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Development of Easily Phase-Matchable Wavelength-Conversion Devices Due to Fabrication of Periodically Polarization-Inverted Structures Using Organic Nonlinear-Optical Crystals.

由于使用有机非线性光学晶体制造周期性偏振反转结构，开发了易于相位匹配的波长转换器件。

基本信息

批准号：
05555016
负责人：
UMEGAKI Shinsuke
金额：
$ 7.81万
依托单位：
Keio University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

The research mainly consists of two parts. One is to exploit nonlinear-optical organic materials transparent enough in the visible region and the other is to realize quasi-phase-matching (QPM) in second-harmonic generation (SHG) for organic crystals which possess higher figures of merit due to their constituent molecules oriented parallel to each other.In the former part, we could overcome the trade-off between the cutoff wavelength or the maximum-absorption wavelength and the figures of merit in the previous organic materials. Using the hyper Rayleigh scattering method, we studied aromatic ions with a viewpoint of their ionic polarizabilities in addition to the internal charge-transfer. We compared the ionic species with the corresponding neutral derivatives and found that the former molecules have the 1st hyperpolarizabilities several times larger than the latter ones for given maximum-absorption wavelengths. We expect that those molecules will be effectively used in crystals and/or polymers.In the latter part, we could successfully achieve the QPM guided-wave SHG using the organic 2-methyl-4-nitroaniline (MNA). Since the molecules of MNA are oriented nearly parallel to each other and aligned in the crystallographic X-axis, the largest coefficient d_<11> cannot be phase-matched by birefringence and cannot be effectively used by the Cerenkov-radiation type phase-matching. We proposed to use QPM for the organic crystals mentioned above. Generally speaking, however, the coherence lengths are too short to produce periodic structures for QPM.In the research, we sdopted planar waveguides, in which the coherence lengths can be elongated. We could grow ridge-shaped single crystals on glass substrates with a period of 5 micrometer. As a result, we could realize the QPM SHG by angle tuning to the coherence legth.

本研究主要由两部分组成。一种是利用在可见光范围内足够透明的非线性光学有机材料，另一种是对有机晶体的二次谐波(SHG)实现准相位匹配(QPM)，因为有机晶体的组成分子相互平行而具有较高的品质因数。利用超瑞利散射方法，我们从离子极化率和内部电荷转移的角度研究了芳香族离子。我们比较了离子物种和相应的中性衍生物，发现在给定的最大吸收波长下，前者的第一超极化率比后者大几倍。我们期望这些分子能够有效地应用于晶体和/或聚合物中。在后半部分，我们可以成功地利用有机2-甲基-4-硝基苯胺(MNA)实现准PM导波倍频。由于MNA分子几乎相互平行，且沿晶体X轴排列，因此最大系数d11不能用双折射进行位相匹配，也不能被切伦科夫辐射型位相匹配有效地利用。我们建议对上述有机晶体采用准相位调制。然而，通常情况下，相干长度太短，不能产生周期结构。在研究中，我们采用了可以延长相干长度的平面光波导。我们可以在玻璃衬底上生长出周期为5微米的脊状单晶。因此，我们可以通过角度调谐到相干光束来实现准PM倍频。