The field of optics has long relied on traditional materials like germanium for a range of applications, from infrared imaging to spectroscopy. However, recent challenges stemming from germanium export restrictions in China have sparked a search for alternative materials. In this article, we delve into the emergence of Chalcogenide materials as a strategic response to these constraints, exploring their unique advantages, applications, and contributions to the future of optical technologies.
Chalcogenide materials belong to a distinctive class of compounds containing elements from the chalcogen group, including sulfur (S), selenium (Se), and tellurium (Te). These elements, when combined, create materials with exceptional optical properties, positioning them as worthy substitutes for traditional germanium optics. Chalcogenide materials have emerged as a germanium substitute primarily because they meet and often exceed the optical characteristics required in the optics industry. These unique glass types not only replace, but in many cases, enhance optical performance in numerous applications. The most notable key performance advantages of chalcogenide are outlined in the next section. Wedge Prism
In designing infrared optical systems, the greatest advantage chalcogenide glasses have over germanium shows up when a designer is looking to athermalize the optical system. The advantage stems from the glass’ lower thermoptic coefficient which is closer to the values other infrared optical materials exhibit, and therefore allow for easier athermalization.
Chalcogenide glasses can be fabricated into optical elements with the same techniques as the germanium, but they have the inherent advantage of being glass which allows many of the compositions to be hot-formed into optical elements. The material distinction allows the use of precision glass molding directly to optical elements with complex aspherical profiles, diffractive surfaces, freeform optics, and lens arrays.
Chalcogenides offer an unprecedented degree of design flexibility and can be meticulously engineered to meet precise optical requirements. This adaptability enables the creation of custom optical components tailored to diverse applications, ensuring optimal optical performance. Because the concentrations of materials used in the melting process when forming chalcogenide glass can be precisely controlled, key optical parameters such as refractive index and dispersion can be engineered at the molecular level making chalcogenide glass extremely customizable. Another feature from the ability to customize the composition of the chalcogenide glasses is the ability to have a significantly extended transmission range when compared to germanium, toward the visible or further into the infrared. This broader range unlocks new possibilities in infrared imaging and spectroscopy by accessing wavelengths previously out of reach with germanium optics.
Chalcogenide optics can be utilized in various applications and use cases where these materials have demonstrated their prowess in enhancing optical performance.
Chalcogenide glass has emerged as a powerhouse in the realm of infrared imaging. Their exceptional properties improve image quality and overall performance, especially in fields where identifying a thermal signature, chemical sensing, and infrared lasers are paramount.
Identifying a thermal signature is critical to the success of surveillance, defense, and search & rescue applications. The identification of a person’s thermal signature (person of interest) vs. a vehicle (active/running vehicle) vs. electronics (hidden but active electronics, and increased resistance in circuits) will increase success rate of the desired application. Many military systems are also seeing size, weight, and performance (SWaP) advantages for drones and head/weapon mounted systems where the weight of optical systems is critical to solider performance and survivability. The thermal signatures of veins in the body, inflamed regions, and body temperature can give medical personnel additional information about their patient(s). They are also used for chemical sensing in the domain of multispectral imaging, hyperspectral imaging, and spectroscopy. The chalcogenide materials shine by offering exceptional optical performance. They provide transmission windows in the shortwave and midwave-infrared regions, allowing for precise and sensitive measurements in chemical analysis and material characterization. This is indispensable in various fields, including gas detection, medical research, agriculture, pharmaceuticals, where high-quality optical performance is non-negotiable.
IR Laser systems, utilizing bulk optics or fiber optics, are an area of interest for those utilizing chalcogenide materials in infrared systems used for range finding, fire control, munitions guidance, and communication which necessitate low-loss materials with minimal dispersion. Chalcogenide optical fibers fit these criteria perfectly, making them the ideal choice for precision infrared laser systems. Their low midwave and longwave-infrared attenuation ensures signals can travel longer distances while maintaining top-notch optical performance.
Chalcogenide materials have swiftly become a strategic choice for the optics industry, offering immediate supply chain benefits by mitigating the impact of germanium export constraints and, more importantly, enhancing optical performance. Optical manufacturers and designers are increasingly turning to Chalcogenides to maintain production continuity, reduce exposure to supply chain disruptions, and meet the exacting demands of customers who demand superior optical performance.
Rochester Precision Optics recently announced it would be scaling production manufacturing of the CLASSIC Series™ of chalcogenide optical materials, the optics industry’s highest-quality alternative substrate to germanium and gallium crystalline materials for use in infrared (IR) imaging optics. As the People’s Republic of China tightens export restrictions on critical materials, RPO is has a domestically developed solution which ensures the security, reliability, and performance leading manufacturers demand.
Recognizing the potential for restrictions by the People’s Republic of China on the export of critical optical imaging substrates and the likelihood of significant market disruption, RPO invested heavily in the manufacturing of chalcogenide glass at its Rochester, NY area facility. CLASSIC-1™ and CLASSIC-6™ moldable chalcogenide glass provides germanium-free material solutions with U.S. Country of Origin. CLASSIC-2™ through CLASSIC-5™ offer moldable glass types with significantly reduced germanium content, critical for the future cost environment wrought by export controls from China. RPO also designs and manufactures custom IR glass material formulations in prototype and production-rate quantities to meet unique program requirements.
One of the most critical advantages of CLASSIC Series glass is the ability to reduce dependence on scarce resources constrained by China, mitigating the risks associated with a volatile global supply chain. By utilizing CLASSIC glass, manufacturers can shift away from adversarial supply sources and embrace domestic manufacturing capabilities, aligning with the vision of a stable and reliable supply chain enabled by U.S. glass production under a U.S.-owned entity.
In conclusion, Chalcogenide materials have emerged as a disruptive force in the optics industry, significantly enhancing optical performance in response to germanium export constraints. Their exceptional optical properties, adaptability, and precision engineering capabilities position them as invaluable assets for achieving top-notch optical performance in a wide array of applications. As the optics industry navigates these challenges, Chalcogenide materials offer a brighter, more robust future, ensuring its continued growth and relevance by setting new standards for optical performance. As the optics industry continues to evolve, Chalcogenide glasses offer viable solutions for maintaining high-performance standards in optical systems while minimizing supply chain risks associated with geopolitical uncertainties.
This article was written by Peter Wachtel, Senior Research Scientist, Rochester Precision Optics. For more information, please visit here .
This article first appeared in the November, 2023 issue of Photonics & Imaging Technology Magazine.
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