Plasmonic petal-shaped beam for microscopic phase-sensitive SPR biosensor with ultrahigh sensitivity

Differential phase measurement between radially polarized (RP) and azimuthally polarized (AP) beams is an important technique in microscopic surface plasmon resonance (SPR) biosensors as reported in our earlier works [Opt. Lett. 37, 2091 (2012); Appl. Phys. Lett. 102, 011114 (2013)]. However, such a technique suffers complex beam splitting, detection, and data processing procedures for RP and AP beams which may lower the accuracy of phase measurement. In this Letter, a novel plasmonic petal-shaped vector beam is proposed instead of RP and AP beams, greatly simplifying the sensor system and enabling single measurement in differential interferometry. Moreover, an improved ultrahigh sensitivity on the order of 10−7 refractive index units (RIUs) is experimentally verified in the proposed system.Published versio

Dynamic plasmonic beam shaping by vector beams with arbitrary locally linear polarization states

Vector beams, which have space-variant state of polarization (SOP) comparing with scalar beams with spatially homogeneous SOP, are used to manipulate surface plasmon polarizations (SPPs). We find that the excitation, orientation, and distribution of the focused SPPs excited in a high numerical aperture microscopic configuration highly depend on the space-variant polarization of the incident vector beam. When it comes to vector beam with axial symmetry, multi-foci of SPPs with the same size and uniform intensity can be obtained, and the number of foci is depending on the polarization order n. Those properties can be of great value in biological sensor and plasmonic tweezers applications.ImPhys/Imaging PhysicsApplied Science

The multi-consecutive optical bottles generated from the chirped elliptical Pearcey Gaussian vortex beams

The evolution of the chirped elliptical Pearcey Gaussian vortex (CEPGV) beams in free space is numerically investigated. The optical bottle and multi-consecutive optical bottles can be directly generated from an elliptical Pearcey Gaussian beam with central vortices and the second-order chirp. In particular, the focusing intensity of CEPGV beams will increase when the elliptical structure deflects larger or the ratio of the long axis to the short axis of the ellipse is larger. Furthermore, we can obtain multi-consecutive optical bottles by manipulating elliptical structure parameters and second-order chirp factors. In the meantime, the transverse intensity distributions at foci of CEPGV beams appear like a slit in a fixed direction. Our results show that the focusing intensity, the focal length and the transverse intensity distribution of CEPGV beams during the propagation can be controlled

Nonlinearity-modulated single molecule trapping and Raman scattering analysis

Single molecule detection and analysis play important roles in many current biomedical researches. The deep-nanoscale hotspots, being excited and confined in a plasmonic nanocavity, make it possible to simultaneously enhance the nonlinear light-matter interactions and molecular Raman scattering for label-free detections. Here, we theoretically show that a nanocavity formed in a tip-enhanced Raman scattering (TERS) system can also achieve valid optical trapping as well as TERS signal detection for a single molecule. In addition, the nonlinear responses of metallic tip and substrate film can change their intrinsic physical properties, leading to the modulation of the optical trapping force and the TERS signal. The results demonstrate a new degree of freedom brought by the nonlinearity for effectively modulating the optical trapping and Raman detection in single molecule level. This proposed platform also shows a great potential in various fields of research that need high-precision surface imaging.ImPhys/Optic

Subwavelength spinning of particles in vector cosine-Gaussian field with radial polarization

A new type of radially polarized (RP) cosine-Gaussian (CG) field is proposed. Through the analytical model, it is found that such RP CG beam exhibits completely different focusing properties from the reported RP plane waves. More importantly, a stable three-dimensional trap of Rayleigh particle accompanied by a subwavelength spin motion can be easily achieved using this RP CG beam.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ImPhys/Optic