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Abstract
周期分極反転LiNbO_3結晶中の光学フォノンに着目したコヒーレント反ストークスラマン分光(CARS)とその応用について述べる.Z軸方向の偏光を用いたA_1ポラリトンモードのCARSにより,分極反転周期に依存する新たな共鳴ピークをテラヘルツ帯に見出し,これが差周波テラヘルツ波発生とアップコンバージョン(光波帯での検出)を含む擬似位相整合カスケードプロセスに起因していることを明らかにした.また,分極反転領域と非反転領域においてEモードCARSスペクトルに相違が現れることを見出した.これを用いたCARSイメージングにより,非破壊に周期分極反転構造を可視化することに成功した.
Coherent anti-Stokes Raman spectroscopy (CARS) of optical phonons in periodically poled lithium niobate (PPLN) crystals and its application are demonstrated. Using CARS of PPLN crystals with the laser sources polarized along the Z axis, exciting the A_1-polariton modes, we found a novel period-dependent resonance in the terahertz-frequency region. This resonance originates from the quasi-phase-matched cascade process including the difference-frequency terahertz-wave generation and its upconversion (optical detection). Furthermore, we also found spectral changes in the E mode, dependent on the distribution of ferroelectric polarizations. This effect successfully provides a novel method for non-destructive imaging of periodically poled domain structures by CARS.
Journal
- Technical report of IEICE. LQE [List of Volumes]
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Technical report of IEICE. LQE 108(194), 33-38, 2008-08-21 [Table of Contents]
The Institute of Electronics, Information and Communication Engineers
