Investigation of surface plasmons in Kretschmann structure loaded with a silver nano-cube

A composite structure based on a Kretschmann structure loaded with silver nano-cube is proposed. A 442-nm laser was used to excite surface plasmons in the composite structure, and the electric field enhancement was numerically simulated using the finite element method. The excitation angles of surface plasmons under conditions of different thicknesses of a PMMA film were obtained by studying the reflection spectrum of the Kretschmann structure. By examining the extinction spectra of silver nano-cubes of different sizes, its optimal size was selected, which is 70 nm. The electric field enhancement factors of the composite structure and the composite PMMA-spaced silver nano-cube and silver film structure were compared in detail. The results show that the coupling of localized surface plasmons and propagating surface plasmons produced by the proposed composite structure mean that its electric field enhancement factor is significantly greater. Moreover, the electric field enhancement factor can be further improved by adding another laser to irradiate the composite structure symmetrically. The high electric field enhancement generated by the composite structure indicates that it has considerable application prospects in surface-enhanced Raman scattering. Keywords: Surface plasmons, Silver nano-cube, Electric field enhancement facto

Theoretical Investigation of a Highly Sensitive Refractive-Index Sensor Based on TM0 Waveguide Mode Resonance Excited in an Asymmetric Metal-Cladding Dielectric Waveguide Structure

This study proposes a highly sensitive refractive-index (RI) sensor based on a TM0 waveguide mode resonance excited in an asymmetric metal-cladding dielectric waveguide structure, where the analyte serves as the guiding layer. By scanning the wavelength at fixed angles of incidence, the reflection spectra of the sensor were obtained. The results showed that the resonance wavelength redshifted dramatically with increases in the analyte RI, which indicates that this approach can be used to sense both the resonance wavelength and the analyte RI. Based on this approach, we investigated the sensing properties, including the sensitivity and figure of merit, at fixed incident angles of 60° and 45°, at which the sensitivity of the sensor reached 7724.9 nm/RIU (refractive index units) and 1339 nm/RIU, respectively. Compared with surface plasmon resonance sensors, which are based on a similar structure, the proposed sensor can accept a more flexible range of incident angles and a wider sensing range of analyte RI. This approach thus has tremendous potential for use in numerous sensing domains, such as biochemical and medical analyses

Investigation of wide-range refractive index sensor based on asymmetric metal-cladding dielectric waveguide structure

A refractive index (RI) sensor based on an asymmetric metal-cladding dielectric waveguide structure, in which an analyte is used as the guiding layer, is proposed in this report. The angular scanning attenuated total reflection spectra of the sensor and optical field distributions under waveguide mode resonance conditions were simulated, which confirmed that multiple waveguide modes can be used for sensing, and that different waveguide modes exist in different analyte RI ranges. The curves of both waveguide mode resonance angles and the sensitivity as a function of the analyte RI demonstrated that a wide sensing range can be achieved by combining waveguide modes of different orders. The proposed sensor could be applied to numerous fields, such as biological and chemical detection

Theoretical investigation of subwavelength structure fabrication based on multi-exposure surface plasmon interference lithography

We propose a method of fabricating subwavelength structures based on multi-exposure surface plasmon interference lithography. This new nanolithography technique fabricates various subwavelength structures breaking the diffraction limit, which differs from the common method of writing various micro structures by using a two-laser-beam interference with sample rotation. Analysis of the optical field distributions obtained using the proposed nanolithography technique, which was performed using the theory of surface plasmon interference lithography in combination with coordinate matrix transformation, is also provided. Various special subwavelength structures are demonstrated by presenting simulated optical field distributions corresponding to different sample rotations, including two-dimensional lattice structures and periodic quasi-hexagonal structures. These structures are potentially useful in micro- and nano-optics applications. Keywords: Nanolithography, Subwavelength structures, Surface plasmon interference, Sample rotatio

Efficient Editing of the ZBED6-Binding Site in Intron 3 of IGF2 in a Bovine Model Using the CRISPR/Cas9 System

Background: Insulin-like growth factor 2 is a growth-promoting factor that plays an important role in the growth and development of mammals. A nucleotide substitution in intron 3 of IGF2—which disrupts the ZBED6-binding site—affects muscle mass, organ size, and fat deposition in pigs. The ZBED6-binding site is also conserved in cattle. Methods: In the present study, we introduced mutations in the ZBED6-binding site in intron3 of IGF2 in bovine fetal fibroblasts using the CRISPR/Cas9 system, and investigated the effect of disruption of ZBED6 binding on IGF2 expression. Results: Eleven biallelic-mutant single-cell clones were established, three of which contained no foreign DNA residues. Single-cell clones 93 and 135 were used to produce cloned embryos. Dual-luciferase reporter assay in C2C12 cells demonstrated that the mutation in the ZBED6-binding site increases the promoter 3 activity of bovine IGF2. A total of 49 mutant cloned embryos were transplanted into surrogate cows. Unfortunately, all cloned embryos died before birth. IGF2 was found to be hypomethylated in the only fetus born (stillborn), which may have been due to the incomplete reprogramming. Conclusions: We efficiently constructed IGF2-edited cell lines and cloned embryos, which provided a theoretical basis and experimental materials for beef cattle breeding