Skip to content 
4700nm (4.7μm) Infrared longpass Filter
4700nm Infrared longpass Filter is designed to block wavelength shorter than 4700nm and transmit the longer infared wavelength. Coligh manufactures up to 30μm optical filter.
- 50% Transmission Wavelength at 4700 nm
- >90% High Transmission
- Broadband Blocking and Transmission
- Insensitive to Angle of Incidence
- Hard First-Surface Dielectric Coating
Products Categories
Get A Free Quote
4700nm Mid-infrared Longpass Optical Filter Description
The Mid-Infrared Longpass Optical Filter produced by Coligh is a high-performance filter based on optical thin film interference hard film.
- Its main function is to transmit mid-infrared light ≥4700nm. At the same time, it cuts off stray light <4700nmde
- The cut-off wavelength of this filter is 4700nm, forming high transmittance within 5000-10000nm, with a transmittance greater than or equal to 90%, which can maximize the retention of infrared signals.
- The cut-off area is 1500nm-4500nm, and the transmittance at this wavelength is less than or equal to 1%, that is, the cut-off depth OD>=2, which can effectively suppress short-wave interference.
4700nm (4.7μm) Infrared longpass Filter Technical Datasheet
| Parameter | Specification |
| Cut‑on Wavelength (50% T) | 4700nm |
| High‑Transmission Band | ≥ 90% @ 5000nm-10000nm |
| Blocking Region | 1500nm-4500nm |
| Optical Density (OD) | OD ≥ 2 (T < 1%) |
| Substrate Materials | White glass, Sapphire, Silicon, Fused Silica, Zinc Selenide |
| Coating Type | Hard first‑surface all‑dielectric |
| Surface Quality | 80-50, 60‑40, 40-20 scratch‑dig (MIL‑PRF‑13830B) |
| Clear Aperture | ≥ 90% of full aperture |
| Available Diameters | Ø12.7 mm, Ø25.4 mm, Ø50mm, Ø100 mm or custom |
| Thickness | 0.5mm, 1.0mm or custom |
4700nm (4.7μm) Infrared longpass Filter Applications
- Gas detection
The absorption peak of ozone is at 4.7μm, and the absorption peak of nitric oxide is at 5.3μm. These two gases are key indicators for air pollution monitoring. However, because their characteristic absorption peaks are located in the mid-infrared band, they are easily affected by short-wave solar radiation, LED light sources and water vapor, resulting in distortion of detection signals. This filter strictly blocks wavelengths shorter than 4700nm and only projects wavelengths of 5000-10000nm, ensuring that the NDIR sensor captures sufficient characteristic spectral signals of ozone and nitric oxide. - Medical breath analysis
Acetone in human exhaled gas (absorption peak at 4.8um) is a biomarker for diabetes screening, but the strong absorption peaks of water vapor and methane in the breath gas will mask the target signal, and non-related bands need to be accurately filtered out. The 4700nm long-pass filter can cut off short-wave light <4.7μm, that is, the absorption peaks of water vapor and methane, and only transmit the characteristic peak of acetone from 4.8μm to 5.0μm. Improve the accuracy of diabetes screening - Fiber laser processing
In the collaborative processing of fiber laser and CO₂ laser, the reflected light of the short-wave laser will interfere with the infrared thermal imaging system and even damage the InSb detector. . The 4700nm infrared long-pass filter can strictly block the reflected light of the fiber laser <4.7μm, while transmitting the main wavelength of the CO₂ laser for processing monitoring. Reduce the frequency of detector replacement
