arXiv subjects

Mohammad Ismail Zibaii

Publications and source records attributed to Mohammad Ismail Zibaii.

3 recordsLinked to original sources

arXiv2026

Laser-Direct-Written polymer WGM microring laser integrated on a fiber tip for refractive index sensing

Whispering-gallery-mode (WGM) microlasers are promising for refractometric sensing, but their practical implementation can be limited by the need for stable resonator-coupler alignment. Here, we demonstrate a Rhodamine B-doped polymer WGM microring laser directly fabricated on an optical-fiber tip, eliminating the external resonator-fiber coupling interface at the sensing head. Micro-droplet coating and UV laser direct writing are combined for fabrication, while finite-difference time-domain simulations guide the microring laser design. The microlasers operate in air and water with thresholds of 0.224 uJ and 0.458 uJ, respectively. Refractometric measurements in aqueous glucose solutions yield a bulk refractive index sensitivity of 364.95 nm/RIU and a detection limit of 2.47 x 10^(-4) RIU. Water-induced polymer changes and photobleaching are also investigated. This fiber-tip architecture provides a basis for probe-based refractometric sensing in environmental and biochemical applications.

physics.optics↗

arXiv2024

Optical signal recording of cellular activity in optogenetic stimulation of human pulp dental cells using a twin-core fiber-based Mach-Zehnder interferometer biosensor

This paper introduces an innovative two-core fiber (TCF) optic sensor employing a Mach-Zehnder interferometer (MZI) to monitor the optogenetic response of light-sensitive human dental pulp stem cells (hDPSCs). The in-fiber MZI, formed using a segment of TCF optic, detects refractive index (RI) changes in the surrounding medium. The sensor utilizes the evanescent wave of one core as the sensing arm, necessitating a thin cladding achieved through one-sided chemical etching. This design allows the sensor to detect subtle alterations in the RI of the environment by observing displacements in the interference spectrum. The optogenetic stimulation of light-sensitive cells induces variations in ion concentrations, leading to a corresponding change in refractive index. The fabricated sensor, with a peak sensitivity of 675.74 nm/RIU within the RI range of 1.39-1.43, can detect these changes. A computer simulation validated the sensitivity and optimized fabrication parameters, exhibiting satisfactory agreement with experimental results. Spectrum displacements were recorded for both light-sensitive hDPSCs and regular hDPSCs (as a control test). Results from the experiment, analyzed and compared using data analysis software, revealed that 473 nm blue light effectively stimulated light-sensitive hDPSCs. Notably, the proposed sensor, a novel structure, demonstrated its capability to detect RI changes in the cell medium during optogenetic applications.

physics.optics↗

arXiv2016

Dynamics of magnetic nano-flake vortices in Newtonian fluids

We study the rotational motion of nano-flake ferromagnetic discs suspended in a Newtonian fluid, as a potential material owing the vortex-like magnetic configuration. Using analytical expressions for hydrodynamic, magnetic and Brownian torques, the stochastic angular momentum equation is determined in the dilute limit conditions under applied magnetic field. Results are compared against experimental ones and excellent agreement is observed. We also estimate the uncertainty in the orientation of the discs due to the Brownian torque when an external magnetic field aligns them. Interestingly, this uncertainty is roughly proportional to the ratio of thermal energy of fluid to the magnetic energy stored in the discs. Our approach can be implemented in many practical applications including biotechnology and multi-functional fluidics.

cond-mat.stat-mech↗