Friday is here, and the "A Taste of Science for the Weekend" column is back — number 73.
This week: the connection between germanium, your phone, and missiles — and for the first time in the column, a special guest all the way from New York 😊.
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Sam Rubin is the CEO of LightPath, an American company traded on Nasdaq (LPTH) with a market cap of over $300 million. The company manufactures advanced optical equipment for major clients, including the U.S. government.
This week he is the column's guest of honor, and the piece is based on the fascinating things I heard from him about germanium and optical systems.
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Germanium is a shiny, gray-white element.
In the early days of the computing industry it was used to manufacture transistors, until it was replaced by silicon — which has been with us ever since.
Several properties make germanium special and remarkable.
Germanium conducts electrons efficiently without releasing them randomly as heat.
This property allows it to carry electrical currents at exceptionally high frequencies while maintaining maximum efficiency and low heat loss (similar to gallium).
For this reason it is embedded in the wireless communication component of phones, enabling us to enjoy the high frequencies of 4G, 5G, and Wi-Fi 6.
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Another property is transparency to infrared light.
Although germanium is opaque to visible wavelengths, it is transparent to the longer wavelengths of infrared — making it particularly well suited for use as a lens in thermal sensors and cameras.
To this is added another essential property: a high refractive index.
The angle of refraction of light striking germanium is large, which allows thinner lenses to be used to focus infrared waves onto a sensor.
These properties also make it a critical component at the core of optical fibers.
A high refractive index keeps the light beam traveling through the fiber trapped inside it, bouncing up and down between the fiber's walls rather than refracting outward.
Germanium is also found in the seeker heads of guided missiles, in the base layer of solar panels, and in night-vision systems.
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A small amount of germanium is produced in Belgium and Russia; most comes from China.
Germanium is not mined in its natural form but is extracted from zinc ore, and China holds the dominant share of global production and processing capacity.
China's recent ban on the export of rare minerals included germanium, and prompted a shift in thinking in the United States, which is now focused on developing technologies to replace it.
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Beyond supply challenges, germanium-based lenses perform poorly under varying temperature conditions — such as those experienced by an aircraft or a missile.
When the temperature changes, the angle of refraction of light hitting the lens changes and the image reaching the sensor becomes blurred. Solving this problem requires a cumbersome motorized system that continuously corrects lens focus.
The second problem is that above a certain temperature, germanium begins to become opaque even to infrared light and ceases to be usable.
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Chalcogenide glass is a glass based on different base materials than the silica of ordinary glass, which gives it infrared transparency similar to that of germanium.
LightPath has developed a glass called BlackDiamond, based on chalcogenide glass, which serves as a highly effective substitute for germanium in night-vision systems and thermal cameras.
This glass is inexpensive to manufacture, readily available, more heat-resistant, and does not become opaque at high temperatures — making it an emerging leading candidate to replace germanium lenses across a wide range of applications.
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The traditional industry is moving away from germanium — but a recent scientific breakthrough has already flagged it as a promising material for quantum computers.
Shabbat Shalom 😊
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If you enjoyed the column, you're welcome to follow along and enjoy it again next week.
Video: the ElementGB143 channel on YouTube.
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