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Hong-chang Yang - One of the best experts on this subject based on the ideXlab platform.

  • Ordered structures with point-like defects of various shapes in magnetic Fluid Films
    Journal of Magnetism and Magnetic Materials, 2004
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    Owing to the increasing importance of the photonic crystals in opto-electronics, the fabrication of ordered structures becomes urgently required. In this work, we report the formation of the two-dimensional hexagonal ordered structure in the highly homogeneous magnetic Fluid film when a magnetic field is applied perpendicularly to the film surface. Furthermore, we investigate the structural patterns when point-like defects of various shapes are introduced artificially into the film. It was found that, for the triangle or the hexagonal defects, a nearly perfect ordered structure is obtained around the defects in the magnetic Fluid film, whereas twin boundaries exist for rectangular defects. The existence of the twin boundaries is attributed to the mismatch in the characterized angles of the rectangular defect (=90°) and the hexagonal ordered structure (=60°) in the magnetic Fluid film. These observed results reveal the promising ordered structures for developing photonic-crystal cavities by using the magnetic Fluid Films with point-like cavities.

  • origin and applications of magnetically tunable refractive index of magnetic Fluid Films
    Applied Physics Letters, 2004
    Co-Authors: Shieh-yueh Yang, Herng-er Horng, Jenje Chieh, Chin Yin Hong, Hong-chang Yang
    Abstract:

    When an external field was applied, the refractive index of the magnetic Fluid film was observed to be modulated as the field exceeded a critical strength. We found that the stronger the magnetic field, the higher the refractive index. By taking both the formation of the columns and the variation in the concentration of the liquid phase in magnetic Fluid Films under external magnetic fields into account, the refractive index was calculated and compared with experimental data. When we did this, we noticed a consistency that implies that the phase separation leads to the variation in the refractive index of the magnetic Fluid film as the magnetic field strength is changed. With such a property as a tunable refractive index, the feasibility of using a magnetic Fluid in a tunable optical device is worthy of investigation.

  • Control parameters for the tunable refractive index of magnetic Fluid Films
    Journal of Applied Physics, 2003
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    In this work, we systematically investigate the influence of control parameters, including the concentration of magnetic particles, film thickness, external field direction, and field sweep rate, on the magnetically tunable refractive index of magnetic Fluid Films. We find that the variation in the refractive index of the magnetic Fluid film with rising field strength is enhanced by increasing either the concentration or the film thickness, or by applying the field along the film surface, whereas it is independent of the sweep rate of the field. The results clearly reveal how to control the tunable refractive index of magnetic Fluid Films. Furthermore, they provide valuable information that may assist in the development of magnetic-Fluid-based index-tunable devices.

  • Tunable CWDM by utilizing ordered structures in magnetic Fluid Films
    CLEO Pacific Rim 2003. The 5th Pacific Rim Conference on Lasers and Electro-Optics (IEEE Cat. No.03TH8671), 2003
    Co-Authors: Shieh-yueh Yang, Chi-yih Hong, Y.w. Huang, Herng-er Horng, Hong-chang Yang
    Abstract:

    With the demand of the development in high-speed telecommunication, the WDM technologies become important and attract lots of interests of scientists and engineers. In this report, we explore a new method to fabricate coarse WDM (CWDM) by utilizing the ordered structure in the magnetic Fluid Films under external magnetic fields. It was found that the first-order interference lights of two incident visible lights with a difference of 20 nm in wavelength can be absolutely separated. This separation was further observed to increase as the incident angle of the light incident into the magnetic Fluid film was raised, whereas the transmittance became lower. Due to the tunability of the ordered structure in the magnetic Fluid film by adjusting the external field strength, the magnetic-Fluid-based CWDM is tunable and the 4-channel tunable CWDM is demonstrated in this work.

