We propose electrically tunable periodically segmented waveguides (PSW) using liquid crystals in their structure. Duty cycles are varied showing that light diffracts and refocuses periodically through the liquid cryst...
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ISBN:
(数字)9781510628724
ISBN:
(纸本)9781510628724
We propose electrically tunable periodically segmented waveguides (PSW) using liquid crystals in their structure. Duty cycles are varied showing that light diffracts and refocuses periodically through the liquid crystal core PSW, when an external voltage is applied on it. The propagation characteristics are analyzed for different values of effective refractive index, duty cycle and external voltage applied. The liquid crystal core PSW performance analyzed presents a device that can works as a polarizer and mode size converter for transversal mode polarization, an important and desired requisite in photonics circuits devices.
Compact, widely-tunable, continuous-wave (CW) and ultrashort-pulse laser sources in the visible spectral region are extremely valuable in a wide range of cutting-edge applications such as photomedicine, biophotonics a...
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ISBN:
(数字)9781510624474
ISBN:
(纸本)9781510624474
Compact, widely-tunable, continuous-wave (CW) and ultrashort-pulse laser sources in the visible spectral region are extremely valuable in a wide range of cutting-edge applications such as photomedicine, biophotonics and microscopy. The most promising approach to develop a compact, efficient and widely-tunable visible laser source is second harmonic generation (SHG) in a periodically poled nonlinear crystal containing a waveguide, which not only allows highly efficient frequency conversion even at low pump power levels but also offers an order-of-magnitude increase of wavelength range for efficient SHG by the utilization of multi-mode matching technique. In this respect, semiconductor lasers with their small size, high efficiency, reliability, low-cost and wide spectral range coverage are very promising for the realization of tunable visible laser sources. InAs/GaAs quantum-dot (QD) external-cavity diode lasers (ECDLs), owing to the unique features of QDs, are of special interest for that matter. The use of multi-mode matching technique and SHG in periodically-poled potassium titanyl phosphate (PPKTP) waveguides pumped by tunable QD-ECDLs led to the realization of compact, widely-tunable, visible, CW (567.7 - 629.1 nm and 574 - 647 nm) and picosecond-pulse (600 - 627 nm) laser sources. Furthermore, the ability of QD-ECDLs to generate two tunable longitudinal modes simultaneously allowed the demonstration of dual-wavelength SHG (505.4-537.7nm wavelength region) from diode-pumped PPKTP waveguides. In addition, compact CW white-light and multi-color laser sources were demonstrated by the use of two ECDLs and a PPKTP waveguide. The demonstrated laser sources represent an important step towards the realization of a compact, room-temperature, tunable laser source in the visible spectral region.
Neutron optics is the branch of quantum physics devoted to the study of the optical properties of slow neutrons and their behavior as wave-particles. Slow neutrons beams (with typical energy the order of 0.025 eV, kno...
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ISBN:
(数字)9781510631649
ISBN:
(纸本)9781510631649
Neutron optics is the branch of quantum physics devoted to the study of the optical properties of slow neutrons and their behavior as wave-particles. Slow neutrons beams (with typical energy the order of 0.025 eV, known as thermal neutrons, and also smaller) can propagate confined in guides of various transverse dimensions, longitude and geometries, under total internal reflection conditions, like in the case of classical optical waveguides. We study the properties and possible applications of neutron waveguides with small transverse dimensions. In particular, we have implemented a new algorithm to simulate neutron beams as they are confined in particular waveguides. The results, obtained from a new analytical formalism, are compared with standard numerical methods as the FDTD and, then, enhance the feasibility for recreating the beam structure as the later propagates inside the waveguide.
Amorphous photonic materials offer an alternative to photonic crystals as a building block for photonic integrated circuits due to their shared short-range order. By using the inherent disorder of amorphous photonic m...
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ISBN:
(纸本)9781510624719
Amorphous photonic materials offer an alternative to photonic crystals as a building block for photonic integrated circuits due to their shared short-range order. By using the inherent disorder of amorphous photonic materials, it is possible to design flexible-shaped waveguides that are free from restrictions of photonic crystals at various symmetry axes. Effects of disorder on photonic crystal waveguide boundaries have examined before, and it is shown that flexible waveguides with high transmission are possible by forming a wall of equidistant scatterers around the defect created inside amorphous material configuration. Based on this principle, waveguides with various flexible shapes are designed and fabricated for planar circuit applications. A silicon-on-insulator (SOI) slab with random configuration of air hole scatterers is used. The amorphous configuration is generated through realistic Monte Carlo simulations mimicking crystalline-to-amorphous transition of semiconductor crystals via an assigned Yukawa potential to individual particles. The design parameters such as average hole distance, slab thickness and hole radius are adjusted so that the waveguide is utilizable around 1550 nm telecommunications wavelength. Such waveguides on slab structures are characterized here and the level of randomness and band gap properties of amorphous configurations are analyzed in detail. These efforts have the potential to lead easier design of a wide range of components including but not limited to on-chip Mach-Zehnder interferometers, splitters, and Y-branches.
We investigate optical forces between evanescently coupled optical waveguides with balanced gain and loss. This system reveals unusual properties, most notably the emergence of a tangential stress component parallel t...
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ISBN:
(纸本)9781943580576
We investigate optical forces between evanescently coupled optical waveguides with balanced gain and loss. This system reveals unusual properties, most notably the emergence of a tangential stress component parallel to the direction of wave propagation. (c) 2019 The Author(s)
We report the design and fabrication of titanium dioxide optical waveguides optimized for supercontinuum generation in the mid-infrared. A spectrum spanning from the visible up to 2 mu m is experimentally demonstrated...
