Silicon-based CO2 gas detection mid-infrared narrowband filter at 4260nm wavelength

The 4260nm narrowband filter is an optical component specifically designed for a particular infrared wavelength (4260nm). Its core function is to allow the transmission of light within an extremely narrow band around 4260nm while efficiently blocking light of other wavelengths. Its passband half-width (bandwidth) typically ranges from a few nanometers to several tens of nanometers. This is achieved by depositing multiple layers of optical thin films (such as interference coatings) on a substrate, utilizing the principles of light interference and reflection to enable wavelength-selective transmission.

Technical Characteristics and Classification of 4260nm Narrowband Filters

Core Technical Parameters

• Center Wavelength (CWL): Precisely positioned at 4260nm, this wavelength corresponds to the characteristic absorption wavelength of carbon dioxide (CO₂) gas, making it a critical parameter for gas detection.
• Full Width at Half Maximum (FWHM): As a narrowband filter, its bandwidth is typically less than 2% of the center wavelength. For example, the bandwidth of a 4260nm filter may be controlled within the range of 20-50nm, ensuring high specificity in identifying target gases.
• Transmittance and Blocking Level: It must meet high transmittance requirements in the specific band (e.g., >80%) and provide deep out-of-band blocking (e.g., OD6 level blocking) to minimize background light interference.