Pulse Dispersion Analyzer

The Pulse Dispersion Analyzer is a web-based quantitative calculator for analyzing ultrashort laser pulses. It allows users to define spectral properties (analytically or via file import) and observe the impact of spectral phase (Group Delay Dispersion - GDD, Third-Order Dispersion - TOD, etc.) on the temporal pulse shape, duration, and other characteristics.

Live Demo: Access the Analyzer Tool Here

Screenshot

Overview

The behavior of an ultrashort pulse is fundamentally governed by the Fourier relationship between its temporal and spectral representations. The temporal electric field, $E(t)$, can be determined from its spectral counterpart, $E(\omega)$, which is characterized by a spectral amplitude $A(\omega)$ and a spectral phase $\Phi(\omega)$.

This calculator focuses on the impact of the spectral phase, often described by a Taylor series expansion around the central angular frequency $\omega_0$:

$\Phi(\omega) = \phi_0 + \phi_1(\omega-\omega_0) + \frac{1}{2} \phi_2(\omega-\omega_0)^2 + \frac{1}{6} \phi_3(\omega-\omega_0)^3 + \dots$

Users can adjust these phase coefficients ($\phi_0, \phi_1, \phi_2, \phi_3$) and other parameters to simulate and visualize the resulting pulse characteristics. The application uses Fast Fourier Transforms (FFT) to switch between the spectral and temporal domains.

Key Features

• Flexible Spectrum Input:
  • Define analytical spectra: Gaussian or Sech²[cite: 1].
  • Import experimental data from files (CSV, TXT, DAT) with customizable parsing options (delimiter, skip rows, data transformation)[cite: 1].
  • Optional automatic cropping of imported spectra based on FWHM[cite: 1].
• Precise Spectral Phase Control: Adjust Taylor series coefficients:
  • $\phi_0$: Constant phase offset (rad).
  • $\phi_1$: Group delay (fs).
  • $\phi_2$: Group Delay Dispersion (GDD) (fs²).
  • $\phi_3$: Third-Order Dispersion (TOD) (fs³).
• Comprehensive Outputs & Visualizations:
  • Spectral Domain Plot: Intensity and phase vs. wavelength[cite: 1].
  • Time Domain Plot: Real electric field, normalized intensity, temporal phase, and instantaneous frequency vs. time[cite: 1].
  • Intensity Autocorrelation Plot[cite: 1].
• Quantitative Analysis:
  • Calculation of Full Width at Half Maximum (FWHM) for the temporal pulse intensity[cite: 1].
  • Calculation of FWHM for the intensity autocorrelation[cite: 1].
  • Display of derived effective center wavelength and bandwidth for imported spectra[cite: 1].
• Simulation Grid Control:
  • Adjustable FFT grid size (Number of points N as 2^Exponent)[cite: 1].
  • Configurable frequency window factor for FFT span[cite: 1].
• User-Friendly Interface: Interactive controls and clear presentation of results.

Technologies Used

• Backend: Python, Flask [cite: 1]
• Numerical Computation: NumPy, SciPy [cite: 1]
• Plotting: Matplotlib (server-side, rendered as images) [cite: 1]
• Frontend: HTML, CSS, JavaScript
• File Parsing: Pandas (for imported spectra) [cite: 1]

Local Installation and Running

To run the Pulse Dispersion Analyzer locally (e.g., for development or to use unlimited grid sizes for N_exponent), follow these steps:

1. Prerequisites:

   • Python 3.7+
   • pip (Python package installer)
   • git (for cloning the repository)

2. Clone the Repository: Clone the Repository:

   git clone https://github.com/visuphy/PulseDispersionAnalyzer.git
   cd PulseDispersionAnalyzer

3. Create and Activate a Virtual Environment (Recommended):

   • On macOS and Linux:

     python3 -m venv venv
     source venv/bin/activate

   • On Windows:

     python -m venv venv
     .\venv\Scripts\activate

4. Install Dependencies:

   pip install -r requirements.txt

5. Run the Local Development Server: The run_local.py script is configured to run the Flask development server.

   python run_local.py

   Open your web browser and navigate to the address provided in your terminal (usually http://127.0.0.1:8050/PulseDispersionAnalyzer/tool for the calculator or http://127.0.0.1:8050/PulseDispersionAnalyzer/ for the intro page).

   Note on Grid Size (N_exponent): The public demo server may have a limit on the N_exponent (e.g., up to 22) to conserve resources[cite: 1]. When running locally using run_local.py (which sets APP_ENV=development), this limit is removed, allowing for larger FFT grids (e.g., N_exponent > 22)[cite: 1]. Be mindful of your local machine's memory and processing capabilities for very large values.

Configuration

• Default Parameters: Default values for wavelength, bandwidth, phase coefficients, etc., are defined in app.py within the DEFAULT_PARAMS dictionary[cite: 1].
• File Uploads: Maximum file upload size is configured in app.py (app.config['MAX_CONTENT_LENGTH'])[cite: 1].
• N_exponent Limit (Production vs. Local): The app.py file contains logic to enforce a lower N_exponent limit when not in a development environment (APP_ENV is not 'development')[cite: 1]. This is bypassed when using run_local.py, which sets this environment variable appropriately[cite: 1].

Contributing

Contributions are welcome! If you'd like to contribute, please fork the repository and submit a pull request. For major changes, please open an issue first to discuss what you would like to change.

License

This project is licensed under the terms of the MIT License.

Acknowledgements

• Original Author: Hussein-Tofaili (GitHub Profile)
• This project is maintained by VisuPhy.