Beam splitters are divided into stages based on how they split light: by intensity, polarization, or wavelength, and by their physical construction such as cube, plate, or specialized designs.

Classification by Optical Function

Beam splitters can be categorized into different stages according to the optical property they manipulate:

• Non-polarizing beam splitters: Split light based on intensity, maintaining the original polarization state. The splitting ratio (e.g., 50/50) defines how much light is reflected versus transmitted .
• Polarizing beam splitters: Separate light into orthogonal polarization states, reflecting S-polarized light and transmitting P-polarized light. These are essential in laser systems and polarization-sensitive measurements .
• Dichroic or wavelength-selective beam splitters: Split light based on wavelength. Shortpass splitters transmit light below a cutoff wavelength and reflect longer wavelengths, while longpass splitters do the opposite. Multi-band splitters handle three or more wavelength bands .

Classification by Physical Construction

Beam splitters are also divided by their structural design, which affects their optical performance:

• Cube beam splitters: Constructed from two triangular prisms glued together at their hypotenuse with a semi-reflective coating. This design maintains beam alignment and is compact, making it suitable for interferometry and precision optics .
• Plate beam splitters: Thin, flat glass plates with a partially reflective coating on one surface. They are simpler, lighter, and cost-effective but can introduce beam displacement and are often used at a 45° angle of incidence .
• Specialized designs: Include pellicle beam splitters, crystal-based splitters, Brewster windows, and wedged plates, each optimized for specific applications such as minimizing chromatic aberration or handling high-intensity lasers .

Operational Stages

In practical applications, beam splitters operate in stages depending on the system requirements:

1. Initial splitting stage: The incoming beam is divided according to the chosen property (intensity, polarization, or wavelength).
2. Intermediate manipulation stage: Split beams may pass through additional optical elements like mirrors, lenses, or filters to direct or condition the light.
3. Final recombination or detection stage: In interferometers or imaging systems, the split beams may be recombined or directed to detectors for measurement, analysis, or display .

Summary

Beam splitters are divided into stages both functionally (intensity, polarization, wavelength) and structurally (cube, plate, specialized designs). Understanding these stages is crucial for selecting the appropriate splitter for applications in interferometry, laser systems, optical instrumentation, and imaging technologies .