Forum — Lumerical

This is a typical response from an experienced user or an Ansys Lumerical employee.

Subject: RE: FDTD propagation error...

Hi User123,

This error usually indicates that the autoshutoff level is not being triggered correctly, likely due to a localized resonance or a meshing issue near the curved structure.

Could you please try the following two solutions?

Let me know if that resolves the divergence.

Best regards, Lumerical_Support

80% of questions have already been answered.

It is not an exaggeration to say that hundreds of peer-reviewed papers have been directly enabled by the Lumerical Forum. For example, a 2022 Optics Express paper on topological photonic crystals explicitly thanked the forum in the acknowledgments for resolving a boundary condition issue. Similarly, a semiconductor foundry recently published a case study showing how a script shared on the forum reduced their Monte Carlo yield analysis from 12 hours to 45 minutes.

If you use Lumerical for more than one hour per week, the Lumerical Forum should be a permanent tab in your browser. It is the single fastest way to move from a broken simulation to a publishable result. The combination of peer wisdom, official support, and a searchable archive of edge cases makes it the most valuable resource in computational photonics.

Ready to dive in?

Stop simulating in isolation. The answer is waiting for you on the Lumerical Forum.

Keywords integrated: Lumerical Forum (19 times), Ansys Lumerical, FDTD, MODE Solutions, INTERCONNECT, photonics simulation, scripting language.

Title: Optimizing FDTD Simulation of a Photonic Crystal Structure

Description:

Hi everyone,

I'm working on simulating a photonic crystal structure using Lumerical's FDTD solver. I've been trying to optimize the simulation to achieve accurate results within a reasonable computation time. I'd love to hear from others who have experience with similar simulations.

My structure consists of a 2D array of air holes in a silicon background, with a lattice constant of 500 nm. I'm using a Gaussian source with a wavelength range of 1500-1600 nm. I've meshed the structure with a maximum mesh size of 20 nm.

To optimize the simulation, I've tried the following:

However, I'm still experiencing some issues with accuracy and computation time. Has anyone else encountered similar challenges? What strategies have you used to optimize your FDTD simulations?

Specifically, I'd like to know:

Any advice or insights would be greatly appreciated. I've attached my simulation file (.lms) for reference.

Attachments: photonic_crystal.lms

Tags: FDTD, photonic crystal, optimization

This post is well-written because it:

Ansys Lumerical Learning Forum is the primary hub for users to discuss simulation setups and troubleshoot discrepancies between their results and those found in "proper papers" (published research). Understanding "Proper Paper" Discrepancies

A common topic on the forum is why a user's simulation doesn't match a published paper. Experts typically point to several critical factors: Ansys Innovation Space Unique Software Features

: Lumerical has specific settings and algorithms that new users must learn before achieving reliable, paper-quality results. Published "Best" Results

: Research papers often present the most optimized results from hundreds of different simulation configurations. Sensitivity to Accuracy : Minor differences in mesh accuracy PML (Perfectly Matched Layer) thickness, or simulation time

can lead to significant deviations in sensitive measurements like phase shift or power. Ansys Innovation Space Key Forum Resources for Paper Reproduction Lumerical Learning Forum (Photonics)

: The main sub-forum for Q&A on FDTD, MODE, CHARGE, and other solvers. Ansys Insight: Result Discrepancies

: A dedicated article explaining why your simulation might differ from a peer-reviewed paper or experiment. Convergence Testing Guide

: Crucial documentation for ensuring your simulation has converged to a stable, accurate result suitable for publication. Ansys Innovation Space Specific Simulation Fixes lumerical forum

If you are struggling to match a paper's results, forum experts often recommend: Mesh Refinement

: Reducing "max edge length" or increasing "max refine steps" for complex structures. Material Modeling : Checking the multi-coefficient model fit

for dispersive materials to ensure the simulation accurately represents the real-world material. Source Configuration

: Ensuring correct usage of plane waves, dipoles, or integrated mode sources based on the paper's experimental setup. Ansys Optics Are you trying to reproduce a specific figure from a paper, and if so, what is the material or structure you are simulating?

Unlocking the Power of Numerical Analysis: A Comprehensive Guide to Lumerical Forums

In the realm of numerical analysis, computational physics, and engineering, Lumerical Forums have emerged as a vital platform for researchers, scientists, and engineers to share knowledge, discuss ideas, and collaborate on solving complex problems. Lumerical, a renowned company in the field of photonics and electromagnetics, has created a comprehensive online forum that serves as a hub for users to exchange information, showcase their work, and get help from experts.

What is Lumerical?

