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A cold mirror is a specialized longpass filter, an optical mirror which is designed to reflect shorter wavelengths of light at a 45° angle of incidence while transmitting undesired heat (infrared radiation). At Shanghai Optics we manufacture cold mirrors with high surface quality and superb optical qualities.  Our cold mirrors exhibit high reflectance over the entire visible range and excellent transmission in the infrared. Manufactured using special proprietary techniques and coated with a multi layer dielectric coatings, they are the most durable commercially available cold mirrors available today.

Our cold mirrors meet military standard Mil. C-675 and pass snap tape tests. They can withstand high thermal loads, and are capable of operation at temperatures as high as 600 degrees C. They will also operate and perform well in extreme humidity and abrasive environments.

Applications of Cold Mirrors

Cold mirrors are used for a wide range of applications that involve separating light by wavelength. Since the thin film coating on these mirrors transmits infrared away from the application while reflecting visible light at a designated angle, it is a highly effective beam splitter that can be used to remove problematic radiation from a system.

One common application of cold mirrors is in fiber optics. Since optical fiber is damaged by UV and infrared light, a combination of cold and hot mirrors is often used to isolate visible light from UV and IR bandwidths. The mirrors are set up so that only the visible wavelengths are transmitted to the optical fiber, and UV and IR wavelengths are reflected away from the fiber.

Another application of cold mirrors is in lighting applications where IR heat is undesired. The mirror is set up to reflect visible light toward the object to be lit, while infrared radiation is transmitted away (often at a 45 degree angle).

Cold Mirrors from Shanghai Optics

Shanghai Optics is a custom optics manufacturer with over 55 years of optics manufacturing experience, and we take pride in each optical piece that leaves our factory. Our state of the art metrology equipment and careful quality control ensures that each mirror has extremely high visible reflectance and excellent infrared transmission. Our durable dielectric coatings can survive extreme heat and high humidity.  Our mirrors are manufactured from float glass, and our factory standard surface quality is 80-50 scratch dig.  The thickness of each piece is specified to within +/- 0.3 mm, and all other dimensions are guaranteed to be within 0.5mm of stated measures.

Cold Mirrors with a 3.3 nm thickness are available in stock.  We carry one inch and two inch diameter rounds. We also have in stock one inch, two inch and four inch square configurations. Larger sheets are also available and may be cut into custom sizes.

The multi-layer dichroic coating on our cold mirrors reflects an average of greater 95% of light over the wavelength range 420-700nm, and greater than 20 percent over 800-2500nm.

Factory Standard

  • High visible reflectance
  • Excellent infrared transmission
  • Durable coatings will survive extreme heat and high humidity

Please contact us for manufacturing limit or custom specifications.


Dimensions: +0.5mm Material: Float glass
Thickness: +0.3mm Max temperature: 600
Surface flatness: 3per inch Surface Quality: 80-50
AOI: 45°+/-5°
Coating: R>95% avg 420-700nm
R>20% avg 800-2500nm


Cold Mirrors

Part Number Mirror Shape Dimensions
“Diameter, D or Side, axb”
(Inches) (nm) (nm)
Round 1 25.4 3.3
Round 2 50.8 3.3
Square 1.00 x 1.00 25.4 x 25.4 3.3
Square 2.00 x 2.00 50.8 x 50.8 3.3

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