There are many ways to do this. Which option you choose depends on what degree of performance you require, and how much money you re willing to spend.
First of all, you should understand that, while you could apply a wavelength selective coating to a lens, this would much more commonly and cheaply be done with a wavelength filter separate from the lens itself.
Now, the cheapest way to do this would be with a glass filter which absorbs short or long wavelengths selectively. There is a wide range of these available from Schott Glass. I use these commonly, and I've never had trouble. Most vendors will be happy to produce custom shapes, thicknesses, etc.
The down side to filter glass is that it doesn't have a particularly sharp cutoff between the bassband and the stopband. For that, you will need a dielectric coating engineered to your specifications. For that, I would look at CVI or Newport, although there are other vendors out there. There may be something you can use in their catalogs, but custom orders are normal for the optical manufacturing industry, so don't hesitate to call up a sales engineer. In my experience, sales people in this industry are very well educated on their products, or will direct you to an engineer who can tell you exactly what they can produce for you.
Again, there are other vendors you could look at, but these are the ones I would go to first. At the very least, looking at their catalogs will give you an idea of what it is you are really looking for.