  • Magnetically modulated optical transmission of magnetic Fluid Films
    Journal of Magnetism and Magnetic Materials, 2002
    Co-Authors: Herng-er Horng, Shieh-yueh Yang, Hong-chang Yang, W S Tse, Weili Luo, Chin-yih Hong
    Abstract:

    Abstract The optical transmission of the magnetic Fluid film under perpendicular magnetic fields was investigated by measuring the transmitted intensity of the normally incident light through the film. The transmittance I / I 0 of the magnetic Fluid film was observed to decrease with the increase of the magnetic field strength H due to the reduction in the area occupied by the relatively optic transparent liquid phase. Moreover, under a given H , the transmittance decreased exponentially with the increasing film thickness L , i.e. I / I 0 =exp(− L / δ ), where the δ denotes the attenuation distance. It was further found that the δ varies with the magnetic field strength and the concentration of the Fluid, but is independent of the sweep rate of the field.

Shieh-yueh Yang - One of the best experts on this subject based on the ideXlab platform.

  • Ordered structures with point-like defects of various shapes in magnetic Fluid Films
    Journal of Magnetism and Magnetic Materials, 2004
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    Owing to the increasing importance of the photonic crystals in opto-electronics, the fabrication of ordered structures becomes urgently required. In this work, we report the formation of the two-dimensional hexagonal ordered structure in the highly homogeneous magnetic Fluid film when a magnetic field is applied perpendicularly to the film surface. Furthermore, we investigate the structural patterns when point-like defects of various shapes are introduced artificially into the film. It was found that, for the triangle or the hexagonal defects, a nearly perfect ordered structure is obtained around the defects in the magnetic Fluid film, whereas twin boundaries exist for rectangular defects. The existence of the twin boundaries is attributed to the mismatch in the characterized angles of the rectangular defect (=90°) and the hexagonal ordered structure (=60°) in the magnetic Fluid film. These observed results reveal the promising ordered structures for developing photonic-crystal cavities by using the magnetic Fluid Films with point-like cavities.

  • origin and applications of magnetically tunable refractive index of magnetic Fluid Films
    Applied Physics Letters, 2004
    Co-Authors: Shieh-yueh Yang, Herng-er Horng, Jenje Chieh, Chin Yin Hong, Hong-chang Yang
    Abstract:

    When an external field was applied, the refractive index of the magnetic Fluid film was observed to be modulated as the field exceeded a critical strength. We found that the stronger the magnetic field, the higher the refractive index. By taking both the formation of the columns and the variation in the concentration of the liquid phase in magnetic Fluid Films under external magnetic fields into account, the refractive index was calculated and compared with experimental data. When we did this, we noticed a consistency that implies that the phase separation leads to the variation in the refractive index of the magnetic Fluid film as the magnetic field strength is changed. With such a property as a tunable refractive index, the feasibility of using a magnetic Fluid in a tunable optical device is worthy of investigation.

  • Control parameters for the tunable refractive index of magnetic Fluid Films
    Journal of Applied Physics, 2003
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    In this work, we systematically investigate the influence of control parameters, including the concentration of magnetic particles, film thickness, external field direction, and field sweep rate, on the magnetically tunable refractive index of magnetic Fluid Films. We find that the variation in the refractive index of the magnetic Fluid film with rising field strength is enhanced by increasing either the concentration or the film thickness, or by applying the field along the film surface, whereas it is independent of the sweep rate of the field. The results clearly reveal how to control the tunable refractive index of magnetic Fluid Films. Furthermore, they provide valuable information that may assist in the development of magnetic-Fluid-based index-tunable devices.

  • Tunable CWDM by utilizing ordered structures in magnetic Fluid Films
    CLEO Pacific Rim 2003. The 5th Pacific Rim Conference on Lasers and Electro-Optics (IEEE Cat. No.03TH8671), 2003
    Co-Authors: Shieh-yueh Yang, Chi-yih Hong, Y.w. Huang, Herng-er Horng, Hong-chang Yang
    Abstract:

    With the demand of the development in high-speed telecommunication, the WDM technologies become important and attract lots of interests of scientists and engineers. In this report, we explore a new method to fabricate coarse WDM (CWDM) by utilizing the ordered structure in the magnetic Fluid Films under external magnetic fields. It was found that the first-order interference lights of two incident visible lights with a difference of 20 nm in wavelength can be absolutely separated. This separation was further observed to increase as the incident angle of the light incident into the magnetic Fluid film was raised, whereas the transmittance became lower. Due to the tunability of the ordered structure in the magnetic Fluid film by adjusting the external field strength, the magnetic-Fluid-based CWDM is tunable and the 4-channel tunable CWDM is demonstrated in this work.

