Surface Plasmon Polaritonic Crystals for Applications in Optical communications

The integration and reduction in the photonic device sizes are essential for the development of applications in short-range interconnects and optical signal processing. Surface plasmon polaritonic crystals (SPPCs) can allow the manipulation of optical information in the microscale level, by coupling photons with collective electron oscillations at a metal–dielectric interface. This thesis investigates, both numerically and experimentally, the excitation and propagation of the surface plasmon polaritonic (SPP) modes on finite-size SPPCs, their dependence on the nanostructured geometry and the potential applications in implementing different device functions including SPP-beam shaping, such as focusing and splitting, and wavelength/polarisation demultiplexing. By controlling the SPPC geometry and the excitation beam parameters, directional control of propagating plasmonic modes properties, such as the beam direction, focusing power and beam width, can be achieved. The wavelength-dependent SPP signal spatial separation, due to coupling to the several eigenmodes, and the reduction of the cross-talk by combining polarisation and wavelength modulation have also been shown. In addition, a compact 4-level polarisation discriminator based on a planar, microscale-scale SPPC was developed as part of the research. Its capability to spatially separate linearly polarised signals with azimuth angles 0o , 45o , 90o and 135o , and define the S1 and S2 stokes parameters of any elliptical polarisation state was demonstrated and experimentally tested. The concept was extended to propose a fibre-coupled polarimeter, able to identify the three Stokes vectors parameters, based on the combination of the SPPC with a high -birefringence fibre. The use of SPPCs for the implementation and miniaturisation of key optical communication functionalities, in-plane plasmonic beam manipulation and polarisation/wavelength dependent SPP beam propagation, demonstrated in this work can be important for the development of novel integrated nanophotonic functionalities for subwavelength management of optical signals and the design of a new family of compact devices for optical communication applications

Novel Specialty Optical Fibers and Applications

Novel Specialty Optical Fibers and Applications focuses on the latest developments in specialty fiber technology and its applications. The aim of this reprint is to provide an overview of specialty optical fibers in terms of their technological developments and applications. Contributions include:1. Specialty fibers composed of special materials for new functionalities and applications in new spectral windows.2. Hollow-core fiber-based applications.3. Functionalized fibers.4. Structurally engineered fibers.5. Specialty fibers for distributed fiber sensors.6. Specialty fibers for communications

Near-infrared and mid-infrared integrated silicon devices for chemical and biological sensing

textSilicon has been the material of choice of the photonics industry over the last decade due to its easy integration with silicon electronics as well as its optical transparency in the near-infrared telecom wavelengths. Besides these, it has very high refractive index, and also a broad optical transparency window over the entire mid-IR till about 8[Mu]m. Photonic crystal is well known that it can slow down the speed of light. It also can provide a universal platform for microcavity optical resonators with high quality factor Q and small modal volumes. The slow light effect, high Q and small modal volumes enhance light-matter interaction, together with high refractive index of silicon can be utilized to build a highly sensitive, high throughput sensor with small footprint. In this research, we have demonstrated highly compact and sensitive silicon based photonic crystal biosensor by engineering the photonic crystal microcavity in both cavity size and cavity-waveguide coupling condition. We have developed solutions to increase biosensor throughput by integrating multimode interference device and improving the coupling efficiency to a slow light photonic crystal waveguides. We have also performed detailed investigations on silicon based photonic devices at mid-infrared region to develop an ideal platform for highly sensitive optical absorption spectroscopy on chip. The studies have led to the demonstration of the first slot waveguide, the first photonic crystal waveguide, and the first holey photonic crystal waveguide and first slotted photonic crystal waveguide in silicon-on-sapphire at mid-infrared. The solutions and devices we developed in our research could be very useful for people to realize an integrated photonic circuit for biological and chemical sensing in the future.Electrical and Computer Engineerin

Development of an integrated microspectrometer using arrayed waveguide grating (AWG)

With non-invasive properties and high sensitivities, portable optical biosensors are extremely desirable for point-of-care (POC) applications. Lab-on-a-chip technology such as microfluidics has been treated as an ideal approach to integrate complex sample processing and analysis units with optical detection elements. Spectroscopic sensing (such as fluorescence, Raman and absorption spectroscopy) remains the most highly developed, widely applied, optical technique. However, conventional spectroscopic sensing systems still rely on bulky and expensive dispersive components such as spectrophotometers in a well established laboratory. The work in this thesis is to develop an integrated dispersive component in combination with a microfluidic chip, providing a portable and inexpensive platform for on-chip spectroscopic sensing. In this study, an arrayed waveguide grating (AWG) design developed for telecommunication is re-engineered and utilized to realise a compact, dispersive optical component operating in the visible spectral region. The AWG devices operating in the visible region (λ_c=680 nm) are designed and fabricated with flame hydrolysis deposited (FHD) silica waveguide material. The micro-spectrometer in this proof of concept study has a small (1 cm x 1 cm) footprint and 8 output channels centred on different wavelengths. A series of fabrication issues and challenges are investigated and discussed for the specific AWG device. Subsequently, a sample cuvette is formed by using lithographic technique and dry etching process. Following this, a PDMS chip with microfluidic channels is bonded with the AWG device, leading to an integrated AWG-microfluidic platform. To the best of the author’s knowledge, this is the first work to integrate a visible AWG device and a microfluidic chip towards spectroscopic sensing. The monolithic integrated AWG microspectrometer–microfluidic platform is demonstrated for fluorescence spectroscopic analysis. Signals from the output channels detected on a camera chip can be used to re-create the complete fluorescence spectrum of an analyte. By making fluorescence measurements of (i) mixed quantum dot solutions, (ii) an organic fluorophore (Cy5) and (iii) the propidium iodide (PI)-DNA assay, the results obtained illustrate the unique advantages of the AWG platform for simultaneous, quantitative multiplex detection and its capability to detect small spectroscopic shifts. Although the current system is designed for fluorescence spectroscopic analysis, in principle, it can be implemented for other types of analysis, such as Raman spectroscopy. Fabricated using established semiconductor industry methods, this miniturised platform holds great potential to create a handheld, low cost biosensor with versatile detection capability. Also, the AWG device design is modified with focusing properties that enable localised spectroscopic measurements. Micro-beads based, multiplexed fluorescence detection is performed with the AWG + CCD system and the results have demonstrated capabilities of using the adapted AWG device for localised, multiplexed fluorescence detections, opening up potential applications in the field of cell sorting and single cell analysis. Furthermore, the AWG-microfluidic device is investigated for absorption spectroscopy measurement. As a test system, the pH dependence of the absorption spectra of bromophenol blue is measured to illustrate how an AWG device could be used as a colorimetric pH sensor. Overall, it is believed that the AWG technology holds great potential to realise a compact, integrated spectroscopic biosensor for point-of-care applications