Week 4: ring resonators focus + HW04 problem set

Author: rmcamacho

marimo_course.py

@@ -41,8 +41,8 @@ def _(mo):
     - **Week 3 (Jan 19–23)** – MZI verification workflow
       Local DRC/verification in KLayout; DFT and CI checks for openEBL.
 
-    - **Week 4 (Jan 26–30)** – Ring resonators + adding extra structures
-      Add rings and other useful test structures; keep a clean, probe-friendly floorplan.
+    - **Week 4 (Jan 26–30)** – Ring resonators
+      Ring resonator intuition, design knobs, and layout patterns.
 
     - **Week 5 (Feb 2–6)** – GitHub and openEBL checks
       Forking `openEBL-2026-02`, CI checks, and artifact-based debugging.

marimo_course/assignments/README.md

@@ -9,3 +9,4 @@ Assignments in this repo:
 - `marimo_course/assignments/hw02_mzi_modelling.py`
 - `marimo_course/assignments/hw02_mzi_layout.py`
 - `marimo_course/assignments/hw03_drc_debugging.py`
+- `marimo_course/assignments/hw04_ring_resonators.py`

marimo_course/assignments/hw04_ring_resonators.py

@@ -0,0 +1,235 @@
+#!/usr/bin/env python3
+# /// script
+# requires-python = ">=3.11,<3.13"
+# dependencies = [
+#   "marimo>=0.18.0",
+#   "pyzmq",
+#   "simphony==0.7.3",
+#   "jax[cpu]",
+#   "sax",
+#   "matplotlib",
+# ]
+# ///
+
+import marimo
+
+__generated_with = "0.19.6"
+app = marimo.App()
+
+
+@app.cell(hide_code=True)
+def _():
+    import marimo as mo
+    from _assignment_template import _ensure_lessons_on_path, load_lesson_template
+
+    from textwrap import dedent as _dedent
+
+    _ensure_lessons_on_path()
+    inject_css, _make_doc_helpers, _make_health_refresh_button, header = load_lesson_template()
+    inject_css(mo)
+
+    header(
+        mo,
+        title="HW04 — Ring resonators (Simphony + design)",
+        subtitle=(
+            "Simulate ring resonators, measure FSR and Q, and design an add-drop ring."
+        ),
+        badges=["Week 4", "Homework", "Rings", "Simphony"],
+        toc=[
+            ("Overview", "overview"),
+            ("Part A — Simulate 3 radii + measure FSR", "part-a"),
+            ("Part B — Design for target FSR + estimate m", "part-b"),
+            ("Part C — Add-drop ring + critical coupling + Q", "part-c"),
+            ("Part D — Layout add-drop filter + DRC", "part-d"),
+            ("Submission", "submit"),
+        ],
+        build="2026-01-28",
+    )
+
+    mo.callout(mo.md("Problem set (no solutions)."), kind="info")
+
+    mo.md(
+        _dedent(
+            r"""
+            <a id="overview"></a>
+            ## Overview
+
+            Four tasks:
+            1. Simulate a ring resonator (3 radii) and measure the FSR.
+            2. Design a ring for a target FSR and estimate the mode number near 1550 nm.
+            3. Design an add-drop ring, attempt critical coupling, and estimate Q.
+            4. Lay out an add-drop filter with grating couplers and pass DRC.
+            """
+        ).strip()
+    )
+    return mo
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            <a id="part-a"></a>
+            ## Part A — Simulate 3 radii, measure FSR
+
+            Simulate an ideal all-pass ring resonator in Simphony for three radii.
+            From the plots, measure the FSR near 1550 nm and compare to the analytic result from class.
+            """
+        ).strip()
+    )
+    return
+
+
+@app.cell
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            ### Part A deliverables
+
+            - Plot transmission vs wavelength for 3 radii.
+            - Report measured FSR for each radius.
+            - Report analytic FSR for each radius and percent error.
+
+            Helpful imports:
+
+            ```python
+            from jax import config
+            config.update("jax_enable_x64", True)
+
+            import jax.numpy as jnp
+            import sax
+            from simphony.libraries import ideal
+            import matplotlib.pyplot as plt
+            ```
+            """
+        ).strip()
+    )
+    return
+
+
+@app.cell
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            Record your results in a table (R, measured FSR, analytic FSR, percent error).
+            """
+        ).strip()
+    )
+    return
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            <a id="part-b"></a>
+            ## Part B — Design for target FSR
+
+            Pick a target FSR near 1550 nm. Choose a ring radius that meets it (first pass),
+            then estimate the mode number near 1550 nm (m).
+            """
+        ).strip()
+    )
+    return
+
+
+@app.cell
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            ### Part B deliverables
+
+            - Target FSR and chosen radius.
+            - Estimated m near 1550 nm (value + nearest integer).
+            """
+        ).strip()
+    )
+    return
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            <a id="part-c"></a>
+            ## Part C — Add-drop ring + critical coupling + Q
+
+            Design an **add-drop ring resonator** and simulate both **through** and **drop** ports.
+
+            Goals:
+            - Adjust coupling to attempt **critical coupling** (largest on-resonance extinction in the through port).
+            - Estimate the **loaded Q** from your simulated spectrum (from the linewidth).
+            - Compare your measured Q to an analytic estimate from class.
+
+            ### Part C deliverables
+
+            - Through + drop spectra for your add-drop ring (axes labeled).
+            - A short note describing how you tuned coupling and whether you achieved near-critical coupling.
+            - Q from the plot and your analytic Q estimate (with assumptions stated).
+            """
+        ).strip()
+    )
+    return
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            <a id="part-d"></a>
+            ## Part D — Layout add-drop filter + DRC
+
+            Lay out an **add-drop ring filter** with **grating couplers** (input, through, drop).
+            Export a GDS and make sure it passes all DRC checks.
+
+            ### Part D deliverables
+
+            - GDS of your add-drop filter with grating couplers.
+            - A DRC report showing 0 items.
+            - A screenshot of the layout.
+            """
+        ).strip()
+    )
+    return
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    from textwrap import dedent as _dedent
+
+    mo.md(
+        _dedent(
+            r"""
+            <a id="submit"></a>
+            ## Submission
+
+            Submit your plots/calculations (Parts A, B, C) and your layout artifacts (Part D).
+            """
+        ).strip()
+    )
+    return
+
+
+if __name__ == "__main__":
+    app.run()