  • magnetically modulated refractive index of magnetic Fluid Films
    Applied Physics Letters, 2002
    Co-Authors: Shieh-yueh Yang, Chin-yih Hong, Herng-er Horng, Yute Chen, W S Tse, H C Yang
    Abstract:

    We developed a setup to probe the refractive index of the magnetic Fluid Films under external magnetic fields. This setup possesses a high resolution of 0.0001 in the measured refractive index. It was found that the refractive index of the magnetic Fluid depends linearly on the concentration of the dilute magnetic Fluid under zero field. For a given magnetic Fluid film, the refractive index increases with the increasing field strength over a critical value, and then becomes saturated as the field reaches around 200 Oe. It is noteworthy that the magnetically modulated refractive index of the magnetic Fluid Films could have great potential in electro-optical applications.

Herng-er Horng - One of the best experts on this subject based on the ideXlab platform.

  • Ordered structures with point-like defects of various shapes in magnetic Fluid Films
    Journal of Magnetism and Magnetic Materials, 2004
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    Owing to the increasing importance of the photonic crystals in opto-electronics, the fabrication of ordered structures becomes urgently required. In this work, we report the formation of the two-dimensional hexagonal ordered structure in the highly homogeneous magnetic Fluid film when a magnetic field is applied perpendicularly to the film surface. Furthermore, we investigate the structural patterns when point-like defects of various shapes are introduced artificially into the film. It was found that, for the triangle or the hexagonal defects, a nearly perfect ordered structure is obtained around the defects in the magnetic Fluid film, whereas twin boundaries exist for rectangular defects. The existence of the twin boundaries is attributed to the mismatch in the characterized angles of the rectangular defect (=90°) and the hexagonal ordered structure (=60°) in the magnetic Fluid film. These observed results reveal the promising ordered structures for developing photonic-crystal cavities by using the magnetic Fluid Films with point-like cavities.

  • origin and applications of magnetically tunable refractive index of magnetic Fluid Films
    Applied Physics Letters, 2004
    Co-Authors: Shieh-yueh Yang, Herng-er Horng, Jenje Chieh, Chin Yin Hong, Hong-chang Yang
    Abstract:

    When an external field was applied, the refractive index of the magnetic Fluid film was observed to be modulated as the field exceeded a critical strength. We found that the stronger the magnetic field, the higher the refractive index. By taking both the formation of the columns and the variation in the concentration of the liquid phase in magnetic Fluid Films under external magnetic fields into account, the refractive index was calculated and compared with experimental data. When we did this, we noticed a consistency that implies that the phase separation leads to the variation in the refractive index of the magnetic Fluid film as the magnetic field strength is changed. With such a property as a tunable refractive index, the feasibility of using a magnetic Fluid in a tunable optical device is worthy of investigation.

  • Control parameters for the tunable refractive index of magnetic Fluid Films
    Journal of Applied Physics, 2003
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    In this work, we systematically investigate the influence of control parameters, including the concentration of magnetic particles, film thickness, external field direction, and field sweep rate, on the magnetically tunable refractive index of magnetic Fluid Films. We find that the variation in the refractive index of the magnetic Fluid film with rising field strength is enhanced by increasing either the concentration or the film thickness, or by applying the field along the film surface, whereas it is independent of the sweep rate of the field. The results clearly reveal how to control the tunable refractive index of magnetic Fluid Films. Furthermore, they provide valuable information that may assist in the development of magnetic-Fluid-based index-tunable devices.

