Mastering Predictability: How Optical Broadband Monitoring Enhances G&H Optical Coatings

At any of these points, the final quality of the coated product can be challenged. G&H | Artemis, the Center of Excellence in Optical Thin Film Coatings in Plymouth, United Kingdom, has built a century-long reputation for world-class thin film solutions. Committed to a continuous-improvement culture, G&H actively seeks innovative solutions to enhance quality, reduce lead times, and minimize costs. Since 2024, G&H (LON:GHH) has proactively addressed key risks in coating deposition for complex optical structures through data-driven process optimization.

“Within a deterministic approach, one looks at an operating machine as a machine. When you input the same thing, you should have the same outcome every time,” comments Reetta.“So, as long as everything is done in the same manner, you get a fairly safe predictability of results. As a process engineer, you want to avoid having unknowns change the outcome of your inspected and vetted process. But these unknowns exist, and they usually appear under the form of process variables. So, my job was to spot those inconsistencies and categorize all those different variables that could affect the quality of our optical output. The entire optimization operation was performed under the Knowledge Transfer Partnership scheme agreed upon between G&H and the University of Plymouth. This was the premise of my research work.”

Reetta started examining the different stages of thin film production. One of the items she identified early on in the analysis were the variables linked to the deposition chambers which impact the way deposition is controlled.

“Throughout my research, I observed that the deposition and design system at G&H was already highly developed – especially when comparing what we had to other leading optical systems businesses,” said Reetta. “Precision control over coating properties is a space where a lot can go wrong, and we’ve stayed out ahead of it from a technological standpoint. For example, our software is user-friendly and has been mastered by many employees placed at different management levels in the organization. This helps prevent accessibility issues for designs. Also, we have accumulated a large library of coating designs and dispersive index files throughout the years, forming a knowledge bank that facilitates the speeding up of new coating outlines. Ever since our team of experts have started working on highly sophisticated, experimentally-prone projects, we’ve been collecting data and planning how to fix the status quo to meet the demands of incoming, complex optical coatings in the most effective, client-centric manner.”

“Optical Monitoring Systems (OMS) have been developed so that it is possible to measure real-time spectral data of the coating as it is being deposited on the optical element, and this data can be used to control the process,” mentions Reetta in her scientific paper, “Eyes in the chamber – Optical broadband monitoring for optical coating”. “The basic working concept of the OMS is that a light source and a sensor are placed in the chamber with a monitor piece or a product placed between them. From this, the OMS can determine when the layer has reached the thickness required as it meets the spectral criteria set for it. This signal will then tell the coating plant to terminate the deposition of that layer and move to the next step.”

There are different types of monitoring systems for optical applications that can be taken into account for the optimization process, including:

• Fixed Monochromatic OMS - measures a single wavelength, best for simple coatings;
• Adjustable Monochromatic OMS – allows some customization but is still limited in scope;
• Broadband Optical Monitoring Systems (BBM) – measures a full spectrum, offering higher accuracy and real-time adjustments;
• Hybrid BBM System using Quartz Crystal Microbalance (QCM) - combines BBM with QCM technology for enhanced precision.

Given the increasing complexity of G&H’s optical coatings, a Broadband Optical Monitoring System has been chosen for implementation. Reetta concludes, “To get the most out of the OMS, a BBM system will give much more information and accurate detection of the cutoff point for the layers and overall performance of the coating than a monochromatic system. On more complex coatings, a monochromatic OMS measurement can get chaotic after a number of layers and the ability to detect end points for layers is lost. With a BBM, the system is looking at a full spectrum at any point in time, so it has more features to determine the state of the coating from. We are looking forward to working with this new system.”

Investing in the Future of Optical Coatings

As optical technologies continue to advance, process improvements like optical broadband monitoring become a vital investment for manufacturers. As stated in the 2023 research “Current status, challenges, and future prospects of thin film coating techniques and coating structures”: “Thin film technology has traditionally been utilised for a variety of purposes, once with aesthetics and then spreading to optics and industrial components. With the development of superior deposition methods, as well as the rapid advancement of vacuum technology and electrical power, the applications for thin film technology are practically limitless.”[2]

G&H chooses to stay ahead of the developmental curve by empowering engineers such as Reetta Griffiths to come in, analyze and improve operations. By investing in talent, technology, and processes like enterprise resource planning systems, G&H is ready to deliver high-performance optical systems that meet the industry’s most demanding specifications.

[1] Key issues of Optical thin film coating Fabrication. (2024, September 16). Retrieved February 28, 2025, from https://www.photonicsonline.com/doc/key-issues-of-optical-thin-film-coating-fabrication-0001.

[2] Sathish, M., Radhika, N., & Saleh, B. (2023). Current status, challenges, and future prospects of thin film coating techniques and coating structures. Journal of Bio-and Tribo-Corrosion, 9(2), 35.