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ISBN:
(纸本)9781943580576
We report the design and fabrication of titanium dioxide optical waveguides optimized for supercontinuum generation in the mid-infrared. A spectrum spanning from the visible up to 2 mu m is experimentally demonstrated. (c) 2019 The Author(s)
To improve the interactive animated teaching platform developed in the electromagnetics revitalization program in Taiwan, a project was granted by IEEE MTT-S Education Committee under the SIGMA-WE initiative in the en...
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ISBN:
(纸本)9781728140407
To improve the interactive animated teaching platform developed in the electromagnetics revitalization program in Taiwan, a project was granted by IEEE MTT-S Education Committee under the SIGMA-WE initiative in the end of 2018. New interactive web-based learning modules have also been voluntarily developed. Among them, a learning module for metallic rectangular waveguide will be introduced in this paper. This module shows the animation of mode patterns of a rectangular waveguide, such as the electric field of TE10 mode and the magnetic field of TM11 mode. Cut planes to show the field patterns are freely selectable by users. Operating frequency is also a user-input parameters to facilitate the learning of cutoff behavior. The web-based learning module is developed using JavaScript and related cross-browser libraries.
We experimentally demonstrate hybrid photonic-plasmonic waveguides utilizing plasmonic TiN, and index mismatched substrate and superstrate. The design offers lower losses and tighter mode-confinement compared to previ...
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ISBN:
(纸本)9781943580576
We experimentally demonstrate hybrid photonic-plasmonic waveguides utilizing plasmonic TiN, and index mismatched substrate and superstrate. The design offers lower losses and tighter mode-confinement compared to previously reported long-range surface plasmon polariton waveguides using noble metals. (C) 2019 The Author(s)
Since their first demonstration in 2002, terahertz (THz) quantum cascade lasers (QCLs) have proven to be one of the most reliable sources of this type of radiation. Advances have been made in increasing maximum operat...
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Since their first demonstration in 2002, terahertz (THz) quantum cascade lasers (QCLs) have proven to be one of the most reliable sources of this type of radiation. Advances have been made in increasing maximum operating temperature, shaping the beam and tuning the frequency and bandwidth. Waveguide engineering has been a particular area of interest due to the large wavelength of the THz radiation (> 100 μm). This thesis introduces several improvements related to THz QCL waveguide technology. We begin by describing the THz radiation range, its applications and available sources. We then focus on the theoretical framework used to describe and design QCLs. We also review the two main waveguides employed in THz QCLs: the surface plasmon (SP) and the metal-metal (MM) waveguides. We outline the main fabrication steps for both waveguides. Firstly, a novel photonic crystal-based QCL is presented. It comprises a defect line in a triangular lattice of active region (GaAs/AlGaAs) pillars embedded in a polymer matrix. The defects are made of pillars larger than the lattice pillars. Lasing is possible in this device on specific frequency levels (defect modes) within the band gap of the photonic crystal. Emitted frequency can be finely tuned by changing the size of the pillars in the lattice. A non-linear QCL geometry (a 90° junction), which allows for arbitrary emission direction, is also presented. Such waveguides may play an important role in integrated THz circuits. Secondly, a new hybrid plasmonic waveguide for THz QCL is presented. It employs a polymer, benzocyclobutene (BCB), which solidifies upon heating and acts as a bonding agent. This waveguide serves as an alternative to MM and allows for arbitrarily thick metal deposition below the active region. Simulations are presented with an aim to explain the observed beam shape. For two different active regions and different thicknesses of bottom gold layer, a full light-current-voltage, spectral, and far-field characterisati
Data usage continues to rise exponentially with user demand, and the bandwidth of optical communications is reaching its limit. Spectrally efficient advanced modulation formats are being used to increase the data rate...
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Data usage continues to rise exponentially with user demand, and the bandwidth of optical communications is reaching its limit. Spectrally efficient advanced modulation formats are being used to increase the data rate within the existing bandwidth. Mach-Zehnder Modulators achieve high spectral density by modulating both the phase and amplitude of light. At the moment, laser light sources and Mach-Zehnder Modulators are built discretely and packaged and coupled thereafter. Photonic Integrated Circuits (PICs) place multiple photonic components onto single chips, with the benefit of compactness resulting in lower cost through simpler coupling, lower power consumption, and volume manufacture. The difficulty faced by photonic integration is that different components require different material for their different functions, and so cannot be easily placed onto the same material substrate wafer. Existing methods use regrowth techniques to selectively replace material around the chip, but regrowth is expensive and time consuming. This work vertically integrated a passive waveguide above an active waveguide using regrowth-free monolithic integration. The passive and active waveguides are designed for Mach-Zehnder modulator and laser material. The waveguides were processed on an InP platform, and consisted of AlGaInAs alloys. To our knowledge this is the first time a passive waveguide has been vertically integrated above an active waveguide for III-V semiconductors, and the first time two AlGaInAs waveguides have been vertically integrated, using monolithic regrowth-free techniques on InP. Vertical coupling was performed through lateral tapers, and an isolation barrier between the stacked waveguides allows the vertical integration of already optimised discrete components without modification. As the isolation barrier deliberately reduces the coupling between the waveguides away from the transition region, a technique using a third passive waveguide in the barrier was used to i
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