Features of the Resonance in a Rectangular Dielectric Surace-Relief Gratings Illuminated with a Limited Cross Section Gaussian Beam

In this work the features of the resonance in a rectangular dielectric surface-relief gratings, illuminated with a limited cross-section Gaussian beam, have been studied. The rigorous coupled wave method and beam decomposition into the plane waves by the Fourier transform have been used. It is shown that there is a resonant wavelength for each thickness of the dielectric grating. The value of resonant wavelength depends on the beam angle of incidence on the gratings. Moreover, the two types of resonances can occur in the grating at certain grating parameters. The power reflection coefficient is practically equal to unity for the first type of resonance and is much smaller than unity, for the second one. The obtained results extend the knowledge regarding the nature of the waveguide resonance in the dielectric grating, considering the limited cross section beam, and they can increase its use in many applications.

Nonlinear TMOKE enhancement in 1D Au/Py magnetoplasmonic crystals

Resonant optical properties of the magnetoplasmonic crystals, which support propagation of surface plasmon polaritons (SPPs) accompanied by magnetooptical effects, have found success in magnetic field driven control of optical radiation. In this work we investigate the resonant magnetooptical effects in the second harmonic generation in the magnetoplasmonic crystal formed by gold/pemalloy bifilm covering dielectric grating. Strong transverse magnetooptical Kerr with the contrast up to 30% is revealed in the spectral vicinity of the SPP excitation.

Fabry–Perot Resonance in 2D Dielectric Grating for Figure of Merit Enhancement in Refractive Index Sensing

We have recently reported in our previous work that one-dimensional dielectric grating can provide an open structure for Fabry–Perot mode excitation. The grating gaps allow the sample refractive index to fill up the grating spaces enabling the sample to perturb the Fabry–Perot mode resonant condition. Thus, the grating structure can be utilized as a refractive index sensor and provides convenient sample access from the open end of the grating with an enhanced figure of merit compared to the other thin-film technologies. Here, we demonstrate that 2D grating structures, such as rectangular pillars and circular pillars, can further enhance refractive index sensing performance. The refractive index theory for rectangular pillars and circular pillars are proposed and validated with rigorous coupled wave theory. An effective refractive index theory is proposed to simplify the 2D grating computation and accurately predict the Fabry–Perot mode positions. The 2D gratings have more grating space leading to a higher resonant condition perturbation and sensitivity. They also provide narrower Fabry–Perot mode reflectance dips leading to a 4.5 times figure of merit enhancement than the Fabry–Perot modes excited in the 1D grating. The performance comparison for thin-film technologies for refractive index sensing is also presented and discussed.

Beam generator of 4-channel with zeroth order suppressed by reflective T-type grating

Four-port beam splitter with good uniformity was proposed by T-type double-layer with different dielectric grating. The total efficiency of the beam splitter is over 90% with beam splitting uniformity better than 3%. At the same time, the simplified modal analysis is added to calculate the grating mode and effective refractive index of the grating area, which clearly describes the physical propagation mechanism inside the grating. The finite element method is used to investigate the normalized field of the grating, which more intuitively reflects the way of energy transfer inside the grating. Finally, the incident characteristics and manufacturing tolerance of the grating are analyzed. Properties of the T-type grating were analyzed in three methods, which more fully illustrates the applicability and stability of the grating in this paper.