N Konopsky Valery, V Alieva Elena, Yu Alyatkin Sergey, A Melnikov Alexey, V Chekalin Sergey, M Agranovich Vladimir
Institute of Spectroscopy, Fizicheskaya, 5, Troitsk, Moscow 142190, Russia.
Moscow Institute of Physics and Technology, Institutskiy per., 9, Dolgoprudny 141700, Russia.
Light Sci Appl. 2016 Nov 4;5(11):e16168. doi: 10.1038/lsa.2016.168. eCollection 2016 Nov.
Efficient nonlinear conversion requires that interacting optical waves maintain a consistent phase relationship when traveling in a medium despite its dispersion. Birefringent phase-matching, which is often used to compensate for the dispersion, is not applicable to optically isotropic nonlinear materials. Here, we present a one-dimensional photonic crystal structure that allows the propagation of optical surface waves, both at the fundamental and third-harmonic frequencies, as an efficient medium for phase-matched third-harmonic generation. A unique advantage of this structure is that the effective refractive indices for the surface waves are similar to the refractive index of air at both frequencies. This allows phase-matching between the first and third harmonics, and a visible collinear beam of the third harmonic is produced at the prism-coupled output. Moreover, these optical surface waves propagate over long distances even if a lossy nonlinear nanofilm is deposited onto the photonic crystal surface. We provide experimental results for third-harmonic generation at a wavelength of 410 nm for a bare dielectric TaO/SiO multilayer structure and for the same structure coated with a 15-nm GaAs film.
高效的非线性转换要求相互作用的光波在介质中传播时，尽管存在色散，仍能保持一致的相位关系。常用于补偿色散的双折射相位匹配不适用于光学各向同性的非线性材料。在此，我们展示了一种一维光子晶体结构，它允许光学表面波在基频和三倍频频率下传播，作为一种用于相位匹配三倍频产生的有效介质。这种结构的一个独特优势在于，表面波在两个频率下的有效折射率都与空气的折射率相似。这使得基波和三倍频之间能够实现相位匹配，并且在棱镜耦合输出端产生可见的共线三倍频光束。此外，即使在光子晶体表面沉积了有损非线性纳米薄膜，这些光学表面波仍能长距离传播。我们给出了裸介电TaO/SiO多层结构以及涂覆有15nm GaAs薄膜的相同结构在波长为410nm时三倍频产生的实验结果。
