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1.INTRODUCTIONMaterion Balzers Optics history dates to 1960 with the founding of Balzers. Our LWIR heritage dates to 1972 with the founding of Barr Associates. Both companies have undergone significant growth and transitions since then to become combined as one of the worlds leaders in optical coatings (see fig 1). With over 900 employees and 100 deposition systems worldwide MBO offers a uniquely broad rand of optical coatings (see fig 2). As noted in fig 2, our LWIR strength and capability resides withing our US facility in Westford MA (see fig 3) 2.LWIR MANUFACTURING APPROACH2.1Deposition systemsLWIR coatings are typically defined as those operating withing the 8.0um – 14.0 um range. Coating in this range offers unique challenges as well as an extremely broad (and growing) range of applications. These include (but are not limited to) flame detection, thermal imaging, medical, non-contact temperature measurement, motion sensors, deep space exploration and climate monitoring. Over the past 40 years MBO has custom designed and built multiple e-beam depositions systems. As specifications tightened with regards to uniformity, wavelength positioning, T% and blocking density MBO responded with custom designed equipment. Including the use of plasma systems for enhanced durability. Our LWIR deposition processes employ some of the most advanced thickness control systems, using state of the art optical, crystal and time/power monitoring. Most having been designed and fabricated in-house based upon decades of LWIR manufacturing experience. 2.2Substrate selectionOur preferred LWIR substrate materials are Ge, Si, ZnS, ZnSe. Each having their own benefits and tradeoffs. See fig 4 with some information on different substrate materials. This information is key to making the proper substrate selection. While we do occasionally use other types of substrate material (CdTe for example), those add to the difficulty and complexity of the LWIR coatings therefore are only used in extreme cases when customer specification require this. 2.3Coating MaterialsWhile there are a limited number of options for making environmentally stable, durable, and high performance coatings we do have a few options we routinely use as well as some unique blends. Our standard materials in this wavelength region are Zns, ZnSe, Ge, CeF3, Yf3, Thf4. Table 1 shows some of the properties associated with these. Table 1
Several factors go into deciding what material set is best suited for that particular coating design and application. Some of this is based upon design performance and durability, while some is based upon heritage and previous experience. With regards to Thf4. We do use this material on limited occasions however due to it being a radioactive alpha emitter it’s use has been mostly phased out. MBO currently replaces this material with Yf3 based materials whenever possible. 2.4Custom DesignsAll our LWIR items are custom designs to customer specifications. Using state of the art software combined with years of experience and heritage MBO can design a wide range of LWIR coatings using a variety of materials and design techniques. Fig 5, 6 & 7 displays some custom design examples. 3.DEMONSTRATED RESULTSMeasured performance results of a MBO LWIR coating (12.0 um bandpass) are presented in Figs 8, 9 & 10. Performance demonstrated here is similar to all MBO’s LWIR bandpass filter offerings. 4.COMPLEX CUSTOM SOLUTIONSIn addition to the discrete filters referenced previously in this paper MBO has the proven capability in providing assembled LWIR multispectral filter arrays (see fig 10). This is accomplished by combining our butcher block assembly and LWIR coating processes. With demonstrated ability to use multiple substrate materials (Ge, Si, ZnS, ZnSe & sapphire) our LWIR assembled exhibit the following attributes.
Materion’s LWIR capability extends into wafer level offerings where we have proven capability to coat large form (up to 200mm) wafers with complex LWIR optical coatings. These wafers exhibit ultra-low defect levels (< 0.040mm), precision patterning, deep well coating, getter and metallization. Fig 11 illustrates our comprehensive wafer level capability. 5.VLWIR – FUTURE OFFERING?Recent request to Materion for optical coating beyond 20um (50um - 100um) have initiated internal discussion and evaluation on how best to achieve these performance requirements. To date the challenges have been identified and preliminary investigation has begun to determine the optimal approach for solving each. Some of these challenges are. 6.CONCLUSIONIn this paper, Materion Balzers Optics shows existing LWIR processes and capabilities. Covering a variety of optical coating types (band passes, beam splitters, etc.) used in multiple configurations including discrete filters, multispectral arrays and wafer level coatings. The paper additionally presents our interest and willingness to push our capabilities beyond 20um. ACKNOWLEDGEMENTSMaterion Balzers Optics would like to thank all partners for their support during development and manufacturing of optical components discussed. REFERENCESAustin A. Richards,
“Alien Vision: Exploring the Electromagnetic Spectrum with Imaging Technology,”
SecondSPIE Press Book)Google Scholar
.Coating Materials News,”
https://materion.com/resource-center/newsletters/coating-materials-news Google Scholar
James D. Rancourt,
“Optical Thin Films User’s Handbook,”
McGraw Hill1994). Google Scholar
“Coatings Used in Space,”
Coating Materials News, https://materion.com/resource-center/newsletters/coating-materials-news Google Scholar
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