The optical field enhanced nonlinear optical (NLO) absorption of spin-coated 10-layer and 20-layer 1D photonic crystal structures is demonstrated. A significant 2.5 fold increase in the two-photon absorption coefficient is reported for multilayer structures as compared to a single layer of semiconductor nanocomposite (NC) having a comparable thickness. Under high-intensity illuminance, increased nonlinear absorption could be accredited to the confinement of the optical field due to the localization of intensity. The carefully engineered multilayer structures embedded with semiconductor NCs can provide an attractive approach to designing practical NLO limiters and switches.

Silicon nitride (SiN) has been receiving increased attention for photonic integrated circuits (PICs) due to its ultra-low optical losses, phase stability, and broadband transparency. However, SiN waveguides have a low thermo-optic coefficient and exhibit weak electro-optic effects. For this reason, most foundry-processed SiN PICs remain passive or exhibit inefficient tuning. In this work, we investigate polymer claddings to enhance the thermo-optic phase shifting in foundry-processed low-loss, thin core SiN PICs. We first develop a thermal testing setup and measure the response of standard foundry SiN / SiO₂ waveguides. By taking advantage of the differing TE and TM modal overlap with the SiN core and SiO₂ cladding, we extract the LPCVD-SiN thermo-optic coefficient as dn_SiN / dT = 2.57 × 10 ^{− 5} / ° C at λ = 1550 nm and dn_SiN / dT = 2.82 × 10 ^{− 5} / ° C at λ = 780 nm. We next consider SiN waveguides in which the top SiO₂ cladding is replaced with a spin-coated thermo-optic polymer. The thin waveguide core (t_SiN = 150 to 220 nm) enables a weakly confined mode with a large overlap with the top polymer cladding. Measurements at λ = 780 nm wavelength show up to a 12-fold improvement in the thermo-optic phase shift of these polymer-cladded SiN waveguides compared with SiO₂ cladded devices while inducing negligible excess loss. Finally, we show broadband Mach–Zehnder interferometer measurements demonstrating thermo-optic tuning at visible wavelengths. The simple spin-coat post-processing of foundry SiN PICs in this work offers a potential path toward efficient optical phase shifting in low-loss SiN waveguides over a broad wavelength range

A one-dimensional multilayer structure consisting of two symmetric parts with defect layers is designed, and properties of the multiple nonreciprocal transmission are investigated due to symmetrically distributed magneto-optic layers with opposite magnetic fields in composite structures. The transmission coefficient and energy band diagram of the system are obtained based on transfer matrix method. The numerical results show that there are three pairs of nonreciprocal dispersive curves with different modes in a certain bandgap. The influence of the thickness of defect layer and incident angle on nonreciprocal frequencies is also discussed. The multiple nonreciprocal transmission could in turn be potentially useful in optical isolators and optical resonators.

Detectors with cost-effective, polarization-sensitive, and integrative functionalities are required for next-generation ultraviolet (UV) detection systems. Low-dimensional semiconductor materials have potential for optical device applications, especially polarization detection, because of their excellent polarization characteristics. Therefore, ultralong ZnO microwires, ∼0.5 to 1 cm long, were prepared using the chemical vapor-phase epitaxy method, making it easy to build photoelectric devices. The emission polarization of the ZnO microwires excited by circularly polarized light was ∼0.60, indicating a high-anisotropy optical property. Their UV-polarization spectrum and photoelectric detection were determined. When the ZnO microwire was excited by linearly polarized UV light, the intensity of photoluminescence (PL) changed periodically with the polarization direction of the UV light. The PL polarization of the ZnO microwire for linear UV detection was ∼0.12. For a ZnO microwires photoelectric device, the photocurrent anisotropy ratio reached 1.28 when the polarization angle of the incident UV light changed. These results suggest that the obtained ultralong ZnO microwires have the potential for application in future UV-polarization detection systems.

At present, an all optical high-order tunable ordinary differential equation (ODE) solver is very difficult to implement. A novel all-optical first to third order linear ODEs solutions with tunable constant coefficients using double Sagnac rings coupled Mach–Zehnder-interferometer (DSMZI) on silicon waveguide chips are proposed. The structural composition and size of the DSMZI have been designed, and the working principles of its first to third order ODEs solutions have been derived. By varying the input electric heating power of the thermal-optical phase shifters of the individual arms of the MZI, the constant-coefficient of the differential equation can be simply tuned in large scope. It is demonstrated that the constant coefficient k ranges from 0.0015/ps to 0.092/ps for the first-order ODE. The constant coefficient p of the second-order ODE solver can be continuously tuned from 0.013/ps to 0.174/ps, correspondingly with the q varying from 0.00004225/ps2 to 0.007569/ps2. Three constant coefficients u, v, and w of the third-order ODE can be continuously tuned from 0.105/ps to 0.252/ps, 0.003675/ps2 to 0.021168/ps2, and 0.00004288/ps3 to 0.0005927/ps3, respectively. The all-optical ODE solvers with the DSMZI can be easily integrated with other optical components based on silicon on insulator, which can provide a path for future artificial intelligence or big data processing systems in optical computing on silicon waveguide chips.

Microresonators have been extensively studied in integrated photonics over the past two decades. However, the thermal frequency drift of a resonator limits its applications in practice. Athermal microresonators, as a passive solution, have become highly attractive. We propose two types of broadband athermal waveguides, with three zero-thermal-drift wavelengths achieved through mode anti-crossing effect, for the first time. For the polymer-coated waveguide, the effective thermo-optical coefficient (TOC) has a variation of ±1.5×10−6/K from 1350 to 1790 nm. For the TiO2-coated waveguide, the effective TOC has a variation of ±1.5×10−6/K from 1510 to 2090 nm. Over such a wide band of 440 or 580 nm, both the athermal microring resonators show excellent athermal property of <1 pm/K. The broadband athermal characteristics of the resonators would enable a wide variety of applications, e.g., wavelength-division multiplexing filters, modulators, lasers, sensors, and nonlinear optical sources.