Impact of nonlocal response in plasmonic metasurfaces on four-wave mixing

We report the impact of nonlocal response in metallic nanostructures on four-wave mixing (FWM) process in nonlinear plasmonic metasurfaces which consist of Au nanostrips coupled with Au film spaced by an ultrathin dielectric film. When the dielectric film is linear and FWM only from the Au nanostructures, the FWM efficiency of around two orders of magnitude enhancement is obtained when the nonlocal effect of Au, not the traditionally local Drude model of Au, is considered. However, when the dielectric film is nonlinear and FWM from the Au nanostructures is negligible, the almost half FWM response from the nonlinear metasurface under the nonlocal, not the local model, of Au is confirmed. These results are both ascribed to the different local electric field distributions near the surface of Au nanostructures and in the gap at the local and nonlocal response of Au. The results have an important significance to design ultra-compacted integrated nonlinear optical devices or to explain the experimental measurements of nonlinear response involving plasmonic nanostructures of ultra-small gaps.

Tuning the Electronic and Nonlinear Optical Properties of (4-Methylphenyl) (4-methylpiperidin-1-yl) Methanone and Its Substituted Analogues

A lot of molecules have been reported for certain applications. However, the need to continuously search for novel materials with more promise is very important because of the competitive technological innovations. One of the ways to achieve this is to use valid theoretical methods that can effectively and accurately predict the properties of existing molecular entities and using these methods to predict the properties of hypothetical molecules. The compound (4-methylphenyl) (4-methylpiperidin-1-yl) methanone (MPMPM) has been reported for its nonlinear optical potentials; however, investigating their reactivity indices would lead to the understanding of the mechanism behind their suitability as nonlinear optical devices. The molecular backbone of MPMPM was altered by introducing some substituents that could alter molecular properties. MPMPM and its derivatives were, therefore, optimized with density functional theory and the time-dependent density functional theory using pure and hybrid correlations and a polar basis set, 6-31G(d). The energy band gaps of the substituted derivatives were lower than that of MPMPM while the dipole moments and hyperpolarizabilities were higher, indicating that they could serve as better alternatives for nonlinear optical applications.

Aluminium nitride integrated photonics: a review

Integrated photonics based on silicon has drawn a lot of interests, since it is able to provide compact solution for functional devices, and its fabrication process is compatible with the mature complementary metal-oxide-semiconductor (CMOS) fabrication technology. In the meanwhile, silicon material itself has a few limitations, including an indirect bandgap of 1.1 eV, transparency wavelength of >1.1 μm, and insignificant second-order nonlinear optical property. Aluminum nitride (AlN), as a CMOS-compatible material, can overcome these limitations. It has a wide bandgap of 6.2 eV, a broad transparency window covering from ultraviolet to mid-infrared, and a significant second-order nonlinear optical effect. Furthermore, it also exhibits piezoelectric and pyroelectric effects, which enable it to be utilized for optomechanical devices and pyroelectric photodetectors, respectively. In this review, the recent research works on integrated AlN photonics in the past decade have been reviewed and summarized. The related material properties of AlN have been summarized and presented. After that, the demonstrated functional devices, including linear optical devices, optomechanical devices, emitters, photodetectors, metasurfaces, and nonlinear optical devices, are reviewed and presented. Last but not the least, the summary and future outlook for the AlN-based integrated photonics are provided.

Optical nonlinearity of zeolitic imidazolate framework-67 in the near-infrared region

Optical nonlinearities of zeolitic imidazolate framework-67 (ZIF-67) were determined in the near-infrared region. The high TPA cross section and large third-order susceptibility demonstrate the potential of ZIF-67 for nonlinear optical devices.

Vertically-oriented MoS2 nanosheets for nonlinear optical devices

We demonstrate a novel strategy for large-area fabrication of vertical MoS2 exhibiting enhanced non-linear optical signal for applications in photonics.