Planar waveguides are waveguides with a planar geometry, which guide light only in one dimension. They are often fabricated in the form of a thin transparent film with increased refractive index on some substrate, or possibly embedded between two substrate layers. For example, a thin neodymium-doped YAG layer can be embedded in undoped YAG with slightly lower refractive index (see Figure 1).
Such active planar waveguides are sometimes used e.g. for optical amplifiers with high gain (compared with that of bulk amplifiers) and relatively high power (at least multiple watts). There are also planar waveguide lasers. Some of these devices can be pumped with a proximity-coupled laser diode, not requiring any pump optics.
|||A. W. Snyder and J. D. Love, Optical Waveguide Theory, Chapman and Hall, London (1983)|
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