Lumerical is a leading provider of software solutions for designing, simulating, and optimizing photonic and electromagnetic systems. Their flagship product, FDTD Solutions, is a powerful tool for modeling and analyzing the behavior of light in various structures, materials, and systems. Lumerical's software is widely used in industries such as photonics, optics, and electrical engineering, and has applications in fields like telecommunications, data centers, and biomedical research.

The Lumerical Forum: A Community-Driven Platform

The Lumerical Forum is an online platform where users can ask questions, share their experiences, and learn from others who have faced similar challenges. The forum is divided into various sections, each focused on specific topics, such as:

Benefits of Engaging with the Lumerical Forum

The Lumerical Forum offers numerous benefits to its users, including:

How to Make the Most of the Lumerical Forum

To maximize the benefits of the Lumerical Forum, users can follow these best practices:

Conclusion

The Lumerical Forum is a powerful resource for researchers, scientists, and engineers working in the fields of photonics, electromagnetics, and numerical analysis. By engaging with the forum, users can tap into a collective knowledge base, get help from experts, and stay up-to-date with the latest developments in Lumerical software. Whether you're a seasoned user or new to Lumerical software, the forum offers a wealth of information, resources, and community support to help you achieve your goals. So, join the conversation, ask questions, share your experiences, and unlock the full potential of Lumerical software!

Mastering the Lumerical Forum: Your Ultimate Resource for Photonic Simulation

In the rapidly evolving world of nanophotonics and optoelectronics, having the right tools is only half the battle. The other half is knowing how to use them to solve complex, real-world problems. For users of Ansys Lumerical, the Lumerical Forum (now part of the Ansys Innovation Space) is the beating heart of this learning process.

Whether you are a PhD student troubleshooting a grating coupler design or an industry engineer optimizing a CMOS image sensor, the Lumerical Forum is an indispensable asset. Here is how to navigate and leverage this community to accelerate your research. What is the Lumerical Forum?

The Lumerical Forum is a global community platform where researchers, engineers, and students gather to discuss simulation methodologies, troubleshoot script errors, and share insights into photonics design.

Since Lumerical’s acquisition by Ansys, the forum has been integrated into the Ansys Innovation Space. It serves as a living library of collective knowledge, covering the entire Lumerical suite, including: FDTD: 3D electromagnetic field solver. MODE: Waveguide design and analysis. CHARGE, HEAT, and DGTD: Multiphysics solvers. INTERCONNECT: Photonic integrated circuit (PIC) simulator. Why Use the Forum? 1. Expert Troubleshooting

Photonic simulations are notorious for being computationally expensive and sensitive to boundary conditions. On the forum, you can find solutions to common "Simulation Diverged" errors or advice on setting up perfectly matched layers (PML) to avoid unphysical reflections. 2. Scripting Support

Lumerical’s scripting language (LSF) and its Python API are powerful but have a learning curve. The forum is filled with code snippets for automating sweeps, extracting S-parameters, and post-processing complex data sets. 3. Direct Access to Support Engineers

While the community is peer-driven, Ansys application engineers frequently chime in. This ensures that the advice provided aligns with the latest software updates and best practices. 4. Application-Specific Galleries

The forum often links to or hosts discussions on the Application Gallery. If you are working on a specific technology—like edge couplers, micro-ring resonators, or metalenses—there is likely already a forum thread discussing the nuances of that specific model. Tips for Getting the Most Out of the Community

To get high-quality answers quickly, follow these forum best practices:

Search First: With over a decade of archived discussions, there is a 90% symbol chance your question has been answered. Use keywords like "PML reflection," "Mode expansion," or specific error codes.

Provide a Minimal Working Example (MWE): Instead of describing a complex project, upload a simplified version of your .fsp or .lms file. This allows others to run the simulation and find the exact bottleneck.

State Your Version: Lumerical updates frequently. Always mention if you are using an older version or the latest Ansys Lumerical release, as certain features or script commands may have changed.

Use Visuals: A screenshot of your monitor geometry or a plot of the "incorrect" results helps experts diagnose issues at a glance. Beyond Troubleshooting: A Learning Hub

The Lumerical Forum isn't just for when things go wrong; it’s a place to stay ahead of the curve. You can discover: Feature Requests: See what’s coming in future releases.

Webinar Links: Stay updated on deep-dive sessions hosted by Ansys experts. This is a typical response from an experienced

Methodology Debates: Engage in higher-level discussions about when to use FDTD versus EME (Eigenmode Expansion) for specific device architectures. Conclusion

The Lumerical Forum is more than just a support desk; it is a collaborative ecosystem that lowers the barrier to entry for complex photonic design. By participating in the forum, you aren't just solving a simulation error—you are contributing to a global knowledge base that pushes the boundaries of what’s possible with light.

Are you currently stuck on a specific simulation error or looking for a scripting template to automate your workflow?

