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Following the intensive development of isolated (i.e., not coupled with on-chip waveguide) vertically rolled-up microtube ring resonators (VRU-MRRs) for both active and passive applications, a variety of microtube-based devices has been realized. These include microcavity lasers, optical sensors, directional couplers, and active elements in lab-on-a-chip devices. To provide more advanced and complex functionality, the focus of tubular geometry research is now shifting toward (i) refined vertical light transfer in 3D stacks of multiple photonic layers and (ii) to make microfluidic cooling system in the integrated optoelectronic system. Based on this motivation, this PhD research is devoted to the demonstration and the implementation of monolithic integration of VRU-MRRs with photonic waveguides for 3D photonic integration and their optofluidic applications. Prior to integration, high-quality isolated VRU-MRRs on the flat Si substrate are firstly fabricated by the controlled release of differentially strained titanium-dioxide (TiO2) bilayered nanomembranes. The fabricated microtubes support resonance modes for both telecom and visible photonics. The outcome of the isolated VRU-MRRs is a record high Q (≈3.8×10^3) in the telecom wavelength range with optimum tapered optical fiber resonator interaction. To further study the optical modes in the visible and near infrared spectral range, μPL spectroscopy is performed on the isolated VRU-MRRs, which are activated by entrapping various sizes of luminescent nanoparticles (NPs) within the windings of rolled-up nanomembranes based on a flexible, robust and economical method. Moreover, it is realized for the first time, in addition to serving as light sources that NPs-aggregated in isolated VRU-MRRs can produce an optical potential well that can be used to trap optical resonant modes. After achieving all the required parameters for creating a high-quality TiO2 VRU-MRR, the monolithic integration of VRU-MRRs with Si nanophotonic

Following the intensive development of isolated (i.e., not coupled with on-chip waveguide) vertically rolled-up microtube ring resonators (VRU-MRRs) for both active and passive applications, a variety of microtube-based devices has been realized. These include microcavity lasers, optical sensors, directional couplers, and active elements in lab-on-a-chip devices. To provide more advanced and complex functionality, the focus of tubular geometry research is now shifting toward (i) refined vertical light transfer in 3D stacks of multiple photonic layers and (ii) to make microfluidic cooling system in the integrated optoelectronic system. Based on this motivation, this PhD research is devoted to the demonstration and the implementation of monolithic integration of VRU-MRRs with photonic waveguides for 3D photonic integration and their optofluidic applications. Prior to integration, high-quality isolated VRU-MRRs on the flat Si substrate are firstly fabricated by the controlled release of differentially strained titanium-dioxide (TiO2) bilayered nanomembranes. The fabricated microtubes support resonance modes for both telecom and visible photonics. The outcome of the isolated VRU-MRRs is a record high Q (≈3.8×10^3) in the telecom wavelength range with optimum tapered optical fiber resonator interaction. To further study the optical modes in the visible and near infrared spectral range, μPL spectroscopy is performed on the isolated VRU-MRRs, which are activated by entrapping various sizes of luminescent nanoparticles (NPs) within the windings of rolled-up nanomembranes based on a flexible, robust and economical method. Moreover, it is realized for the first time, in addition to serving as light sources that NPs-aggregated in isolated VRU-MRRs can produce an optical potential well that can be used to trap optical resonant modes. After achieving all the required parameters for creating a high-quality TiO2 VRU-MRR, the monolithic integration of VRU-MRRs with Si nanophotonic

Because of its unique properties, titania (TiO2) represents a promising candidate in a wide variety of research fields. In this paper, some of the properties and potential applications of titania within rolled-up nanotechnology are explored. It is shown how the structural and optical properties of rolled titania microtubes can be controlled by properly tuning the microfabrication parameters. The rolling up of titania films on different sacrificial layers and containing different shapes, achieving a control on the diameter of the fabricated titania microtubes, is presented. In order to obtain the more photoactive crystalline form of titania, one during-fabrication and two post-fabrication methods are demonstrated. Interesting applications in the fields of photocatalysis and photonics are suggested: the use of titania rolled-up microtubes as micromotors and optical microresonators is presented., Postprint (published version)

