Dispersion Tailoring of the Quarter-Wave Bragg Reflection Waveguide

We present analytical formulae for the polarization dependent first- and second-order dispersion of a quarter-wave Bragg reflection waveguide (QtW-BRW). Using these formulae, we develop several qualitative properties of the QtW-BRW. In particular, we show that the birefringence of these waveguides changes sign at the QtW wavelength. Regimes of total dispersion corresponding to predominantly materialdominated and waveguide-dominated dispersion are identified. Using this concept, it is shown that the QtW-BRW can be designed so as to provide anomalous group velocity dispersion of large magnitude, or very small GVD of either sign, simply by an appropriate chose of layer thicknesses. Implications on nonlinear optical devices in compound semiconductors are discussed

Advances in Optofluidics

Optofluidics a niche research field that integrates optics with microfluidics. It started with elegant demonstrations of the passive interaction of light and liquid media such as liquid waveguides and liquid tunable lenses. Recently, the optofluidics continues the advance in liquid-based optical devices/systems. In addition, it has expanded rapidly into many other fields that involve lightwave (or photon) and liquid media. This Special Issue invites review articles (only review articles) that update the latest progress of the optofluidics in various aspects, such as new functional devices, new integrated systems, new fabrication techniques, new applications, etc. It covers, but is not limited to, topics such as micro-optics in liquid media, optofluidic sensors, integrated micro-optical systems, displays, optofluidics-on-fibers, optofluidic manipulation, energy and environmental applciations, and so on

Sonic and Photonic Crystals

Sonic/phononic crystals termed acoustic/sonic band gap media are elastic analogues of photonic crystals and have also recently received renewed attention in many acoustic applications. Photonic crystals have a periodic dielectric modulation with a spatial scale on the order of the optical wavelength. The design and optimization of photonic crystals can be utilized in many applications by combining factors related to the combinations of intermixing materials, lattice symmetry, lattice constant, filling factor, shape of the scattering object, and thickness of a structural layer. Through the publications and discussions of the research on sonic/phononic crystals, researchers can obtain effective and valuable results and improve their future development in related fields. Devices based on these crystals can be utilized in mechanical and physical applications and can also be designed for novel applications as based on the investigations in this Special Issue

Study of propagation and detection methods of terahertz radiation for spectroscopy and imaging

The applications of terahertz (THz, 1 THz is 1012 cycles per second or 300 pm in wavelength) radiation are rapidly expanding. In particular, THz imaging is emerging as a powerful technique to spatially map a wide variety of objects with spectral features which are present for many materials in THz region. Objects buried within dielectric structures can also be imaged due to the transparency of most dielectrics in this regime. Unfortunately, the image quality in such applications is inherently influenced by the scattering introduced by the sample inhomogeneities and by the presence of barriers that reduces both the transmitted power and the spatial resolution in particular frequency components. For continued development in THz radiation imaging, a comprehensive understanding of the role of these factors on THz radiation propagation and detection is vital. This dissertation focuses on the various aspects like scattering, attenuation, frequency filtering and waveguide propagation of THz radiation and its subsequent application to a stand-off THz interferometric imager under development. Using THz Time Domain spectroscopic set-up, the effect of scattering, guided THz propagation with loss and dispersion profile of hollow-core waveguides and various filtering structures are investigated. Interferometric detection scheme and subsequent agent identification is studied in detail using extensive simulation and modeling of various imaging system parameters

Design, Fabrication, and Demonstration of Square Holey Dielectric THZ Waveguides

A variety of novel dielectric THz waveguides were demonstrated to increase a channel capacity in a chip-to-chip communication system. Square holey cladding dielectric THz waveguides were designed, fabricated, and characterized. The single material holey cladding waveguide is low loss and easy to fabricate compared to doped core fibers. The square geometry supports two states of polarization with minimum cross-talk for polarization division multiplexing applications. Simulations show the waveguide supports two states of polarization across the frequency range of 180 GHz to 360 GHz. In addition, simulations show good mode isolation and low bending losses. Holey cladding square waveguide was fabricated using a custom-built draw tower to preserve the square geometry. TOPAS was chosen from several studied dielectrics for its low material loss and fabrication capabilities. Fabricated waveguides were shown to support the mode despite manufacturing defects. Fiber loss measurements showed a 24 dB/m loss that approach the accepted material loss of TOPAS (22 dB/m). THz vortex waveguides were demonstrated for space division multiplexing applications for the first time. The holey cladding TOPAS-based vortex waveguide was designed to preserve orbital angular momentum for l=1 and 2 at 280 GHz. The output power of the waveguide for different l and core sizes were studied. The waveguide was fabricated with the custom-built draw tower. Transmission of a first order OAM beam at 280 GHz was experimentally demonstrated. The first order, l=1, Laguerre-Gaussian beam was generated with a custom-made spiral phase plate. Inspired by the vortex waveguide design, several low-loss square holey core/cladding waveguides were designed and simulated for polarization division multiplexing. The waveguides combine the benefits of low loss and broadband transmission, while supporting two states of polarization. The boundary conditions created by the holey cladding confine the beam to the holey core for a low loss transmission. Three square holey core/cladding designs were proposed. These designs include a single-hole core, a nine-hole core, and a core comprised of four square capillary tubes. The square capillary tubes exhibits 7 dB/m, which is significantly lower than the material loss of TOPAS (22 dB/m)