  • Tunable CWDM by utilizing ordered structures in magnetic Fluid Films
    CLEO Pacific Rim 2003. The 5th Pacific Rim Conference on Lasers and Electro-Optics (IEEE Cat. No.03TH8671), 2003
    Co-Authors: Shieh-yueh Yang, Chi-yih Hong, Y.w. Huang, Herng-er Horng, Hong-chang Yang
    Abstract:

    With the demand of the development in high-speed telecommunication, the WDM technologies become important and attract lots of interests of scientists and engineers. In this report, we explore a new method to fabricate coarse WDM (CWDM) by utilizing the ordered structure in the magnetic Fluid Films under external magnetic fields. It was found that the first-order interference lights of two incident visible lights with a difference of 20 nm in wavelength can be absolutely separated. This separation was further observed to increase as the incident angle of the light incident into the magnetic Fluid film was raised, whereas the transmittance became lower. Due to the tunability of the ordered structure in the magnetic Fluid film by adjusting the external field strength, the magnetic-Fluid-based CWDM is tunable and the 4-channel tunable CWDM is demonstrated in this work.

  • magnetically modulated refractive index of magnetic Fluid Films
    Applied Physics Letters, 2002
    Co-Authors: Shieh-yueh Yang, Chin-yih Hong, Herng-er Horng, Yute Chen, W S Tse, H C Yang
    Abstract:

    We developed a setup to probe the refractive index of the magnetic Fluid Films under external magnetic fields. This setup possesses a high resolution of 0.0001 in the measured refractive index. It was found that the refractive index of the magnetic Fluid depends linearly on the concentration of the dilute magnetic Fluid under zero field. For a given magnetic Fluid film, the refractive index increases with the increasing field strength over a critical value, and then becomes saturated as the field reaches around 200 Oe. It is noteworthy that the magnetically modulated refractive index of the magnetic Fluid Films could have great potential in electro-optical applications.

Chin-yih Hong - One of the best experts on this subject based on the ideXlab platform.

  • Ordered structures with point-like defects of various shapes in magnetic Fluid Films
    Journal of Magnetism and Magnetic Materials, 2004
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    Owing to the increasing importance of the photonic crystals in opto-electronics, the fabrication of ordered structures becomes urgently required. In this work, we report the formation of the two-dimensional hexagonal ordered structure in the highly homogeneous magnetic Fluid film when a magnetic field is applied perpendicularly to the film surface. Furthermore, we investigate the structural patterns when point-like defects of various shapes are introduced artificially into the film. It was found that, for the triangle or the hexagonal defects, a nearly perfect ordered structure is obtained around the defects in the magnetic Fluid film, whereas twin boundaries exist for rectangular defects. The existence of the twin boundaries is attributed to the mismatch in the characterized angles of the rectangular defect (=90°) and the hexagonal ordered structure (=60°) in the magnetic Fluid film. These observed results reveal the promising ordered structures for developing photonic-crystal cavities by using the magnetic Fluid Films with point-like cavities.

  • Control parameters for the tunable refractive index of magnetic Fluid Films
    Journal of Applied Physics, 2003
    Co-Authors: Chin-yih Hong, Shieh-yueh Yang, Herng-er Horng, Hong-chang Yang
    Abstract:

    In this work, we systematically investigate the influence of control parameters, including the concentration of magnetic particles, film thickness, external field direction, and field sweep rate, on the magnetically tunable refractive index of magnetic Fluid Films. We find that the variation in the refractive index of the magnetic Fluid film with rising field strength is enhanced by increasing either the concentration or the film thickness, or by applying the field along the film surface, whereas it is independent of the sweep rate of the field. The results clearly reveal how to control the tunable refractive index of magnetic Fluid Films. Furthermore, they provide valuable information that may assist in the development of magnetic-Fluid-based index-tunable devices.

