Newsroom
What is A Pbs?
(Polarizing Beam Splitter)
A PBS (Polarizing Beam Splitter) is an optical component designed to divide an incoming light beam into two separate, distinct outputs based strictly on their polarization states. Unlike standard non-polarizing beam splitters that divide light based on a fixed power ratio (such as a 50/30 or 50/50 split), a PBS reacts directly to the orientation of the light's electric field vector.
Its primary purpose is to isolate and separate the mutually perpendicular S-polarization and P-polarization components of a laser beam, making it an essential building block for optical isolation, coherent signal recombination, and polarization routing.
HOW A Polarizing Beam Splitter (PBS) Works
A PBS can be manufactured as a free-space glass cube, a thin-film plate, or an integrated fiber-optic component. The classic free-space cube configuration operates through three main phases:
Composite Wavefront Arrival
A laser beam containing a mix of polarization states enters the face of the PBS cube. The beam travels through the first glass prism until it reaches the diagonal internal interface.
Dielectric Thin-Film Filtering
The diagonal interface is coated with a microscopic stack of specialized birefringent or isotropic dielectric thin-film layers. The thickness and refractive indices of these optical layers are engineered to exploit Brewster's angle properties at the boundary.
Orthogonal Routing
When the light strikes this internal boundary, the film acts as a polarization-selective valve:
- P-polarized light (parallel to the plane of incidence) passes straight through the boundary without reflecting, exiting the opposite face of the cube.
- S-polarized light (perpendicular to the plane of incidence) is highly reflected at a $90^\circ$ angle, exiting through the adjacent side face of the cube.
