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This allows quasi-phase-matching to exist at different domain widths . From this equation it is apparent, however, that as the quasi-phase match order increases, the efficiency decreases by . For example, for 3rd order quasi-phase matching only a third of the crystal is effectively used for the generation of signal frequency, as a consequence ...
The structure is designed to achieve quasi-phase-matching (QPM) in the material. Periodically poled crystals are frequently used as nonlinear optical materials. They are more efficient at second-harmonic generation than crystals of the same material without periodic structure.
This would lead to beam walk-off, which limits the nonlinear optical conversion efficiency. Two other methods of phase matching avoid beam walk-off by forcing all frequencies to propagate at a 90° with respect to the optical axis of the crystal. These methods are called temperature tuning and quasi-phase-matching.
Nonlinear photonic crystals are usually used as quasi-phase-matching materials. They can be one-dimensional, [1] two-dimensional [2] or three-dimensional. [3]
Diagram of second-harmonic generation with perfect phase matching =. Diagram of second-harmonic generation with an imperfect phase matching . In this case energy flows forth and back from the pump to the frequency doubled signal, and having a thick crystal can lead to a smaller amount of SHG produced.
This makes it possible to artificially create an electric-field grating with arbitrary period, [7] which satisfies the condition necessary for quasi-phase-matching. Periodic poling is used for efficient frequency-doubling in optical fibers. [8]
Quantitative phase contrast microscopy, a group of microscopy methods; Quasi-phase-matching, a technique in nonlinear optics; Queen's Police Medal, awarded to UK/Commonwealth police officers; Questions of Procedure for Ministers, the confidential predecessor of the Ministerial Code (United Kingdom)
Schematic of SPDC process. Note that conservation laws are with respect to energy and momentum inside the crystal.. Spontaneous parametric down-conversion (also known as SPDC, parametric fluorescence or parametric scattering) is a nonlinear instant optical process that converts one photon of higher energy (namely, a pump photon) into a pair of photons (namely, a signal photon, and an idler ...