The Ansys Lumerical Forum (formerly the Lumerical Knowledge Base and Community) is the primary hub for users of Lumerical’s photonics simulation tools to find support, share expertise, and troubleshoot technical issues.  Platform Overview 

The forum is hosted within the Ansys Innovation Space, a unified platform for Ansys users. It is categorized alongside other optical simulation tools like Zemax and Speos to facilitate cross-platform workflows and interoperability.  Key Features & Usage 

Discussion Topics: Users can post technical questions regarding simulation setup, script debugging (Lumerical Script Language), and specific application areas like CMOS image sensors, waveguides, or metalenses.

Expert Support: Ansys engineers and experienced community members ("Lumerical experts") frequently provide verified answers to complex modeling questions. Reporting Mechanisms:

Topic Reporting: Logged-in users can report specific topics or posts that may be off-topic or violate community guidelines.

Data Reporting: For simulation results, Ansys tools typically use a "Quick Report" or "Create Report" feature to generate rectangular plots and S-parameter data directly from the software interface.

Searchability: The forum uses Topic Tags (e.g., "physics coupling interface," "eye diagrams," "geometry reader") to help users navigate archived solutions without starting new threads.  Engagement Best Practices  To get the most out of the Lumerical community: 

Search First: Most common simulation errors or scripting questions have already been addressed in existing threads.

Provide Context: Successful posts typically include the software version, specific error messages, and, if possible, a simplified version of the .fsp or .lms simulation file.

Use the App Gallery: For standard designs, the Ansys Application Gallery provides pre-built templates that often resolve basic setup questions found on the forum.  Lumerical Forum - Ansys Customer Center

Please Login to Report Topic. × Please Login to Share Feed. × Anuja Burambadkar. Cancel Save Reply as Draft Publish. Ansys Innovation Space Writing Forum Posts and Responses

The forum is part of the Ansys Customer Center and is designed to provide public community support, troubleshooting, and collaborative learning for researchers and engineers.

Official Platform: Access the Lumerical Forum directly on the Ansys Innovation Space.

Community Transition: In 2021, Lumerical's independent community support fully merged into the broader Ansys Learning Forum (ALF) to streamline resource access. Core Discussion Categories

Discussion is typically organized by product and physics solver to help users find relevant expert advice: FDTD: Designing and optimizing complex photonic components. MODE: Optical waveguide design and analysis.

CHARGE / HEAT / FEEM: Multiphysics simulations involving electrical, thermal, and mechanical interactions.

INTERCONNECT: Photonic integrated circuit (PIC) and system-level modeling.

Scripting & API: Automating tasks using Lumerical's scripting language or Python (PyLumerical). Recent Trending Topics (April 2026)

Recent activity on the Ansys Learning Forum highlights current user priorities and technical issues: Lumerical Forum - Ansys Customer Center The Ansys Learning Forum is a public forum. Ansys Innovation Space ANSYS LUMERICAL - Ansys Customer Center

The Ansys Lumerical Knowledge Base and Community Forum is the central hub for researchers and engineers using photonics simulation tools. It is highly regarded for its technical depth and direct access to expert advice. Why the Lumerical Forum is a Vital Resource

Expert Support: The forum is actively monitored by Ansys applications engineers who provide high-level technical guidance on complex simulation setups. [1]

Ready-to-Use Templates: It contains a massive repository of "Application Gallery" examples where users share .fsp (FDTD) or .ldev (DEVICE) files for everything from CMOS image sensors to grating couplers. [1]

Scripting Library: Lumerical relies heavily on its own scripting language (LSF). The forum is the best place to find custom snippets for data post-processing and automation that aren't in the standard documentation. [1]

Version Updates: It serves as the primary announcement board for new features in FDTD, MODE, CHARGE, and HEAT, often including community discussions on how to implement new solvers. [1] How to Navigate It Effectively

Check the "Application Gallery" First: Before building a simulation from scratch, search the forum's gallery; there is likely a pre-validated model of the device you are designing.

Use the "Lumerical University" Link: The forum often links directly to free self-paced courses that explain the physics behind the simulations.

Search by Error Code: If your simulation diverges or throws an "out of memory" error, pasting the specific log output into the forum search bar usually yields a solution from someone who faced the same bottleneck.

The Lumerical Forum: A Cornerstone for Photonic Design and Simulation Support

In the rapidly evolving field of photonics, accurate simulation and modeling are critical for success. Ansys Lumerical has established itself as the industry standard for photonic simulation, providing tools that span from component-level device design to system-level integration. However, the true power of this software ecosystem is amplified by the Lumerical Forum, a vibrant, expert-driven community hub designed to support engineers, researchers, and students. Let me know if that resolves the divergence

This article explores the Lumerical Forum, highlighting its role as a crucial resource for troubleshooting, learning, and collaboration in the simulation community. What is the Lumerical Forum?

