thickness, design wavelength, and a qualitative collection envelope at the band-gap edge
Open-circuit photovoltage	Equation 3.18	Temperature, ideality factor, and optical generation

Python physics engine

The browser controls and the notebook use the same equations implemented in KrakenOS/Physics/photodiode.py. Its primary entry points are:

from KrakenOS.Physics.photodiode import (
    PhotodiodeParameters,
    excess_carrier_profile,
    photodiode_current_density,
    photovoltage,
    responsivity,
)

parameters = PhotodiodeParameters(
    diffusion_cm2_s=25.0,
    lifetime_s=1e-6,
    temperature_k=300.0,
)

current = photodiode_current_density(
    [-0.5, 0.0, 0.5],
    parameters=parameters,
    generation_cm3_s=2.5e11,
)

Live Jupyter kernel

The button opens a real JupyterLite notebook backed by a Python kernel compiled for the browser with Pyodide. It runs locally on the reader’s computer; GitHub Pages only serves static files. The first kernel start can take several seconds because the browser downloads Python and NumPy.

The notebook is intentionally separate from the instant slider explorer: the explorer is fast and works without a kernel, while the notebook exposes the Python equations for modification and further experiments.