A system for generating a uniform evanescent wave field

Abstract

The invention belongs to the technical field of guided wave optics, and particularly relates to a system for generating a uniform evanescent wave field. The system provided by the invention comprises a refractive index gap structure and a light beam guide mechanism; the refractive index gap structure is a planar three-layer structure composed of two flat panel materials having high refractive indexes and trapezoidal cross sections and a low refractive index layer sandwiched between the flat panel materials; a beam of laser is symmetrically guided into the two high refractive index layers in the refractive index gap after being split by the light beam guide mechanism and symmetrically irradiates the interface of the low refractive index layer, and an angle of incidence is equal to a total internal reflection angle; and the strength and phases of the two beams of laser are adjusted by a variable beam splitter and a phase retarder. By adopting the system provided by the invention, the uniform evanescent wave field can be generated in the low refractive index layer, and can be applied to micro-nano structure analysis or sensing application of materials.

Description

technical field [0001] The invention belongs to the technical field of guided wave optics, and in particular relates to a system for generating a uniform evanescent wave field. Background technique [0002] In the microstructure analysis of materials, Raman scattering and fluorescence are two effective analysis methods. With the help of planar optical waveguide technology, the surface evanescent field can be generated to excite the sample to be analyzed. However, since the surface evanescent field is mostly exponentially decaying spatially distributed, it is not uniform, so that the excitation effect is affected by the spatial inhomogeneity. At the same time, due to this exponential attenuation, the effective depth of the evanescent field is very shallow, generally in the order of one wavelength. Therefore, high requirements are placed on the preparation of samples, which also limits the types of samples that can be measured. Therefore, it is urgent to study methods that c...

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Problems solved by technology

However, since the surface evanescent field is mostly exponentially decaying in spatial distribution, it is not uniform, so that the effect of the excitation is affected by the spatial inhomogeneity

At the same time, due to this exponential attenuation, the effective depth of the evanescent field is very shallow, generally in the order of one wavelength. Therefore, high requirements are placed on the preparation of samples, which also limits the types of samples that can be measured.

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