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Why can I see light from TEM00 laser in direction of propagation?

  1. Sep 8, 2013 #1
    In my lab I have a TEM00 laser, so there is no electric or magnetic field in the direction of propagation (call it z direction). However, I know that the intensity of the laser is greatest when my eye is along z direction...why? If there is no electric field along this direction, then what is exciting the molecules in my retina??

    I know that the modern explanation is that the laser is actually a stream of photons, but I am trying to model laser light propagation using classical EM, so I am looking for the classical explanation
  2. jcsd
  3. Sep 8, 2013 #2


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    First of all the laser light is not a stream of photons but, if you wish to express it in terms of quantum electrodynamics, a coherent state, i.e., a superposition of photon states with arbitrary photon numbers.

    Second, as the name of the mode says, both the electric and the magnetic field are transverse. But there is a field, and that excites your retina.

    Third, I hope you haven't really looked directly into the laser light! This is no fun for your eyes!
  4. Sep 8, 2013 #3
    The electric field is still doing the exciting, there's no requirement for this field to be in the same direction as the direction of propagation. The forces on charges due to the wave will be in the polarisation direction.

    This is the nature of the plane wave solution to Maxwell's equations
  5. Sep 9, 2013 #4


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    Isn't all light just like this, with the field vectors perpendicular to the direction of propagation? What's different about the TEM00 laser?
  6. Sep 13, 2013 #5

    Claude Bile

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    Because your eyes have an aperture that the light must pass through before it is detected by the retina. Obviously if the aperture is aligned in the direction of the laser, you will detect the most light.

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