arXiv subjects

Hui An

Publications and source records attributed to Hui An.

4 recordsLinked to original sources

arXiv2025

Controllable Bistability in Dual-Fiber Optical Trap in Air

The dual-fiber optical trap, owing to its high sensitivity and facile miniaturization, holds significant actual application value in fields such as high-precision metrology of mechanical quantities and biological manipulation. The positional stability of the trapped particle is pivotal to system performance, directly setting the measurement noise floor and operational precision. In this work, we observe bistability and hysteresis in the axial equilibrium position of a 10-um diameter SiO2 microsphere. This bistability arises from optical interference between the fiber ends and the microsphere, creating multiple potential wells. Experimental results demonstrate that the microsphere's transition rate can be effectively modulated through precise control of the trapping laser power. Furthermore, the incorporation of transverse misalignment has effectively eradicated bistability, thereby substantially improving positional stability throughout the entire optical trapping region. This suppression successfully reduced the system's residual positional uncertainty to the thermal noise limit. Consequently, this research will enhance the precision of microparticle manipulation and the sensitivity of sensing in dual-fiber optical trap systems.

physics.optics↗

arXiv2023

Effects of detection-beam focal offset on displacement detection in optical tweezers

A high-resolution displacement detection can be achieved by analyzing the scattered light of the trapping beams from the particle in optical tweezers. In some applications where trapping and displacement detection need to be separated, a detection beam can be introduced for independent displacement detection. However, the detection beam focus possibly deviates from the centre of the particle, which will affect the performance of the displacement detection. In this paper, we detect the radial displacement of the particle by utilizing the forward scattered light of the detection beam from the particle. The effects of the lateral and axial offsets between the detection beam focus and the particle centre on the displacement detection are analyzed by the simulation and experiment. The results show that the lateral offsets will decrease the detection sensitivity and linear range and aggravate the crosstalk between the x-direction signal and y-direction signal of QPD. The axial offsets also affect the detection sensitivity, an optimal axial offset can improve the sensitivity of the displacement detection substantially. In addition, the influence of system parameters, such as particle radius a, numerical aperture of the condenser NAc and numerical aperture of the objective NAo on the optimal axial offset are discussed. A combination of conventional optical tweezers instrument and a detection beam provides a more flexible working point, allowing for the active modulation of the sensitivity and linear range of the displacement detection. This work would be of great interest for improving the accuracy of the displacement and force detection performed by the optical tweezers.

physics.optics↗

arXiv2010

Titanium-capped carbon chains as promising new hydrogen storage media

The capacity of Ti-capped sp carbon atomic chains for use as hydrogen storage media is studied using first-principles density functional theory. The Ti atom is strongly attached at one end of the carbon chains via d-p hybridization, forming stable TiCn complexes. We demonstrate that the number of adsorbed H2 on Ti through Kubas interaction depends upon the chain types. For polyyne (n even) or cumulene (n odd) structures, each Ti atom can hold up to five or six H2 molecules, respectively. Furthermore, the TiC5 chain effectively terminated on a C20 fullerene can store hydrogen with optimal binding of 0.52 eV/H2. Our results reveal a possible way to explore high-capacity hydrogen storage materials in truly one-dimensional carbon structures.

cond-mat.mtrl-sci↗

arXiv2010

Realization of high-capacity hydrogen storage using carbon atomic chains: the role of terminations

The capacity of carbon atomic chains with different terminations for hydrogen storage is studied using first-principles density functional theory calculations. Unlike the physisorption of H2 on the H-terminated chain, we show that two Li (Na) atoms each capping one end of the carbon chain can hold ten H2 molecules with optimal binding energies for room temperature storage. The hybridization of the Li 2p states with the H2 sigma orbitals contributes to the H2 adsorption. However, the binding mechanism of the H2 molecules on Na arises only from the polarization interaction between the charged Na atom and the H2. Moreover, additional H2 molecules can be bound to the carbon atoms at the chain ends due to the charge transfer between Li 2s2p (Na 3s) and C 2p states. Importantly, dimerization of these isolated metal-capped chains does not affect the hydrogen binding energy significantly. In addition, a single chain can be stabilized effectively by termination on the C60 clusters. With a hydrogen uptake of > 10 wt % on Li-coated C60-Cn-C60 (n = 5, 8), the Li12C60-Cn-Li12C60 complex, without reducing the number of adsorbed H2 molecules per Li, can serve as better building blocks of polymers than the (Li12C60)2 dimer. These findings suggest a new route to design cluster-assembled storage materials based on terminated sp carbon chains.

cond-mat.mes-hall↗