Photonics 101- Understanding Beam Splitters

As the name suggests, a beam splitter refers to an optical device which is used to split or divide a beam of light into two. A beam splitter is usually the cornerstone of most interferometers. Beam splitters are available in various forms. These include cubes, pipes and plates. The most common of these configurations is the cube. When in the form of a cube, a beam splitter is made of two triangular prisms that are made of glass. These prisms have their hypotenuses glued together using adhesives which are made of epoxy or UV curable adhesive.  Prior to gluing one of the prism hypotenuse is coated with a dichroic beamsplitting coating. This coating layer of a beam splitter is made in such a way that a percentage of the light entering the beam splitter through one side is reflected while another percentage is transmitted. The sum of the two percentages approximates 100%b and the splitting ratio is controlled by the design of the coating layer on the hypotenuse. Of course the percentages refer to the measure of the beam of light at the design wavelength.

 What happens with a beam splitter is that it accepts the input beam and then proceeds to divide the light depending on the specified requirements. The input beam could be polarized or non-polarized light. Usually, a non-polarizing beam splitter will split the beam on a 50/50 ratio while a polarizing beam splitter tends to lean towards a 95/5 ratio.

Other than the cube beam splitter, there is also the plate beamsplitter which is typically used to produce lower cost non-polarized beamsplitters.  These typically provide a 50-50% split ratio.

A variation of the cube beamsplitter is the pipe beamsplitter which is formed from two rhomboid prisms of different lengths.  The pipe beam splitter is sometimes referred to as a beam displacer. This is because when using the pipe beam splitter it is possible to displace the output beams from each other by the length of the longer rhomboid prism. It is important to keep in mind that a beam splitter, regardless of the form be it cube or pipe, can be made to specifically suit the needs of the customer. This means that they can be made to suit specific wavelengths or for a wavelength band. All you need to do is find someone who is great at combining what you want with the current technology available in the world of photonics.

Tower Optical Corp. is without a doubt the leading innovator as far as making beam splitter is concerned. Not only do we have readily available designs that have impressed our customers over the years, we also do custom designs. Take a look at our site and if you don’t find what you are looking for, get in touch with us. We are more than happy to create a design that meets your needs up to the last one. Our prices are very pocket friendly too.