A broadband and low-power light-control-light effect in a fiber-optic nano-optomechanical system

Dynamics of dual-orbit rotations of nanoparticles induced by spin-orbit coupling

Spin-orbit coupling (SOC) in tightly focused optical fields offers a powerful mechanism for manipulating the complex motion of particles. However, to date, such a mechanism has only been applied to the single-orbit motion for particles, while multi-orbital dynamics have not yet been experimentally demonstrated. Here, the theoretical and experimental realization of dual-orbit rotational dynamics of nanoparticles in a tightly focused circularly polarized Laguerre-Gaussian beam is reported. Analyses reveal that the dual-orbit rotation of nanoparticles originates from SOC in a tightly focused vortex beam, with the motion velocity and direction determined by the topological charge of the beam. Experimentally, the dual-orbit rotation of polystyrene nanoparticles was observed for the first time using an inverted optical tweezer. In addition, the rotation velocity showed a clear linear dependence on the topological charge of the incident beam. This work reveals the pivotal role of SOC in enabling precise dual-orbit control at the nanoscale, paving the way for applications in optical sorting, grinding and delivery of microparticles.

Dynamics of polarization-tuned mirror symmetry breaking in a rotationally symmetric system

Lateral momentum conservation is typically kept in a non-absorptive rotationally symmetric system through mirror symmetry via Noether's theorem when illuminated by a homogeneous light wave. Therefore, it is still very challenging to break the mirror symmetry and generate a lateral optical force (LOF) in the rotationally symmetric system. Here, we report a general dynamic action in the SO(2) rotationally symmetric system, originating from the polarization-tuned mirror symmetry breaking (MSB) of the light scattering. We demonstrate theoretically and experimentally that MSB can be generally applied to the SO(2) rotationally symmetric system and tuned sinusoidally by polarization orientation, leading to a highly tunable and highly efficient LOF (9.22 pN/mW/μm-2) perpendicular to the propagation direction. The proposed MSB mechanism and LOF not only complete the sets of MSB of light-matter interaction and non-conservative force only using a plane wave but also provide extra polarization manipulation freedom.

A lipase-conjugated carbon nanotube fiber-optic SPR sensor for sensitive and specific detection of tributyrin

As a low-density lipoprotein, tributyrin plays an essential role in food safety and human health. In this study, a novel lipase-conjugated carbon nanotube (CNT) surface plasmon resonance (SPR) fiber-optic sensor is used to specifically detect tributyrin for the first time. In this work, CNTs can be used as an amplifying material to significantly increase the sensitivity of SPR sensors due to their high refractive index and large surface area. CNTs can also be used as an enzyme carrier to provide abundant carboxyl groups for the specific binding of lipases. Covering the surface of the sensor with CNTs can not only enhance the performance of the sensor, but also provide sufficient detection sites for subsequent biomass detection, reduce the functionalization steps, and simplify the sensor preparation process. The experimental results demonstrate that the refractive index sensitivity of the traditional multimode fiber (MMF)-single mode fiber (SMF)-MMF transmissive optical fiber sensor is 1705 nm RIU-1. After covering the sensor with CNTs, the sensitivity is 2077 nm RIU-1, and the sensitivity has been improved very well. In addition, there are abundant functional groups on CNTs, which can provide abundant binding sites. Conjugating lipase on carbon nanotubes helps to achieve linear detection in the range of 0.5 mM to 4 mM tributyrin, with a sensitivity of 4.45 nm mM-1 and a detection limit of 0.34 mM, which is below the 2.26 mM detection standard and meets food safety monitoring requirements. Compared with other sensors, the optical fiber biosensor proposed in this study expands the concentration detection range of tributyrin. Furthermore, the sensor also has good stability, anti-interference performance and specificity. Therefore, the sensor proposed in this paper has good application prospects in the fields of food safety and biomedicine.