From the optical bench
ZnSe blog.
Not a brochure.
Twelve posts on composition, zinc, selenium, CVD growth, grades, SMTY, blanks, AR, Fresnel loss, maximum size, handling, and thermal vs CO2. Written as we quote the crystal — not as a press release.
What ZnSe actually is
An optical engineer’s note on zinc selenide: 1:1 Zn and Se, cubic zincblende, why the crystal is amber, and which numbers actually matter on a quote.
Zinc: the quiet half of ZnSe
Why the cation is zinc, how Zn metal becomes Zn vapor in a CVD reactor, and why zinc purity shows up as 10.6 µm absorption.
Selenium, H2Se, and why this plant smells like a problem
Selenium is the anion in ZnSe. Hydrogen selenide is the process gas. Both are why CVD zinc selenide is a chemical plant, not a glass shop.
How CVD ZnSe is actually grown
Chemical vapor deposition of zinc selenide: zinc vapor, H2Se, a hot mandrel, a polycrystalline plate, then grinding. What we grow in Gwangju and what we do not.
Laser grade vs optical grade ZnSe
Laser-grade ZnSe is specified around 10.6 µm absorption. Optical grade is specified around imaging scatter. Putting the wrong one in a resonator is how you write a failure report.
SMTY: sufficient material to yield
SMTY ZnSe is water-jet nested stock cut about 2 mm fat so your shop yields the blank without buying a whole mother sheet.
Windows, cores, and edged blanks
Finished ZnSe windows vs core-drilled blanks vs edged stock. The +2.032 mm, ±0.254 mm, and chip <0.762 mm numbers we actually run.
AR coating ZnSe at 10.6 µm (and the HeNe problem)
Uncoated ZnSe throws away ~17% per face at 10.6 µm. AR is not optional on a resonator. Dual-band with 633 nm is a design, not a checkbox.
Handling ZnSe: soft, toxic, not a glass blank
Knoop ~110, selenium chemistry, gloves, no dry grind, SDS with the quote, and return-for-disposal of spent windows.
Same crystal, two jobs: thermal imaging vs CO2
ZnSe serves 10.6 µm lasers and 8–12 µm cameras. The grade, the AR, and the competitors (Ge, ZnS, Si) are not interchangeable.
Uncoated ZnSe and Fresnel loss
n = 2.403 at 10.6 µm. About 17% per face uncoated. AR is a line on the RFQ, not a default.
What Ø800 × 30 mm means on a quote
KM datasheet maximum. Photographed plates in the 800 × 1200 / 800 × 1400 mm class. Send the aperture, not a hope.