Collection: Laser Line Bandpass Filter

Even though lasers have a very narrow linewidth (a sharp main peak), they are not perfectly clean and suffer from spectral impurities. A bandpass filter is essential for cleanup because it eliminates low-level background noise, primarily Amplified Spontaneous Emission (ASE), and unwanted secondary peaks (side modes).

By having a very narrow bandpass filter centered on the main laser line and high optical density (deep blocking) for all other wavelengths, the filter effectively purifies the beam, drastically increasing the Signal-to-Noise Ratio (SNR) for sensitive applications like spectroscopy.