Slow light with Photonic Crystals
Dear All,
For tomorrow’s Agora session, we will discuss one of the applications of Photonic crystals -controlling ‘Slow light’. I have chosen a paper titled ‘Slow light in Photonic Crystal Waveguides’ by Krauss . The paper gives an interesting overview of the principles behind slowing light down in Photonic crystals and its significance. Please find the link below
http://iopscience.iop.org/0022-3727/40/9/S07/pdf/0022-3727_40_9_S07.pdf
Meet you all in the library tomorrow, at the usual time (12:30!)
Cheers,
Gopika
1 comment
Hi,
This actually refers to the previous paper on use of a photonic bandgap material especially to prevent spontaneous emission (at frequencies within that bandgap). I think I agree with the physical principles in the paper, but found some (or all) of the discussion regarding applications rather far-fetched and basically impractical — I said that at the 2nd meeting (sorry, I was sick last week so I might have missed further discussion). I think I even agree that you could use the metal film resistor to deliver a current with subpoissonian shot noise to an LED which (if it is nearly 100% efficient) would create a stream of photons with subpoissonian noise (aka squeezed state).
I pointed out previously how impractical it would be to use this squeezed state to lower the noise in an optical communications system (it would require transmission with almost no attenuation and detection with near 100% quantum efficiency). I will put practicallity aside.
Now thinking about it further I also believe that you could create a laser diode taking advantage of the same concept (figure 5). However I think there is a flaw in the concept. Even if you could add energy to the internal wave photon by photon, one for each electron (as I’m willing to concede) it would NOT deliver an output laser beam with a similarly reduced noise. That is because the internal wave of the laser is sampled by the semi-transparent output mirror which randomly allows some (rather small) proportion of the power (photons) to escape. That process itself reintroduces the poisson noise level (just as would attenuation in the communications channel, my previous objection). I also believe that temporally coherent laser radiation with subpoissonian noise would violate the uncertainty principle (but having said that, I need to figure out why it might not apply to the internal wave….).
However with the squeezed-state LED (mentioned on the last page), this objection doesn’t apply, since all photons are directed into the output. But I still insist on the total impracticality of the following communications channel!!
– Jeff