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Can we make light slower by applying optical trapping (I mean applying laser beam to lower the speed of light)?

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You've got the wrong idea about optical trapping. Or perhaps you're referring to something I've never heard of? Can you elaborate? – ptomato Feb 23 '13 at 21:39
up vote 2 down vote accepted

There's a number of ways to create what is called slow light. You presumably mean the term as used in the same context as Electromagnetically induced transparency.

Here you shine the light pulse you want to slow on to a cloud of atoms, and simultaneously shine a second beam on them. The resulting interactions then make for a very strong dependence of the cloud's absorption and dispersion on the frequency of the light. This can then slow the group velocity down to a few meters per second.

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There are many ways to confine light. Keywords: optical confinement, confine light

See Photonic crystals: New designs to confine light, Confining light for use in nanophotonic devices.

You can make light slower by making it go through a medium with higher refractive index. For example, water has a higher refractive index than vacuum so light travels slower in water than in vacuum. (Microscopic explanation of refraction)

If you're wondering about what happens when two photons collide, then:

Even with low energy photons, there are virtual loops and photon photon interactions can happen with some probability-anna v

If the energy is large enough, photons interactively create massive particles. -datenwolf

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