In this paper, the torque, reorientation and the change in angular momentum of the light are firstly discussed. And moreover, the propagation of light beam (optical spatial soliton beam) at the distance of a few millimeters in chiral nematic liquid crystal (CNLC) will be experimentally under study. In spite of the complex structure of these crystals, due to a self-focusing effect, by injection of infrared laser beam with a power of the order of a few tenths of milliwatts into CNLC an optical spatial soliton beam is observed. In addition, we experimentally obtain the formation of splitting of a soliton beam into two soliton beams which have equal powers due to a saturation of the reorientational nonlinearity. As a matter of fact, this saturation of the reorientational nonlinearity can occur at one point of CNLC, due to the nonlocal nonlinearity. Hence this saturation of the reorientation nonlinearity can split one soliton beam to two soliton beams. This splitting can have a great potential interest for applications in all-optical signal processing, reconfigurable optical interconnects and switching.

The Publisher would like to inform the readers that the names of the second and third authors of this article have been misprinted in the original article. The correct names of the authors are as follows: Jeroen Beeckman Kristiaan Neyts We apologize for any inconvenience this error may have caused.

Liquid crystals (LC) are anisotropic materials which experience a torque if an electric field is present. This field can be due to an external voltage or to the presence of a light beam. Reorientation due to light leads to non-linear behavior in the optical behavior. Due to this kind of nonlinearity therefore it is possible to generate optical spatial soliton beam in LC by bias voltage or without it and interestingly chiral nematic liquid crystals has a opportunity to generate spatial optical solitons without the need for a bias voltage. In this paper we also demonstrate that a sharp switching of the helix structure occurs when the spatial soliton is launched in the middle of two regions where soliton generation is favorable. Due to the optical nonlinearity, the helical structure becomes asymmetric and a sharp switching in one direction can be obtained. Moreover, in this paper, the torque and reorientation of the liquid crystal and the change in angular momentum of the light are discussed. Crown Copyright © 2013 Published by Elsevier GmbH. All rights reserved.

In this work we present numerical results on the propagation of high power laser beams in nematic liquid crystals. The optical nonlinearity of the liquid crystal gives rise to self-focusing and the generation of spatial optical solitons. We consider only configurations in which no bias voltage is necessary for the generation of the spatial optical soliton. One of the configurations considered here is one where the liquid crystal twists along the thickness of the layer over an angle of 180°. This configuration leads to spiraling solitons when the beam is injected with a certain offset with respect to the middle of the liquid crystal layer. The sign of the initial angle of the beam is depending on the sign of the offset. © 2010 SPIE., SCOPUS: cp.p, info:eu-repo/semantics/published

In this work we present numerical results on the propagation of high power laser beams in nematic liquid crystals. The optical nonlinearity of the liquid crystal gives rise to self-focusing and the generation of spatial optical solitons. We consider only configurations in which no bias voltage is necessary for the generation of the spatial optical soliton. One of the configurations considered here is one where the liquid crystal twists along the thickness of the layer over an angle of 180°. This configuration leads to spiraling solitons when the beam is injected with a certain offset with respect to the middle of the liquid crystal layer. The sign of the initial angle of the beam is depending on the sign of the offset. © 2010 SPIE.

In this work we present numerical results on the propagation of high power laser beams in nematic liquid crystals. The optical nonlinearity of the liquid crystal gives rise to self-focusing and the generation of spatial optical solitons. We consider only configurations in which no bias voltage is necessary for the generation of the spatial optical soliton. One of the configurations considered here is one where the liquid crystal twists along the thickness of the layer over an angle of 180°. This configuration leads to spiraling solitons when the beam is injected with a certain offset with respect to the middle of the liquid crystal layer. The sign of the initial angle of the beam is depending on the sign of the offset. © 2010 SPIE., SCOPUS: cp.p, info:eu-repo/semantics/published

Liquid crystals can switch under influence of an electric field or under influence of incident light. In this paper we provide a mathematical description including electrical, optical and elastic torques. Depending on the applied voltage and the incident light, bistability in the director orientation may be possible. Under certain conditions, the sequence of applying incident TM polarized light and a static voltage allows to access different states. © 2009 SPIE.