- Periodic poling
Periodic poling is formation of layers with alternate orientation in a
birefringent material. The domains are regularly spaced, with period in a multiple of the desiredwavelength of operation. The structure is desired to achievequasi-phase-matching (QPM) in the material.Periodically poled
crystal s are frequently used asnonlinear optical materials. They are up to 20 times more efficient atsecond-harmonic generation than crystals of the same material without periodic structure. The material for the crystals is usually a wideband gap inorganic crystal, or in some cases a suitable organicpolymer . Some popular materials in current use are KTP,lithium niobate , andlithium tantalate .The periodic structure is created in the crystal using a range of techniques. Pulsed electric field, electron bombardment, thermal pulsing, or other methods can be used to reposition the
atom s in thelattice , creating oriented domains. This can be achieved either during the growth of the crystal, or subsequently. [http://www.iop.org/EJ/abstract/0022-3727/28/9/001]External links
* [http://www.rp-photonics.com/periodic_poling.html Encyclopedia of laser physics and technology]
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