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Date : 2006/09/22, Hit : 2975
제목    Periodically Poled Bulk Device & Periodically Poled Waveguide
작성자   Yoon

" Technology ( PPLN, PP-MgO:LN, PP-MgO:SLT ) "

Based on the quasi-phase-matching techniques, QPM, the nonlinear materials' structures are periodically inverted by electric field poling methods to form a well-defined domain patterns bulk device. The QPM technique basically allows two waves to compensate their phase velocity difference within a body of nonlinear crystal. The two phase velocity difference is compensated by shifting the phase relative to one another over a coherent distance through inverting the sign of the nonlinear coefficient, such that it allows an access to all elements of a crystal's nonlinear tensor within its entire transparency range. The periodically poled of bulk non-linear materials are suitable for diverse applications such as optical frequency converter to generate the full spectrum of light source from visible to mid-IR, as high speed switching device for light modulation and as other innovative applications that are yet to be contemplated. As differ to the birefringent phase matching, the QPM technique utilizes the whole transparency range (0.35 um ~ 5.0 um in case of lithium niobate) of the non-linear materials and their highest non-linear coefficient for efficient optical frequency conversion in OPO, SHG, SFG, DFG and OPG laser applications. Other a-periodic pattern designs such as cascaded, fan-out, and customized configuration are also available for applications using the CW, pulsed and ultra-short pulsed laser pumps.

" Non-linear Materials "

Currently, several nonlinear materials are available using the periodically poled technique such as lithium niobate (PPLN), MgO doped lithium niobate (PP:MgO:LN), and MgO doped of stoichiometric lithium Tantalate (PP-MgO:SLT). Both standard and customized QPM grating periods are available based on customers' specifications and requirements for the generation of visible and UV-blue light to near and mid-infrared.

" Technology (PPLN Waveguide, PP-MgO:LN Waveguide) "

Periodically poled waveguides can further enhance nonlinear mixing efficiency as compare to bulk media, by tightly confining optical field over long distances. The tightly focused wave will often diffract when it propagates in a bulk device, so high conversion efficiency cannot be achieved. In waveguides, the mode profile is confined to a transverse dimension on the order of the wavelength, then high optical intensities can be maintained over considerable distance to improve the conversion efficiency by two to three orders of magnitude as compare to bulk devices. Also, the nonlinear mixing efficiency is quadratic ally proportional to the interaction length of the waveguide device, thus the fabrication of long, uniform and low loss waveguide is essential for high efficiency optical frequency mixer.

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