nanoHUB U Nanophotonic Modeling/Lecture 1.11: Other 2D Photonic Structures
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[Slide 1] Hi everyone, welcome to Lecture 1.11. So this is considering other 2D photonic structures that we haven't talked about yet. 

[Slide 2] So the first type of 2D photonic structure that's really unique and interesting, may have some practical applications, is this so called micro add/drop filter. Here the premise is the following. Which is that in telecommunications, often times, light is sent around as a combination of different wavelengths in fiber optics. And so then, if you can actually send light down multiple wavelengths at once, then you can convey much more information than at a single wavelength alone. And that's actually known as wavelength division multiplexing. However, in some cases you may have to actually join together multiple wavelengths in one physical location, but then you may have to split them apart at others. Say communicating from some sort of hub, like Facebook's data center, to individual optical fiber network into the home. Like a Verizon FIOS network or so on. Then, you would need the ability to kind of easily add or drop different wavelengths. And so then this is actually showing that if you have a photonic crystal design of two resident modes that have even and odd symmetries. And they're degenerate in their key resonant frequencies. And have the same decay rate. Then they can actually be set up to interact with each other so that they would only transmit or drop a specific targeted frequency. And they would drop nothing else. And so this is actually shown explicitly as kind of this transmission, which you can see is essentially one for almost every frequency. And then it just drops for this very, very narrow range of frequencies. And this can be targeted to whatever frequency you need it to be. And so then this allows you to drop one frequency, but then let everything else pass just like nothing happened. And so that can be very nice capability. 

[Slide 3] Another kind of photonic crystal structure that's very interesting is the so called photonic crystal fiber. And you can use either 1D periodic or 2D periodic structures. And then you can roll them around into a fiber. And so what's nice about the 1D and 2D periodic photonic crystal fibers, is that they can actually guide light in air. And so, there are a couple advantages to guiding light in air. The first being that it reduces the losses or absorption. So if you had say like a very high-powered laser, then you actually don't have to absorb that light, like as you would in a fiber optic. And then it could also be flexible enough that you can use it for surgery or other therapeutic applications. But then second, it's also really good for sensing or detecting in air. So, if there was some sort of toxic chemical in the environment, then you could actually let it flow through the middle of this photonic crystal fiber. And then if you had some sort of chemical that can bind to it, then it could help emit and then detect light down the fiber. And then allow you to very easily and quickly detect any kind of threat before it became dangerous to humans. So, in summary, there are a lot of interesting applications and designs for 2D photonic crystals. And more of it may be yet to come. But in future lectures, I'll actually talk about, what are some even more complex 3D structures that we can build?