Your Cold Mirror Questions, Answered (Laser Material Processing)

Every Laser Material Processing system eventually meets the same question: where does the light go, and how much of it survives the turn? A well-specified Cold Mirror…

Every Laser Material Processing system eventually meets the same question: where does the light go, and how much of it survives the turn? A well-specified Cold Mirror answers both, which is why it earns a place on the bill of materials long before the enclosure is drawn.

Think of the Cold Mirror as a precisely made float or borosilicate glass plate whose working surface is a dichroic (reflects visible, transmits IR). The result is > 98% visible reflection across visible reflect / IR pass, which is exactly what most Laser Material Processing builders are looking for.

Reflection on a first surface is straightforward physics: photons strike the coated face and are returned according to the law of reflection, angle in equals angle out. Because the coating sits on top, there is no second surface behind it to create a faint ghost image, which matters whenever contrast or measurement accuracy is at stake.

Most of the engineering in a Cold Mirror lives in its dichroic (reflects visible, transmits IR). The stack is designed for visible reflect / IR pass and delivers > 98% visible, and its environmental protection layer keeps the metal from tarnishing so the mirror keeps working year after year.

Substrate choice for a Cold Mirror is a trade between optical grade and budget. float or borosilicate glass is a common pick because it can be cut and polished to 4–6λ flatness and a 60-40 surface, which is plenty for the reflection quality most Laser Material Processing systems require.

When you specify a Cold Mirror, the numbers that matter are flatness 4–6λ, finish 60-40, and the reflectance > 98% visible across visible reflect / IR pass. Thickness 1–3 mm is mostly about handling and mount compatibility, but it still belongs on the print. The specification table covers the common configurations.

Most Laser Material Processing engineers reach for a Cold Mirror when they need cutting, welding and marking where beam stability decides part quality. The component's job is unglamorous but essential — keep the light on course and the loss low.

Frequently asked questions

Does a Cold Mirror need a specific mount angle? Not inherently, but 0° or 45° are most common; tell your supplier the angle so the coating is optimized. Can it be customized? Yes — size, shape, substrate (float or borosilicate glass) and dichroic (reflects visible, transmits IR) are all adjustable. What reflectivity can I expect? Around > 98% visible across visible reflect / IR pass for standard builds.

A short checklist covers most Laser Material Processing cases: what band (visible reflect / IR pass)? at what angle? how much loss is allowed (> 98% visible)? then pick dichroic (reflects visible, transmits IR) on float or borosilicate glass at 1–3 mm. Getting these four right avoids the most common rework — the application notes show how each sector resolves them.

A Cold Mirror is tougher than it looks but softer than you think. Fingerprints on the dichroic (reflects visible, transmits IR) are the usual cause of field failures, so edge-handling and capped storage pay off. A little discipline keeps > 98% visible where it belongs.

Because we control cutting, coating and finishing in one place, a Cold Mirror can move from your drawing to a finished part without hand-offs. The float or borosilicate glass is cut to ±0.01 mm, the dichroic (reflects visible, transmits IR) is vacuum-deposited for > 98% visible over visible reflect / IR pass, and the result is inspected to 4–6λ flatness and 60-40 quality.

One term worth knowing

"Reflectivity" on a Cold Mirror is the fraction of incident light returned by the dichroic (reflects visible, transmits IR). Quoting > 98% visible without the band (visible reflect / IR pass) is meaningless, because the same coating can be excellent at one wavelength and poor at another — always pair the number with the range.

Mirrors reward careful handling. Hold a Cold Mirror by the edges, keep the coated face away from fingers and aerosols, and clean only with approved optics tissue and solvent when truly needed. Store it in its packaging, coated face protected, and it will hold > 98% visible for years.

A practical Cold Mirror datasheet reads: float or borosilicate glass substrate, 4–6λ flatness, 60-40 quality, 1–3 mm thick, > 98% visible over visible reflect / IR pass. Those five lines settle most design reviews for Laser Material Processing. See the standard size list for what we stock and what we cut to order.

A Cold Mirror starts as a float or borosilicate glass blank. We hold it to 4–6λ flatness and 60-40 surface quality, then apply the dichroic (reflects visible, transmits IR). The substrate never sees the beam directly, but its figure sets the limit on how straight the reflected wavefront stays.

A Cold Mirror is tougher than it looks but softer than you think. Fingerprints on the dichroic (reflects visible, transmits IR) are the usual cause of field failures, so edge-handling and capped storage pay off. A little discipline keeps > 98% visible where it belongs.

Beyond Laser Material Processing, the same Cold Mirror shows up in laboratories, teaching setups and OEM builds where cutting, welding and marking where beam stability decides part quality. Its value is generality: one well-made part serves many breadboards, which is why stocking a few standard sizes pays off.

Every Laser Material Processing system eventually meets the same question: where does the light go, and how much of it survives the turn? A well-specified Cold Mirror answers both, which is why it earns a place on the bill of materials long before the enclosure is drawn.

How the part is checked

Before a Cold Mirror leaves the line it is inspected for flatness (4–6λ), finish (60-40) and reflectance (> 98% visible over visible reflect / IR pass). A simple 45° visual check reveals coating defects, and a flatness test confirms the wavefront stays within tolerance — the same discipline JYOPTO applies across its optical glass, vacuum-coating and precision cold-processing since 2020.

How the part is checked

Before a Cold Mirror leaves the line it is inspected for flatness (4–6λ), finish (60-40) and reflectance (> 98% visible over visible reflect / IR pass). A simple 45° visual check reveals coating defects, and a flatness test confirms the wavefront stays within tolerance — the same discipline JYOPTO applies across its optical glass, vacuum-coating and precision cold-processing since 2020.

The Cold Mirror is not exclusive to Laser Material Processing. Universities, service centers and R&D groups use it wherever a beam must turn, which makes a flexible, customizable part a quiet workhorse across the optics world.

Quality control

Every Cold Mirror is measured, not just sampled. Flatness against a reference, scratch-dig against 60-40, and a reflectance spot-check at visible reflect / IR pass confirm the dichroic (reflects visible, transmits IR) performed as designed. Documented results matter most for Laser Material Processing, where one bad part can stall a whole instrument.

The dichroic (reflects visible, transmits IR) is where performance is won or lost. Deposited by vacuum processes, it is tuned so the reflected wave adds constructively across visible reflect / IR pass, reaching > 98% visible. Getting the layer thickness right is a precision task: a few nanometers off and the reflectivity curve shifts.

Think of the Cold Mirror as a precisely made float or borosilicate glass plate whose working surface is a dichroic (reflects visible, transmits IR). The result is > 98% visible reflection across visible reflect / IR pass, which is exactly what most Laser Material Processing builders are looking for.

Wrapping up

A Cold Mirror is a small part with an outsized effect on Laser Material Processing. Get the dichroic (reflects visible, transmits IR), float or borosilicate glass and flatness right and the rest of the system behaves. If your drawing calls for something specific, the team at JYOPTO can cut and coat it to match — start from the specifications and standard sizes, then tell us the wavelength and angle.