Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Time delay for evanescent wave to spread (photon tunnelling)

  1. Aug 26, 2008 #1
    Nimtz and Stahlhofen claim that their recent tunnelling experiment proves that tunnelling time for light between double prisms is zero. In Herbert Winful's response to this (http://arxiv.org/ftp/arxiv/papers/0709/0709.2736.pdf) he explains that the evanescent wave formed in the gap only has real propagation along the surface of the prism (not towards the second prism). He compares the gap to a cavity that holds energy, transverses the distance of the Goos-Hanchen shift, and then releases the energy simultaneously out of both sides of the gap. I have two questions..

    1) It makes sense that after the evanescent wave fills the gap it is able to "leak" out energy into both prisms, but does it not take time for the evanescent wave to fill the gap? Why does this time not vary with gap length?

    2) I have also read that this evanescent wave is a standing wave that oscillates, but it is not clear to me in which direction it oscillates? Does the waves move downwards due to the goos-hanchen shift and then another evanescent wave from new incident waves begins at the incident point periodically resulting in a standing evanescent wave moving up and down the goos-hanchen shift with time?

    sorry for my ignorance this is all very new to me and I'm just trying to grasp what I can..
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted