A notch filter selectively removes only specific wavelengths while allowing all other wavelengths to pass through. Unlike typical filters limited to a certain spectral region, the blocked wavelength band can be freely set—from a single wavelength to multiple wavelengths— across ultraviolet (UV), visible (VIS), and infrared (IR) regions. Through advanced multilayer dielectric film design, the filter achieves steep edge slopes and high precision rejection at the designated wavelengths. Notch filters, also known as band-stop filters, exhibit the opposite spectral characteristics of band-pass filters, which transmit only specific wavelengths.
Technical Characteristics
| Parameter | Description |
|---|---|
| Function | Blocks one or more specific wavelengths (single or multiple notches) |
| Spectral Range | Applicable to UV, visible, and IR regions |
| Film Structure | Multilayer dielectric coatings (interference-based design) |
| Edge Profile | Sharp slopes with high wavelength selectivity |
| Blocking Depth | OD4–OD6 or higher (depending on design) |
| Transmission | High transmission outside the blocked wavelength region |
| Design Flexibility | Customizable center wavelength and bandwidth |
Applications
Notch filters are widely used in optical and analytical systems that require precise wavelength suppression:
- Laser systems — rejection of specific laser lines (e.g., 532 nm, 633 nm)
- Raman spectroscopy — removal of laser excitation wavelength while preserving Raman signals
- Medical / Biomedical instruments — fluorescence suppression, imaging enhancement
- Industrial and scientific analysis — wavelength control for optical sensing or diagnostics
Example Specifications
| Type | Description | Blocking Performance |
|---|---|---|
| 532 nm Deep Blocking Notch Filter | Designed to block a single laser wavelength at 532 nm | OD ≥ 6 at 532 nm |
