I hope this isn't too basic for you..

Is there a filter or form of polarization that does it a more specific way, and instead of blocking a particular component of light among many,to instead block all of the compoments that are wrong and only allow a specific component of light through without actually diminishing the beam that you want? In photography terms, no stopping down the light as it passes through, if it gets through, it gets through clean and at the same stop and everything else is stripped? If it can't be quite that efficient, then don't worry about the 1/2, 1/4, 1/8 losses, or whatever values they show up as.. Can you at least get a light that is purely one component?

Is there such a thing as a beam that in an otherwise light free environment can sustain only that component of light and not spread out or difusse to the other unwanted light components again?

Or am I describing something that almost sounds like a L.A.S.E.R.? (even though that is not really my intention)