Преобразование мод в гибридных волноводных структурах на основе ниобата лития для согласования со стандартным одномодовым оптическим волокном

Topology of a hybrid waveguide device, which performs an effective transformation of a standard gradient titanium in-diffused waveguide mode to a hybrid waveguide mode, is considered. With its help a rather large optical mode with size optimal for coupling with standard single-mode fibers can be converted to a mode with a smaller size. Two the most perspective materials for hybrid waveguide fabrication were considered: silicon and titanium dioxide. The theoretical analysis has shown that transformation efficiency of more than 99% is achievable for waveguide devices based on titanium dioxide with contact lithography resolution.

Pump-probe spectroscopy in gold-garnet magnetoplasmonic metasurfaces

Ultrafast modulation of optical response is realized in a multi-resonant magnetoplasmonic metasurface under resonant femtosecond pump. A saturation of resonant probe transient transmission is shown at dielectric quazi-waveguide mode.

Low-Threshold Nanolaser Based on Hybrid Plasmonic Waveguide Mode Supported by Metallic Grating Waveguide Structure

A high Q-factor of the nanocavity can effectively reduce the threshold of nanolasers. In this paper, a modified nanostructure composed of a silver grating on a low-index dielectric layer (LID) and a high-index dielectric layer (HID) was proposed to realize a nanolaser with a lower lasing threshold. The nanostructure supports a hybrid plasmonic waveguide mode with a very-narrow line-width that can be reduced to about 1.79 nm by adjusting the thickness of the LID/HID layer or the duty ratio of grating, and the Q-factor can reach up to about 348. We theoretically demonstrated the lasing behavior of the modified nanostructures using the model of the combination of the classical electrodynamics and the four-level two-electron model of the gain material. The results demonstrated that the nanolaser based on the hybrid plasmonic waveguide mode can really reduce the lasing threshold to 0.042 mJ/cm2, which is about three times lower than the nanolaser based on the surface plasmon. The lasing action can be modulated by the thickness of the LID layer, the thickness of the HID layer and the duty cycle of grating. Our findings could provide a useful guideline to design low-threshold and highly-efficient miniaturized lasers.

Tackling light trapping in organic light-emitting diodes by complete elimination of waveguide modes

Conventional waveguide mode decoupling methods for organic light-emitting diodes (OLEDs) are typically not scalable and increase fabrication complexity/cost. Indium-tin-oxide–free transparent anode technologies showed efficiency improvement without affecting other device properties. However, previous works lack rigorous analysis to understand the efficiency improvement. Here, we introduced an ultrathin silver (Ag) film as transparent electrode and conducted systematic modal analysis of OLEDs and report that waveguide mode can be completely eliminated by designing an OLED structure that is below the cutoff thickness of waveguide modes. We also experimentally verified the waveguide mode removal in organic waveguides with the help of index-matching fluid and prism. The negative permittivity, extremely thin thickness (~5 nanometers), and highly conductive properties achieved by a uniform copper-seeded Ag film can suppress waveguide mode formation, enhancing external quantum efficiency without compromising any other characteristics of OLEDs, which paves the way for cost-effective high-efficiency OLEDs in current display industry.

Diffraction of a Gaussian Beam with Limited cross Section by a Volume Phase Grating under Waveguide Mode Resonance

In this work, the diffraction of a Gaussian beam on a volume phase grating was researched theoretically and numerically. The proposed method is based on rigorous coupled-wave analysis (RCWA) and Fourier transform. The Gaussian beam is decomposed into plane waves using the Fourier transform. The number of plane waves is determined using the sampling theorem. The complex reflected and transmitted amplitudes are calculated for each RCWA plane wave. The distribution of the fields along the grating for the reflected and transmitted waves is determined using inverse Fourier transform. The powers of the reflected and transmitted waves are determined based on these distributions. Our method shows that the energy conservation law is satisfied for the phase grating. That is, the power of the incident Gaussian beam is equal to the sum of the powers of the reflected and transmitted beams. It is demonstration of our approach correctness. The numerous studies have shown that the spatial shapes of the reflected and transmitted beams differ from the Gaussian beam under resonance. In additional, the waveguide mode appears also in the grating. The spatial forms of the reflected and transmitted beams are Gaussian in the absence of resonance. It was found that the width of the resonance curves is wider for the Gaussian beam than for the plane wave. However, the spectral and angular sensitivities are the same as for the plane wave. The resonant wavelengths are slightly different for the plane wave and the Gaussian beam. Numerical calculations for four refractive index modulation coefficients of the grating medium were carried out by the proposed method. The widths of the resonance curves decrease with the increasing in the refractive index modulation. Moreover, the reflection coefficient also increases.