marimo_course/lessons/_style.py

@@ -232,4 +232,5 @@ def header(
     </div>
     """
 
-    return mo.vstack([mo.md(hero), mo.md(toc_html)])
+    # Dedent to avoid markdown treating the HTML as a code block.
+    return mo.vstack([mo.md(dedent(hero).strip()), mo.md(dedent(toc_html).strip())])

marimo_course/lessons/w01_orientation_tooling.py

@@ -168,7 +168,7 @@ def _(date, timedelta):
         1: "Orientation and tooling",
         2: "PDKs and basic MZI layout",
         3: "MZI verification workflow",
-        4: "Routing and floorplanning",
+        4: "Ring resonators",
         5: "Submission workflow and CI checks",
         6: "Submission buffer and bridge to theory",
         7: "Waveguide fundamentals",

marimo_course/lessons/w03_verification.py

@@ -2273,7 +2273,7 @@ def _(mo, show_klayout):
     mo.md(r"""
     ### What's Next
 
-    - **Week 4**: Advanced layout techniques and routing discipline
+    - **Week 4**: Ring resonators
     - **Homework**: Implement the verification workflow on your own MZI design
     - **Resources**:
         - [SiEPIC-EBeam PDK Documentation](https://github.com/SiEPIC/SiEPIC_EBeam_PDK)