IR filters of Pleiger Laser Optics are made of silicon, germanium, sapphire, IR fused silica and ZnSe. The bandpass filters are usually used for gas analysis (H2O, ethanol, methanol, formaldehyde, CO2, CO, NO) and measurement technology.
Neutral density filters (grey filters) are placed in front of the sensors to reduce the amount of light on the detector. Long and short-pass filters are used to block out spectral ranges.