Polarizing Cube Beamsplitters

Beamsplitters do exactly what their name implies, split a beam at a designated ratio in two directions. Standard beamsplitters are commonly used with unpolarized light sources such as natural or polychromatic, they split the beam by the percentage of intensity, such as 50% transmission and 50% reflection, or 30% transmission and 70% reflection. Dichroic beamsplitters split the incoming light by wavelength and are commonly used in fluorescence applications to separate the excitation and emission paths, these beamsplitters offer a splitting ratio that is dependent on the wavelength of the incident light and are useful for combining / splitting laser beams of different colors.

Beamsplitters are often classified according to their construction: cube or plate. Cube beamsplitters are essentially composed of two right angle prisms cemented together at the hypotenuse with a partially reflective coating in between. The hypotenuse surface of one prism is coated, and the two prisms are cemented together so that they form a cubic shape. To avoid damaging the cement, it is recommended that the light be transmitted into the coated prism, which often features a reference mark on the ground surface.
Advantages of cube beamsplitters include easy mounting, durability of the optical coating since it is between the two surfaces, and no ghost images since the reflections propagate back in the direction of the source. Disadvantages of cube are that it is bulkier & heavier than other types of beamsplitters and doesn’t cover as wide a wavelength range as pellicle or polka dot beamsplitters. Though we do offer many different coating options. Also cube beamsplitters should only be used with collimated beams since converging or diverging beams contribute to considerable image quality degradation.

Paralight Optics offers cube beamsplitters available both polarizing and non-polarizing models. Non-polarizing cube beamsplitters are designed to split incident light by a specified ratio that is independent of the light’s wavelength or polarization state. Whereas polarizing beamsplitters will transmit P polarized light and reflect S polarized light allowing the user to add polarized light into the optical system, they can be used to split unpolarized light at a 50/50 ratio, or for polarization separation applications such as optical isolation.

Features:

Substrate Material:

RoHS Compliant

Optical Performance:

High Extinction Ratio

Reflecting S Polariztion:

By 90°

Design Options:

Custom Design Available

Common Specifications:

pro-related-ico — Reference Drawing for

Polarizing Cube Beamsplitter

Note: The extinction ratio (ER) is defined as the ratio of transmitted p-polarized light to s-polarized light, or Tp/Ts. However, it is important to recognize that Tp/Ts is not usually equal to the ratio of reflected s-polarized light to p-polarized light, or Rs/Rp. As a matter of fact the ratio of Tp/Ts (ER) is almost always better than the ratio of Rs/Rp. This is because beamsplitters are generally effective at reflecting s-polarization but they are not as effective at preventing p-polarization from reflecting, i. e., transmitted light is almost free of s-polarization, but reflected light is not totally free of p-polarization.

Parameters

Ranges & Tolerances

Substrate Materials

N-BK7 / SF glass
Type

Polarizing cube beamsplitter
Dimension Tolerance

+/-0.20 mm
Surface Quality (Scratch-Dig)

60-40
Surface Flatness (Plano Side)

< λ/4 @632.8 nm per 25mm
Transmitted Wavefront Error

< λ/4 @632.8 nm over clear aperture
Beam Deviation

Transmitted: 0° ± 3 arcmin | Reflected: 90° ± 3 arcmin
Extinction Ratio

Single Wavelength: Tp/Ts > 1000:1
Broad Band: Tp/Ts>1000:1 or >100:1
Transmission Efficiency

Single Wavelength: Tp > 95%, Ts < 1%
Broad band: Tp>90% , Ts < 1%
Reflection Efficiency

Single Wavelength: Rs > 99% and Rp < 5%
Broad band: Rs >99% and Rp < 10%
Chamfer

Protected < 0.5mm X 45°
Clear Aperture

> 90%
Coating

Polarizing beamsplitter coating on hypotenuse surface, AR coating on all input and output surfaces
Damage Threshold

>500mJ/cm², 20ns, 20Hz, @1064nm