  • magnetically modulated refractive index of magnetic Fluid Films
    Applied Physics Letters, 2002
    Co-Authors: Shieh-yueh Yang, Chin-yih Hong, Herng-er Horng, Yute Chen, W S Tse, H C Yang
    Abstract:

    We developed a setup to probe the refractive index of the magnetic Fluid Films under external magnetic fields. This setup possesses a high resolution of 0.0001 in the measured refractive index. It was found that the refractive index of the magnetic Fluid depends linearly on the concentration of the dilute magnetic Fluid under zero field. For a given magnetic Fluid film, the refractive index increases with the increasing field strength over a critical value, and then becomes saturated as the field reaches around 200 Oe. It is noteworthy that the magnetically modulated refractive index of the magnetic Fluid Films could have great potential in electro-optical applications.

  • Magnetically modulated optical transmission of magnetic Fluid Films
    Journal of Magnetism and Magnetic Materials, 2002
    Co-Authors: Herng-er Horng, Shieh-yueh Yang, Hong-chang Yang, W S Tse, Weili Luo, Chin-yih Hong
    Abstract:

    Abstract The optical transmission of the magnetic Fluid film under perpendicular magnetic fields was investigated by measuring the transmitted intensity of the normally incident light through the film. The transmittance I / I 0 of the magnetic Fluid film was observed to decrease with the increase of the magnetic field strength H due to the reduction in the area occupied by the relatively optic transparent liquid phase. Moreover, under a given H , the transmittance decreased exponentially with the increasing film thickness L , i.e. I / I 0 =exp(− L / δ ), where the δ denotes the attenuation distance. It was further found that the δ varies with the magnetic field strength and the concentration of the Fluid, but is independent of the sweep rate of the field.

  • magnetochromatics resulted from optical gratings of magnetic Fluid Films subjected to perpendicular magnetic fields
    Journal of Applied Physics, 2000
    Co-Authors: H E Horng, Shieh-yueh Yang, Chin-yih Hong, S L Lee, Hong-chang Yang
    Abstract:

    A two-dimensional ordered structure can be formed in a thin film of homogeneous magnetic Fluids by applying a magnetic field perpendicular to the plane of the film. The characteristic spacing of the ordered structure can be controlled by several parameters, such as the field strength, the sweep rate, the thickness of the film, and the volume concentration of homogeneous magnetic Fluids. The length of the characteristic spacing ranges from several micrometers to submicrometers. Depending on the size of the spacing, magnetic Fluid Films are capable of diffracting an incoming white light. The diffracted light then interferes resulting in a chromatic effect. This effect is well illustrated by the chromatic rings produced by passing a white light through the magnetic Fluid Films possessing an ordered structure. Because of the changeability of the characteristic spacing, the magnetochromatic effect of magnetic Fluid Films can be controlled by altering these control parameters.

Lou Kondic - One of the best experts on this subject based on the ideXlab platform.

  • stability of thin Fluid Films characterised by a complex form of effective disjoining pressure
    Journal of Fluid Mechanics, 2018
    Co-Authors: Michaelangelo Y H Lam, L J Cummings, Lou Kondic
    Abstract:

    We discuss instabilities of Fluid Films of nanoscale thickness, with a particular focus on Films where the destabilising mechanism allows for linear instability, metastability, and absolute stability, depending on the mean film thickness. Our study is motivated by nematic liquid crystal Films; however, we note that similar instability mechanisms, and forms of the effective disjoining pressure, appear in other contexts, such as the well-studied problem of polymeric Films on two-layered substrates. The analysis is carried out within the framework of the long-wave approximation, which leads to a fourth-order nonlinear partial differential equation for the film thickness. Within the considered formulation, the nematic character of the film leads to an additional contribution to the disjoining pressure, changing its functional form. This effective disjoining pressure is characterised by the presence of a local maximum for non-vanishing film thickness. Such a form leads to complicated instability evolution that we study by analytical means, including the application of marginal stability criteria, and by extensive numerical simulations that help us develop a better understanding of instability evolution in the nonlinear regime. This combination of analytical and computational techniques allows us to reach novel understanding of relevant instability mechanisms, and of their influence on transient and fully developed Fluid film morphologies. In particular, we discuss in detail the patterns of drops that form as a result of instability, and how the properties of these patterns are related to the instability mechanisms.

