Drying-mediated optical assembly of silica spheres in a symmetrical metallic waveguide structure

Continuous Goos-Hänchen Shift of Vortex Beam via Symmetric Metal-Cladding Waveguide

Goos-Hänchen shift provides a way to manipulate the transverse shift of an optical beam with sub-wavelength accuracy. Among various enhancement schemes, millimeter-scale shift at near-infrared range has been realized by a simple symmetrical metal-cladding waveguide structure owing to its unique ultrahigh-order modes. However, the interpretation of the shift depends crucially on its definition. This paper shows that the shift of a Gaussian beam is discrete if we follow the light peak based on the stationary phase approach, where the M-lines are fixed to specific directions and the beam profile is separated near resonance. On the contrary, continuous shift can be obtained if the waveguide is illuminated by a vortex beam, and the physical cause can be attributed to the position-dependent phase-match condition of the ultrahigh-order modes due to the spatial phase distribution.

Stable directional emission in active optical waveguides shielding external environmental influences

The skillful confinement of light brought by the composite waveguide structure has shown great possibilities in the development of photonic devices. It has greatly expanded the application range of an on-chip system in dark-field imaging and confined the laser when containing an active medium. Here we experimentally proved a stable directional emission in an active waveguide composed of metal and photonic crystal, which is almost completely unaffected by the external environment and different from the common local light field that is seriously affected by the structure. When the refractive index of samples on the surface layer changes, it can ensure the constant emission intensity of the internal mode, while still retaining the external environmental sensitivity of the surface mode. It can also be used for imaging and sensing as a functional slide. This research of chip-based directional emission is very promising for various applications including quantitative detection of biological imaging, coupled emission intensity sensing, portable imaging equipment, and tunable micro lasers.

SERS chip fabricated by the thermal effect in a double-metal-cladding waveguide

Different from ordinary planar waveguide structure, we designed a double-metal-cladding waveguide (DMCW) for easier light coupling into the guiding layer from free space. In contrast to evanescent waves in a surface plasmon polariton waveguide, an oscillating wave is generated in the guiding layer. and a similar Fabry-Perot (FP) cavity can be formed by the DMCW. In past work, the FP cavity excited by the DMCW was used to study the refractive index of light, while in this work, the FP cavity is used to excite the photothermal effect of the metal substrate. It is a good connection between light and heat. The photothermal effect is investigated to promote the galvanic replacement reaction in the substrate. Although the experiment process is destructive to the DMCW structure, a surface-enhanced Raman scattering (SERS) chip is prepared on the basis of the photothermal effect in the DMCW. It shows that the DMCW can convert the energy of incident light into thermal energy, and then prepare the SERS chip. The chip has better uniformity, stronger activity, and higher sensitivity. The results demonstrate that the morphology of the SERS substrate created via the DMCW is far more elaborate than that via the surface plasmon polariton waveguide.