Optical phase conjugation based on a ferroelectric semiconductor

通信波长1.55μm的光折变非线性混频已经得到了深入的研究，因为它使我们有可能与光纤相结合来展示光束合成、光束清理和光学相位共轭。由于传统的铁电材料，即掺Rh的BaTiO_3材料在该波长下的光折变灵敏度很低，因此在该波长下的光折变研究主要是在半导体中进行的。然而，为了获得高效的光折变两波混频增益，CdTe：V需要额外的大交流电场(0.4KV/cm)和1.3μm的激发光。在本工作中，我们研究了铁电半导体材料亚硫代二磷酸锡(Sn2P2S6，SPS)的1.55μm光折变相位共轭，它具有相对较窄的禁带(~2.3 eV)、高的电荷迁移率和较大的介电常数。

Photorefractive nonlinear wave mixing at the telecommunication wavelength 1.55 μm has been intensely investigated, because it enables us potentially to demonstrate beam combination, beam cleanup, and optical phase conjugation in combination with fiber optics. Photorefraction at this wavelength regime has been investigated mostly in semiconductors such as CdTe : V, since conventional ferroelectric materials, i.e., Rh doped BaTiO_3 has property of very poor photorefractive sensitivity at this wavelength. However, the CdTe : V requires an additional large alternating current (AC) electric field (.4 kV/cm) and 1.3 μm stimulating illumination to achieve an efficient photorefractive two wave mixing gain.In this work, we investigate 1.55 μm photorefractive phase conjugation in a ferroelectric semiconductor material, tin thiohypodiphosphate (Sn_2P_2S_6, SPS), showing a relatively narrow band gap (～2.3 eV), a high charge mobility, as well as a large dielectric constant.