Alternative Ways to Understand the Prism Coupler

The Goos-H nchen shift describes the displacement of the center point of an optical beam when it undergoes total reflection from the interface between two semi-infinite regions of different refractive index.

The displacement is generally of the order of the wavelength of light. If the reflection of a beam from a sandwich structure that consists of a semi-infinite prism, a tunneling layer, a waveguide film layer, and a semi-infinite glass slide is investigated, the shift will be found to be much larger as a consequence of the excitation of the guided wave.Terminating the upper (prism) region just beyond the mid-point of the incident beam traps the light of the beam in the waveguide mode in the film.Excitation of the guided wave by an incident beam can also be viewed as a problem in coupled modes, the modes being the waveguide mode and a representation for the incident beam. Power introduced into one branch of a coupled mode structure can transfer to the other branch along the structure.

November 7, 2011

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