Why not use a box-type beam splitter

Cube beam splitters are not always ideal because they can be heavier, more expensive, and less suitable for high-power or UV applications compared to plate or pellicle alternatives.Limitations of Cube Beam Splitters1. Optical Cement Degradation: Cube beam splitters are made by cementing two prisms together. High-power lasers or prolonged UV exposure can degrade the optical cement, leading to reduced performance or failure over time . 2. Weight and Size: Cubes are bulkier and heavier than plate beam splitters, which can be a disadvantage in compact or portable optical systems . 3. Ghosting and Multiple Reflections: While cubes reduce ghost images compared to plates, they still introduce additional surfaces that can reflect light internally, potentially affecting interferometric measurements if not properly aligned . 4. Cost: Cube beam splitters generally require more material and precise assembly, making them more expensive than plate alternatives . 5. Limited Flexibility in Path Lengths: Cubes maintain equal path lengths for transmitted and reflected beams, which is advantageous in some setups but can be restrictive if a shorter optical path or specific beam geometry is needed .When Plate or Pellicle Splitters Are PreferredHigh-Power or UV Lasers: Plate splitters avoid cement, reducing the risk of damage from high-intensity or UV light .Compact Systems: Plates are lighter and easier to integrate into larger optical assemblies .Cost-Sensitive Applications: Plates are simpler to manufacture and generally cheaper .Minimizing Ghosting: Pellicle splitters, which use a thin membrane, can eliminate ghost reflections entirely, making them ideal for sensitive interferometry .SummaryWhile cube beam splitters offer advantages like consistent splitting ratios and equal path lengths, they are not always the best choice due to cement degradation under high-power or UV light, higher cost, bulkiness, and potential internal reflections. Alternatives like plate or pellicle beam splitters are often preferred in applications requiring lightweight, cost-effective, or high-power-compatible solutions.