A polarization beam combiner/splitter is an optical device that combines or splits beams of light based on their polarization. This type of device has several advantages over other beam combining and splitting methods, making it useful for a variety of applications.

How Polarization Beam Combiners/Splitters Work

Polarization beam combiners/splitters depend on the polarization properties of light. Light can be polarized in different orientations, such as horizontal, vertical, or diagonal.

Polarization Beam Splitter:

A polarization beam splitter uses a birefringent crystal to divide a coming beam into two parts that are orthogonal in polarization. For example, it could split a beam into a horizontally polarized component and a vertically polarized component by bending the beam at different angles depending on the polarization.

Polarization Beam Combiner:

A polarization beam combiner does the opposite. It combines two orthogonally polarized beams into a single output beam. The differently polarized beams are bent by the birefringent crystal so that they are parallel in the output.

Advantages over Other Beam Manipulation Techniques

Compared to other methods of combining or splitting beams, polarization beam combiners/splitters have some significant advantages:

Lossless and efficient: The polarization splitting process is lossless, meaning none of the light is absorbed or displaced as heat. This makes polarization beam combiners/splitters extremely efficient. Other techniques, like beamsplitting cubes, lose 50% of the light.

Preserves spatial properties: The polarization manipulation preserves the spatial properties of the beams. The output beams have the same profile and divergence as the input beams. Other techniques can alter beam characteristics.

Wide wavelength range: Polarization beam combiners/splitters work over a wide range of wavelengths, from visible light through near-infrared. Other devices are restricted to smaller wavelength ranges.

Scalable: Multiple polarization beam combiner/splitter stages can be stacked to combine/split many beams. Scaling other devices gets increasingly complex.

Applications Taking Advantage of Polarization Beam Combiner/Splitter Properties

The unique properties of polarization beam combiners/splitters make them ideal for many uses:

Fiber lasers: Polarization beam combiners are used to combine the output from multiple fiber laser amplifiers into a single high-power beam with maintained beam quality.

Laser scanning: Polarization beam splitters can split a beam into components for scanning in different axes. The orthogonal polarizations prevent interference between axes.

Quantum optics: Splitting beams while preserving polarization and spatial properties is critical for quantum experiments dependent on photon entanglement and interference.

Sensors: Polarization splitters can divide an incoming beam into parts to measure different polarization properties for sensing applications.

Laser displays: Beam combiners allow using laser sources with different colors and polarizations to generate a full-color display.

Advanced communication: Spatial division multiplexing with orthogonal polarizations can dramatically increase fiber optic transmission capacity.

Other applications: Polarization manipulators are also used in interferometry, ellipsometry, polarimetry, and many other areas.

By using the fundamental properties of light polarization, polarization beam combiners/splitters provide unique capabilities not possible with other beam controlling optical components. Their lossless, efficient performance and the ability to preserve the spatial properties of combined or split beams make them important for many modern applications in optics, quantum photonics, sensing, and telecommunications. As advanced optical technologies continue to develop, the value of polarization beam combiners/splitters will only increase due to their versatility and performance advantages.