Browsing by Subject "Numerical modeling"

Now showing 1 - 4 of 4

Open Access
Hollow-core optical fiber with eight-pointed star cladding structure for low-loss transmission in telecom bands
(Scientific and Technical Research Council of Turkey - TUBITAK,Turkiye Bilimsel ve Teknik Arastirma Kurumu, 2021-04-29) Ordu, Mustafa
In this study, a novel negative curvature hollow-core fiber is proposed for low-loss transmission in the near-infrared region. We numerically investigate the effect of the cladding structure, which is formed of concentrically interlaced squares, to the confinement losses using the finite element modelling. The design has eight cladding tubes with nested elements placed to the outer edge of the tubes. The confinement losses of the interlaced square core fiber is calculated as low as 0.12 dB/km in the range of 1.3 to 1.65 µm. The loss profile of the noncircular core design is comparable with the circular cores, and have improved transmission performance at 1.55 µm. The proposed design can have numerous application areas such as data transmission, nonlinear optics and biochemical sensing.
Open Access
Modeling of droplet motion on textured surfaces
(2021-09) Naji, Mayssam
We describe the motion of a droplet on a textured ratchet track using a non-linear resonator model. A textured ratchet track is composed of semi-circular pillar array that induces a net surface tension gradient on a droplet placed on it. When a vertical vibration is applied, hysteresis is overcome, and the droplet moves towards the local lower energy barrier; however, due to the repetitive structure of texture, it keeps moving until the end of the track. The droplet motion depends on the amplitude and frequency of the vertical oscillation, and this dependence is nonlinear. Therefore, ﬁnding a fully analytical solution to represent this motion is not trivial. Consequently, the droplet motion still remains as a topic that needs further investigation. In this study we elaborate on the utility of double-pendulum as a basis for modeling the droplet motion on surfaces. Similar to the droplet motion, resonators, such as double pendulum, are simple, yet non-linear systems. Moreover, inverted double pendulum motion has key characteristics such as two phase motion and double peak motion, which are also observed in the droplet motion on textured ratchets. In this thesis, data processing models are developed to highlight the similarity between these two systems both qualitatively and quantitatively. After establishing this comparison, a model is proposed that utilizes an inverted double pendulum mounted on a moving cart to successfully simulate the motion of a droplet on a ratchet track. This methodology will lead to developing an accurate droplet-motion modeling approach which will be useful to understand droplet dynamics in more depth.
Open Access
Observation of soliton molecules with independently evolving phase in a mode-locked fiber laser
(2010) Ortaç, B.; Zaviyalov, A.; Nielsen, C.K.; Egorov O.; Iliew, R.; Limpert J.; Lederer F.; Tünnermann, A.
We report the experimental generation of two-soliton molecules in an all-polarization-maintaining ytterbium-doped fiber laser operating in the normal dispersion regime. These molecules exhibit an independently evolving phase and are characterized by a regular spectral modulation pattern with a modulation depth of 80% measured as an averaged value. Moreover, the numerical modeling confirms that the limited modulation depth of the spectrum is caused by the evolution of the phase difference between the pulses. © 2010 Optical Society of America.
Open Access
Theoretical and experimental limits of monodisperse droplet generation
(Elsevier Ltd, 2021-01-16) Ali, Kalantarifard; Elnaz, Alizadeh-Haghighi; Abtin, Saateh; Elbüken, Çağlar
Droplet microfluidic systems are becoming routine in advanced biochemical studies such as single cell gene expression, immuno profiling, precise nucleic acid quantification (dPCR) and particle synthesis. For all these applications, ensuring droplet monodispersity is critical to minimize the uncertainty due to droplet volume variation. Despite the wide usage of droplet-based microfluidic systems, the limit of monodispersity for droplet generation systems is still unknown. Here, we present an analytical approach that takes into account all the system dynamics and internal/external factors that disturb monodispersity. Interestingly, we are able to model the dynamics of a segmented two-phase flow system using a single-phase flow analogy, electron flow, in electrical circuits. We offer a unique solution and design guidelines to ensure ultra-monodisperse droplet generation. Our analytical conclusions are experimentally verified using a T-junction droplet generator. Equally importantly, we show the limiting experimental factors for reaching the theoretical maximum of monodispersity.