Slab Junctions

Tools for designing and fabricating superconducting Josephson junctions using e-beam lithography.

Overview

This repository provides Python tools for:

• Dose chip generation: Create comprehensive test chips with dose and geometry sweeps
• Junction design: Multiple junction types (Dolan, Manhattan cross, arrays)
• phidl integration: Modern GDS layout generation using the phidl library

Features

Dose Chip Generator

• Create 5×5 mm or 7×7 mm dose test chips
• Dose tests: Vary e-beam doses with fixed geometry
• Geometry sweeps: Vary junction dimensions with fixed doses
• Manhattan junction support
• Automatic dose tables for BEAMER e-beam system
• Configurable grid layouts

Junction Types

• Dolan junctions: Standard bridge junctions with undercut
• Manhattan cross junctions: Perpendicular crossing leads with paddle undercuts
• Junction arrays: Multiple junctions in series
• Asymmetric junctions: Different widths on left/right sides

phidl Bridge

• Compatibility layer between old mask_maker API and modern phidl
• Stateful CPW drawing (CPWStraight, CPWLinearTaper, CPWBend)
• Two-layer support (PIN/GAP for optical/e-beam lithography)

Installation

Requirements

• Python 3.8+ (tested with Python 3.10)
• phidl (GDS layout library)
• numpy (numerical computing)
• shapely (polygon operations)
• Optional: jupyter, matplotlib (for interactive notebooks)

Quick Setup (Recommended)

Option 1: Using conda (Recommended)

# Create a new environment
conda create -n slab_junctions python=3.10 -y

# Activate the environment
conda activate slab_junctions

# Install dependencies
pip install -r requirements.txt

# Test the installation
python test_installation.py

Option 2: Using pip

# Create a virtual environment (optional but recommended)
python -m venv venv
source venv/bin/activate  # On Windows: venv\Scripts\activate

# Install dependencies
pip install -r requirements.txt

# Test the installation
python test_installation.py

Verification

After installation, run the test script to verify everything works:

python test_installation.py

You should see output like:

======================================================================
SLAB JUNCTIONS - INSTALLATION TEST
======================================================================

[OK] Imports: PASSED
[OK] phidl_bridge: PASSED
[OK] Dose Chip Generator: PASSED
[OK] Junction Functions: PASSED

[OK] ALL TESTS PASSED!
The slab_junctions package is working correctly.

Quick Start

1. Generate a Dose Chip

from dose_chip.dose_chip_generator import DoseChipGenerator, draw_dolan_junction

# Create 5×5 mm chip
generator = DoseChipGenerator(chip_size=(5000, 5000))

# Add dose test grid (vary doses)
generator.add_dose_test(
    name='Dose Test',
    junction_func=draw_dolan_junction,
    geometry=(0.2, 0.2),  # Fixed width, gap
    dose_fullcut_range=(400, 3600),
    dose_undercut_range=(100, 1200),
    position=(-2350, 1017),
    n_rows=15,
    n_cols=15,
    spacing=100
)

# Save GDS and dose table
generator.save('my_chip.gds')

2. Design Custom Junctions

See junction_experiments/ for interactive notebooks and examples:

• test_manhattan_junction.ipynb: Manhattan cross junction designer
• examples/asymmetric_junction.py: Asymmetric junction example
• templates/template_array.py: Junction array template

Documentation

phidl_bridge User Guide

Comprehensive guide to using the phidl_bridge API for CPW layout design:

📖 PHIDL_BRIDGE_GUIDE.md

Covers:

• Common functions: CPWStraight, CPWLinearTaper, CPWBend
• CPW geometry convention: Understanding pinw/gapw parameters
• Layer management: Single and two-layer modes for optical/e-beam
• Complete examples: Lines, bends, tapers, junctions, meanders
• Best practices: Tips and troubleshooting

Perfect for learning how to create custom CPW structures!

Repository Structure

slab_junctions/
├── README.md
├── requirements.txt
├── .gitignore
├── phidl_bridge.py          # phidl compatibility layer
├── phidl_native.py           # Native phidl components
├── dose_chip/
│   ├── dose_chip_generator.py  # Main dose chip library
│   └── my_chip_config.py       # Example configuration
├── junction_experiments/
│   ├── test_manhattan_junction.ipynb  # Interactive junction designer
│   ├── examples/
│   │   └── asymmetric_junction.py
│   └── templates/
│       └── template_array.py
└── examples/
    └── run_files.ipynb          # Full workflow example

Usage Examples

Dose Test (Vary Doses)

generator.add_dose_test(
    name='My Dose Test',
    junction_func=draw_dolan_junction,
    geometry=(0.2, 0.2),
    dose_fullcut_range=(500, 2000),
    dose_undercut_range=(100, 600),
    position=(0, 0),
    n_rows=10,
    n_cols=10,
    spacing=100
)

Geometry Sweep (Vary Dimensions)

generator.add_dose_array(
    name='Geometry Sweep',
    junction_func=draw_dolan_junction,
    dose_fullcut=1450,
    dose_undercut=350,
    width_range=(0.1, 0.4),
    gap_range=(0.1, 0.4),
    position=(0, 0),
    n_rows=10,
    n_cols=10,
    spacing=100
)

Manhattan Junction

generator.add_manhattan_dose_test(
    name='Manhattan Test',
    geometry=(0.18, 0),
    dose_fullcut_range=(400, 3600),
    dose_undercut_range=(100, 1200),
    position=(0, 0),
    n_rows=15,
    n_cols=15,
    spacing=100
)

Layer Convention

• Layer 1: Optical lithography labels and markers
• Layer 2: Clearing dose text (3000 µC/cm²)
• Layer 20: E-beam fullcut (PIN layer - junction metal)
• Layer 60: E-beam undercut (GAP layer - junction bridge)
• Layers 200-214: Dose test fullcut layers (varying doses)
• Layers 600-614: Dose test undercut layers (varying doses)

Fabrication Notes

E-beam Doses

• Fullcut doses typically range from 400-3600 µC/cm²
• Undercut doses are multiplied by 4× for BEAMER compatibility
• Clearing dose for text labels: 3000 µC/cm²

Geometry

• Minimum junction width: ~0.05 µm (50 nm)
• Typical undercut border: 0.15-0.3 µm (150-300 nm)
• Grid spacing: 50-500 µm depending on chip size

Contributing

This is a research tool developed at the Schuster Lab. For questions or contributions, please contact the maintainers.

License

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Citation

If you use this code in your research, please cite: [Add citation information]