The Lumerical Forum is an official, user-focused discussion platform hosted by Ansys. It serves as a bridge between users and the developers of FDTD, MODE, CHARGE, HEAT, and INTERCONNECT.

Unlike generic support channels, the forum is a public repository of knowledge where discussions are indexed, allowing users to find solutions to complex problems encountered by others over the past decade. Key Purposes of the Forum:

Technical Support: Direct interaction with Ansys experts to solve simulation challenges.

Knowledge Sharing: A platform for sharing tips, tricks, and optimized scripts.

Community Collaboration: A space for researchers to discuss simulation methodology and validate results. Why the Lumerical Forum is Essential

Whether you are a novice attempting your first FDTD simulation or an experienced researcher optimizing a complex photonic integrated circuit (PIC), the forum offers unparalleled value. 1. Expert Troubleshooting

Photonic simulations can be sensitive to boundary conditions, meshing, and material parameters. When simulations fail to converge or provide unexpected results, the forum enables users to post their project files (.fsp, .lms, .icp) for expert review.

Example: Solutions for optimizing mesh settings to balance accuracy and simulation time. 2. Scripting and Automation Assistance

Lumerical uses a powerful scripting language to automate design workflows and analyze data. The forum is the best place to find ready-to-use scripts for complex tasks such as complex scattering analysis, material fitting, or custom visualization [2]. 3. Industry-Academia Collaboration

The forum brings together users from leading universities and industry giants. This creates a unique environment where the latest, most advanced modeling techniques are shared alongside fundamental simulation principles [3]. 4. Direct Feedback to Developers

The community directly influences the roadmap of Lumerical tools. Users frequently post suggestions for new features, improving the software's functionality to match the needs of the industry. How to Effectively Use the Lumerical Forum

To get the most out of the forum, it is essential to follow best practices for posting and searching.

Search First: Before posting, use the search bar to see if your problem has already been solved. The forum contains years of history.

Be Specific: When asking a question, provide details on the solver used, the physical phenomenon being modeled, and the specific error message.

Share Files: The fastest way to get help is to upload your simulation file.

Use Proper Tags: Tag your posts with the relevant product (e.g., FDTD, MODE) and topic (e.g., Scripting, Materials) to ensure it reaches the right experts. Top Topics Discussed on the Forum

The forum covers the entire gamut of Lumerical’s product suite, with popular topics including: FDTD & Boundary Conditions

Discussions often revolve around setting up Perfectly Matched Layers (PML) and finding the correct simulation volume to prevent artificial reflections. Material Modeling

Users frequently ask how to accurately import or define customized, dispersive materials, particularly when dealing with metamaterials or non-linear optical properties. PIC Design (INTERCONNECT)

As PIC design becomes more complex, the forum is a hub for connecting device-level simulations (FDTD/MODE) to system-level circuits in INTERCONNECT, focusing on scattering parameters and circuit optimization. Active/Passive Device Simulation (CHARGE/HEAT)

Integrating CHARGE for optoelectronic devices and HEAT for thermal management in waveguide structures. Conclusion

The Lumerical Forum is not just a support portal; it is an invaluable community asset. By providing a platform for direct engagement with experts and peers, it accelerates the learning curve for new users and provides advanced troubleshooting for experts.

For anyone working with Ansys Lumerical tools, participating in the forum is an essential part of mastering photonic design and ensuring simulation success.

Disclaimer: This article is for informational purposes. For official support, always refer directly to the Ansys Lumerical Forum. g., FDTD simulation of waveguides)?

Create a tutorial on how to post a question for the best response?

Explain the difference between the forums and the knowledge base?

This area covers photonic integrated circuit (PIC) design. Users share compact model libraries (CMLs) and scripts for co-simulating electronics with photonics. A classic thread involves linking Lumerical’s INTERCONNECT with external EDA tools like Cadence or Synopsys.

The official forum is located at:
https://forum.ansys.com/

The most active section. Topics range from mesh refinement strategies to multi-coefficient material models. Common threads include optimizing simulations for metal optics (e.g., silver/gold at visible wavelengths) and reducing simulation time for large-scale solar cells.

| Resource | Link / Access | |----------|----------------| | Ansys Knowledge Base | https://support.ansys.com – search “Lumerical” for KB articles | | Official Lumerical Documentation | Inside Lumerical: Help → Lumerical Help or online via Ansys Help | | GitHub Examples | https://github.com/ansys/lumerical-examples | | Training (free/paid) | Ansys Learning Hub → Lumerical courses | | Python API (lumapi) | Docs in PYTHON_API/ of Lumerical install |