What is a Dichromatic Prism and How Does it Work?

[Roodles01]

I found what was called a "dichromatic prism" on ebay and bought it. It is a cube and although described as "not perfect" it splits light extremely well and is quite a cool object to show those in my staff room.
I understand that dichroic is different but not sure how.

Question is, how does it work?
Considering it's made of what looks like a single piece of material how the heck did those almost invisible planes get in there.

Cool it may be, but not understanding it is annoying.
Can anyone help?

 

[goodphy]

As you can see image in internal search. This prism is consisted of two pieces of prism attached to each other. On the interface between two prisms, there is a optical coating which reflects certain range of frequency (it is color perceived by human brain) and transmits other frequency band. This split beam can reflect the prism surface from inside unless they escape from the prism. As a result, you can see the different colors from different angle of the prism.