some questions about optics

Originally posted by KazetNagorra
[b]I don't see how you can have a molecule with no vibrational degrees of freedom unless you are talking about single unbounded atoms or unbounded ions?

Exactly! The problem I would see with using an atomic gas for such a purpose is that you would have to deal with fluorescence.[/b]

In that case, it looks like what I am looking for probably either cannot exist or would be just too awkward.

Originally posted by humy
In that case, it looks like what I am looking for probably either cannot exist or would be just too awkward.

Well, there certainly are optical filters that filter just some narrow bandwidth in the optical range. But just a single wavelength? I don't think so (although it should be noted that because of Doppler broadening, a "single wavelength" will also have a finite bandwidth).

Originally posted by humy
In that case, it looks like what I am looking for probably cannot exist.

I think the OP requirements cannot be met. However I think the requirements you gave later on would be easier to meet. To some degree it sounds like the greenhouse effect except that that is not in the visible spectrum. I believe glass also blocks some UV light quite effectively. So I don't see why you cant find something equivalent that blocks a bit further into the visible spectrum.

Here's an idea: Make a large lcd pane of glass. Then time it to block or let through light in time with a flashing light on your side of the glass. This is similar to the way active 3D glasses work but at a larger scale and with the light source on your side of the glass.

I have seen in a movie, an office with a glass wall that could be turned black at the flick of a switch. Not sure how fast it is, or what technology is used.

edit: Here we are:
http://en.wikipedia.org/wiki/Smart_glass

Originally posted by twhitehead
Here's an idea: Make a large lcd pane of glass. Then time it to block or let through light in time with a flashing light on your side of the glass. This is similar to the way active 3D glasses work but at a larger scale and with the light source on your side of the glass.

I have seen in a movie, an office with a glass wall that could be turned black at ...[text shortened]... is, or what technology is used.

edit: Here we are:
http://en.wikipedia.org/wiki/Smart_glass

If you could pulse the light in the room to make, say, 100 flashes a second (so, to the human eye, the light seems continuous ) with each flash lasting only, say 100ns and with no light emitted between flashes, and if you had windows made of switchable glass that is made to go completely black and absorb all light for just 100ns at a time 100 times a second but be transparent to light for the rest of the time, and if that switchable glass was made to work in phase with the room's light, then that would produce the effect I want because that would stop all light made by the light source in the room going outside while letting through 99% of the light from outside through the glass and into the room.

But I would imagine the biggest challenge with this scheme would probably be making switchable glass that can switch between the two states in just a few nanoseconds and with one state being black and absorbing virtually all light while the other being virtually totally transparent. I would think that would be extremely difficult to design but I am guessing here probably not impossible? -who knows.

Originally posted by humy
If you could pulse the light in the room to make, say, 100 flashes a second .

Active 3D glasses typically work at 60 frames per second. The monitor changes picture 120 frames per second and each eye is on for each second frame of the monitor.
If I set my monitor old CRT at 50hz or 60hz, I notice the flashing, where as most people don't. 100hz looks perfectly steady to me.
A typical fluorescent bulb flashes at 60 flashes per second (assuming your AC current is at 60hz. as it is in Africa). I suspect that florescent has significant afterglow, so maybe LED light would be better.
With the equivalent of active 3D glasses you should then get 50% of the light coming in. I believe making the light source flash shorter pulses would be trivial, but making a window size LCD flash fast might be a challenge. But if monitors can do it, I don't see why it would be impossible. A monitor has lots of small cells and the wiring and cell borders block some of the light, but if your cells are bigger, this might be less of a problem.

http://www.liquidcrystaltechnologies.com/products/LCDShutters.htm

We have developed a novel LCD device that does not have polarizers. Unlike a normal shutter that has polarizers, it has >95% transmission in its clear state.

...toggle rates, up to about 1000 Hz,....

We have made shutters as small as 3mm x 3mm and as large as 355 mm x 406 mm, and usually build them custom to a drawing provided by our customers.

If you are OK with making your window in screen size blocks.

Certainly looks worth investigating.