Optical Filtration

Wavelength Selection Filters:  have a wide range of spectral applications with regards to "cleaning up" a signal or eliminating "noise" from undesirable periphery wavelengths.  They are also known as Transmission Band Pass, Minus, and Notch Filters

Intensity Beam Splitters can be desired for something as simple as reducing intensity to creating a complex device for optical alignment or interferometry.  They are also known as Beam Splitters, Average, or Polarizing for both Plate and Cube applications

Hybrids Beam Splitters:  have had applications dating back to the dawn of Astronaut Aviation. They have been known as Absorbing Filters, Metal Beam Splitters, Non Polarizing BS, Light Trap, and Induced Transmission Filters

Wavelength Beam Splitters: Split the spectrum rather than Intensity.  They are known by many names Edge Filters,  Long Wave Passes, Short Wave Passes, and some are specifically know as Hot And Cold Mirrors