  • stability of thin Fluid Films characterised by a complex form of structural effective disjoining pressure
    arXiv: Soft Condensed Matter, 2017
    Co-Authors: Michaelangelo Y H Lam, L J Cummings, Lou Kondic
    Abstract:

    We discuss instabilities of Fluid Films of nanoscale thickness, with a particular focus on Films where the destabilising mechanism allows for linear instability, metastability, and absolute stability. Our study is motivated by nematic liquid crystal Films; however we note that similar instability mechanisms, and forms of the effective disjoining pressure, appear in other contexts, such as the well-studied problem of polymeric Films on two-layered substrates. The analysis is carried out within the framework of the long-wave approximation, which leads to a fourth order nonlinear partial different equation for the film thickness. Within the considered formulation, the nematic character of the film leads to an additional contribution to the disjoining pressure, changing its functional form. This effective disjoining pressure is characterised by the presence of a local maximum for non-vanishing film thickness. Such a form leads to complicated instability evolution that we study by analytical means, including application of marginal stability criteria, and by extensive numerical simulations that help us develop a better understanding of instability evolution in the nonlinear regime. This combination of analytical and computational techniques allows us to reach novel understanding of relevant instability mechanisms, and of their influence on transient and fully developed Fluid film morphologies.

  • instability of nanometric Fluid Films on a thermally conductive substrate
    Physical Review Fluids, 2016
    Co-Authors: Nanyi Dong, Lou Kondic
    Abstract:

    The dynamics of a thin, incompressible viscous Fluid, subject to both van der Waals and Marangoni forces, on a thermally conducting substrate, is theoretically considered in the regime where the temperature field of the film and of the substrate evolve on a comparable time scale. Calculations show that the Marangoni flows have a strong effect on the instability and that the evolution of the temperature field, coupled to the evolving film profile, qualitatively changes the instability.

  • instability of nanometric Fluid Films on a thermally conductive substrate
    arXiv: Soft Condensed Matter, 2016
    Co-Authors: Nanyi Dong, Lou Kondic
    Abstract:

    We consider thin Fluid Films placed on thermally conductive substrates and exposed to time-dependent spatially uniform heat source. The evolution of the Films is considered within the long-wave framework in the regime such that both Fluid/substrate interaction, modeled via disjoining pressure, and Marangoni forces, are relevant. We analyze the problem by the means of linear stability analysis as well as by time-dependent nonlinear simulations. The main finding is that when self-consistent computation of the temperature field is performed, a complex interplay of different instability mechanisms results. This includes either monotonous or oscillatory dynamics of the free surface. In particular, we find that the oscillatory behavior is absent if the film temperature is assumed to be slaved to the current value of the film thickness. The results are discussed within the context of liquid metal Films, but are of relevance to dynamics of any thin film involving variable temperature of the free surface, such that the temperature and the film interface itself evolve on comparable time scales.

  • on the breakup of Fluid Films of finite and infinite extent
    Physics of Fluids, 2007
    Co-Authors: Javier A Diez, Lou Kondic
    Abstract:

    We study the dewetting process of thin Fluid Films that partially wet a solid surface. Using a long-wave (lubrication) approximation, we formulate a nonlinear partial differential equation governing the evolution of the film thickness, h. This equation includes the effects of capillarity, gravity, and an additional conjoining/disjoining pressure term to account for intermolecular forces. We perform standard linear stability analysis of an infinite flat film, and identify the corresponding stable, unstable, and metastable regions. Within this framework, we analyze the evolution of a semi-infinite film of length L in one direction. The numerical simulations show that for long and thin Films, the dewetting fronts of the film generate a pearling process involving successive formation of ridges at the film ends and consecutive pinch-off behind these ridges. On the other hand, for shorter and thicker Films, the evolution ends up by forming a single drop. The time evolution as well as the final drops pattern sho...