The challenges of growing the world’s largest sapphire slab

Can optical quality sapphire be grown in a different way to create a large, thick window to protect equipment on the belly of an aircraft?

This is the question that members of the Rubicon Technology design team were asked when the United States Air Force Research Lab (AFRL) called upon them about three years ago to develop a new growth platform that could produce very large polished sapphire infrared (IR) windows.

In the past, these dimensions were met by piecing together several smaller sapphire windows, with less-than-desired performance.

Despite high interest from the defense and aerospace industries, no method for producing sapphire for optical-grade windows of such great size and thickness existed at the time. Sapphire had been limited to smaller sizes and shapes using traditional growth methods. Rubicon studied the problem and agreed that it could be done. In 2012, the Air Force Research Laboratory granted Rubicon a three-year research contract to develop this product.

With several “firsts” already under its belt, such as having been the first to commercialize 6-inch and 8-inch wafers for the LED industry and the first to produce large-diameter patterned sapphire substrates, Rubicon has now successfully become the first to grow a 36 x 18 x 2-inch sapphire slab.

Drawing upon its strong history of scaling up sapphire growth processes, Rubicon successfully produced large sapphire blanks by highly modifying the Horizontal Directional Solidification (HDS) process and developing LANCE. Unlike the ES2 method, which produces high-quality sapphire crystals in the shape of roughly cylindrical boules, the HDS method produces sapphire plates that are advantageous for shaping into large windows.

Scaling up to larger crystal sizes while maintaining crystal quality was, of course, the real test and involved development of a new type of furnace.

Devising how to maintain crystal quality at such a large size proved to be experimental and time-intensive for the designers. By combining multiple platforms, materials and heater types, Rubicon ultimately demonstrated the ability to pull a horizontal boat through a heater surrounded by thermal insulation to achieve the desired thick slab while maintaining its high quality.

Over the past two years, the design team has continued to tweak and perfect the LANCE process, keeping the ultimate goal in mind of producing a sapphire slab with the cut measurements of 36 x 18 x 2 inches. The project is on track to produce optical quality sapphire at this immense size.

Looking to the future, this monolithic sheet is a hugely innovative advance that will provide a large, seamless optical field for military sensing applications and beyond.

For more information on the LANCE project, visit

Case Number 88ABW-2015-1571

Sapphire Industry Watch – February 13

  • Rubicon Technology produces large-area sapphire windows – Aerospace Manufacturing and Design: Rubicon Technology has successfully produced the first synthetic sapphire crystal of its size and thickness, meeting a key milestone in its Large-Area Net-Shape Crystal Extraction (LANCE) project. At 36″ x 18″ x 2″, this piece of sapphire will serve the demanding needs of defense applications, along with future commercial and industrial applications.
  • Madrid’s LED bulbs are street lights ahead of the world (VIDEO) – Malay Mail Online: In an effort to reduce energy consumption, Madrid plans to replace 225,000 traditional street light bulbs with LEDs. The switch is expected to save the city 36 percent of annual energy consumption and reduce CO2 emissions by the equivalent of that generated by 100,000 vehicles in one year.
  • Jefferson scientist’s study of SAD took him to space and back – Lack of light is scientifically proven to be one of the most depressing things about winter. Neuroscientist George Brainard has been testing the biological impact of light and its connection with those who suffer from Seasonal Affective Disorder (SAD). His studies have led him to predict that LED lights will soon displace all other forms of lighting because they offer more flexibility in brightness and color, improving overall health and well-being.
  • Making City Streets Smarter, More Efficient – Lighting and software engineers are working on a new breed of LED street lights that contain sensors with the ability to gather traffic data. The traffic data collected could help ease congestion and help drivers avoid busy roads and intersections. These LEDs are building off of existing technologies that have the ability to dim outdoor lights when no one is around.

Rubicon Technology Develops World’s Largest Sapphire Crystal

In August 2012, Rubicon Technology announced a ground-breaking project to produce large-area sapphire windows of optical quality for military sensing applications. Dubbed Large-Area Net-shape Crystal Extraction (LANCE), the project was supported by a contract from the United States Air Force Research Laboratory (AFRL) Electronic & Sensors Branch, Materials & Manufacturing Directorate, totaling $4.7 million over three years.

Fast forward to today.

Rubicon announced it has reached a key project milestone — successfully producing the first-ever synthetic sapphire crystal of its size and thickness, coming in at an incredible 36 x 18 x 2 inches.

Sapphire Slab

Previous sapphire production methods were incapable of supporting the growth of quality sapphire at the size and thickness needed by the AFRL, so Rubicon developed a new growth platform to achieve the production of very large sapphire windows up to 2 inches thick. The process of creating sapphire of this size was incredibly complex and time-intensive, but Rubicon was determined to deliver a product unlike anything the market had ever seen before.

The military and other high-performance Industries desire sapphire at this size due to a variety of its qualities, including:

  • Strength
  • Optical clarity in the visible and infrared spectra
  • Hardness
  • Abrasion resistance
  • Thermal conductivity

Once thoroughly tested, the sapphire slab produced by Rubicon will be evaluated for use as infrared windows in extreme environments, such as space or the deep sea, where both durability and optical clarity are essential.  The potential uses are almost limitless.  Large-format sapphire will serve demanding applications in defense along with future commercial and industrial applications.

While the project is not yet complete, this is an encouraging breakthrough.

For more information on the LANCE project, visit

Case number 88ABW-2015-0182

New Applications for Sapphire: Aerospace & Defense, Part 1 of 3

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Range of sapphire products available from Rubicon Technology including large optical windows and other shapes for aerospace and defense.

Sapphire’s unique properties make it a perfect material for high-performance applications due to its optical transparency, physical strength, resistance to abrasion and corrosion, temperature durability, chemical inertness, and bio-compatibility. As a result, it is perfectly suited for extreme environments where material durability is just as important as optical clarity.

One extreme use case is in the aerospace and defense industry where there’s a need for rugged windows for targeting pods and missile domes, most notably for the US F-35 fighter jet, that may come in contact with harsh conditions from the harsh, gritty desert with extremely high temperatures to high altitudes with extreme low temperatures.

Market research firm Yole Developpement determined that non-substrate applications for sapphire in the defense, semiconductor and other applications represent 25% of the sapphire industry revenue in a new study.  The market represents a solid growth opportunity for sapphire makers.

While there is opportunity, innovation is needed.  Sapphire traditionally has been limited to smaller shapes and sizes using traditional growth methods.  As sensor technology and applications, in defense and aerospace in particular, have evolved, the size requirements for sapphire windows have grown substantially.  One company that is innovating sapphire crystal growth is Rubicon Technology.

In a recent paper, Rubicon’s Dr. Jonathan Levine, Director of Technical Business Development, detailed how Rubicon successfully produced very large sapphire blanks using a highly modified horizontal directional solidification process. This new method, named the Large‐Area Netshape Crystal Extraction (LANCE) system is currently able to produce crystals of several different orientations. The company plans to produce sapphire windows as large as 36 x 18 x 0.8 inches.

For Further Reading Blog, Opportunities for Sapphire: New Applications & Markets Explained, Blog, How Large Can You Go? Sapphire Windows Grow Up and Across,

Rubicon Technology, Synthesis and characterization of large optical-grade sapphire windows produced from a horizontal growth process,