This Project is aimed at developing rare earth ion doped chalcogenide glasses targeting mid-infrared (MIR) fibre lasers, emitting in the wavelength region 4 - 5 μm. The work reported in this thesis has two objectives: (i) a study of the Ge-As-In-Se glass system when doped with a single species of rare earth (RE) ions, i.e. praseodymium (Pr3+) or cerium (Ce3+), or when co-doped with two rare earth ion species: Pr3+ and Ce3+, and (ii) a study of the effect of replacing a gallium (Ga) additive with an indium (In) additive on the physical and optical properties of the undoped and Pr3+ doped Ge-As-(Ga/In)-Se glasses and fibres. The MIR, i.e. 3 - 25 μm wavelength, offers to advance many photonics areas including bio-medical imaging spectroscopy for human tissue sensing in vivo for early cancer diagnosis. Low loss RE-ion doped MIR fibre lasers are potential pumps for MIR supercontinuum generation (SCG) sources for a compact MIR broadband device. Also, MIR fibre narrowband lasers offer potential new wavelengths for laser medical surgery. To date, there are no MIR rare earth ion doped glass fibre lasers emitting at wavelengths ≥ 4 μm. Selenide (Se)-based glasses, a member of the chalcogenide glass family, are known for their wide transparency up to 12 μm and good rare earth ion solubility. In the Project, an additive to the Ge-As-Se glass system of indium or gallium is considered to help decluster the rare earth ions and increase their solubility in the as-prepared Pr3+ doped Ge-As-(Ga/In)-Se glasses. However, an indium additive is concluded here to achieve a lower rare earth ion solubility limit than that obtained using the equivalent gallium additive in the Ge-As-(Ga/In)-Se glass systems. On the other hand, the photoluminescent intensity is concluded here to be approximately doubled when using an indium additive in Pr3+ doped Ge-As-In- Se, compared to the analogous gallium glasses. Furthermore, the decay lifetime, at the same emission wavelength of 4.7 μm, is found to be longer in the Pr3+ doped Ge-As-In-Se glasses when compared to the Pr3+ doped Ge-As- Ga-Se glasses. Overall, for a singly-doped Ge-As-In-Se glass system, Pr3+ offer wide photoluminescence spectral emission in the range 3 - 6 μm, which promotes this type of glass fibre as an active source for MIR laser emission in the target range of 4 - 5 μm. However, the photoluminescent decay lifetime, at 4.7 μm, of Pr3+ doped Ge-As-In-Se is concluded to decrease substantially with the number of thermal processes invoked to fabricate the glass-based fibres; a lifetime of 7 - 9 ms measured on the as-prepared fibres is compared to the decay lifetime of 9 - 10.1 ms that were found in the bulk glasses. Alternatively, the addition of Ce3+ in the Ge-As-In-Se glass system is concluded to offer a larger absorption cross-section than that of the Pr3+ in the wavelength range 3.5 - 5 μm. Co-doping the Pr3+ / Ce3+ in Ge-As-In-Se in order to enhance the MIR photoluminescence emission in the range 3 - 6 μm is also investigated. It is concluded that rare earth ions, in particular Ce3+ and / or Pr3+, doped chalcogenide glass fibres based on the Ge-As-In-Se glass system, developed through this Project, are strong candidates towards achieving MIR fibre lasers.

The controlled emission and absorption of single photons is an important enabling technology in the fields of quantum communication, cryptography and computing. We have realised a novel single photon source, based on a miniature ‘endcap' ion trap with integrated optical fibres. To minimise distortion of the trapping field the fibres are tightly integrated and recessed within the two hollow cylindrical rf electrodes of the trap. This allows us to bring the fibres to within approximately 300 μm of the trapped ion. With the fibres in place we are able to collect the ion's fluorescence using no further optics. In this thesis the ion trap is fully characterised, and the quantum nature of the light demonstrated in the results of a variant on the Hanbury Brown-Twiss photon-correlation experiment. The scheme will ultimately be extended to implement a coherent ion-photon interface through strong coupling cavity-QED. Towards this end, an ultra-high-finesse cavity has been designed and fabricated by laser-machining and coating surfaces with a range of radii of curvature on the end facets of the fibres. To improve the stability and precision manipulation of the cavity in-vacuum, an entirely new trap has been designed and built. Finally, the current status of the fibre cavity and the outlook for the experiment are presented.

Ho kai Cheung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 112-114). / Ho Kai Cheung. / Acknowledgements --- p.i / Abstract --- p.ii / Contents --- p.iii / Chapter Chapter 1. --- Introduction --- p.1 / Chapter Chapter 2. --- QNM and Green's function --- p.6 / Chapter 2.1 --- Introduction to QNM --- p.7 / Chapter 2.2 --- QNM and Green's function --- p.9 / Chapter 2.3 --- Modes of the universe and Green's function --- p.11 / Chapter Chapter 3. --- Correlation function and Green's function --- p.16 / Chapter 3.1 --- Equation of motion approach --- p.17 / Chapter 3.2 --- NM approach --- p.20 / Chapter Chapter 4. --- Correlation function : QNM expansion --- p.23 / Chapter 4.1 --- QNM expansion of correlation function --- p.24 / Chapter 4.2 --- Physical Examples --- p.27 / Chapter 4.2.1 --- One dimensional laser cavity --- p.27 / Chapter 4.2.2 --- Dielectric slab --- p.40 / Chapter Chapter 5. --- Quantization of EM field : modes of the universe approach --- p.49 / Chapter 5.1 --- Spherical wave expansion --- p.49 / Chapter 5.2 --- Quantization of EM field --- p.52 / Chapter 5.3 --- Correlation function : NM expansion --- p.56 / Chapter Chapter 6. --- QNM expansion of EM correlation function I --- p.59 / Chapter 6.1 --- TE part result --- p.61 / Chapter 6.2 --- TM part result --- p.65 / Chapter Chapter 7. --- QNM expansion of EM correlation function II --- p.69 / Chapter 7.1 --- Dyadic Green's function --- p.69 / Chapter 7.2 --- Green's function and correlation function : EM case --- p.72 / Chapter 7.3 --- QNM expansion of correlation function --- p.73 / Chapter Chapter 8. --- Sum rules --- p.76 / Chapter 8.1 --- Proof of sum rules --- p.77 / Chapter 8.2 --- Equivalence of two approaches --- p.78 / Chapter 8.3 --- Discussion of the QNM expansion --- p.79 / Chapter Chapter 9. --- EM field fluctuation in dielectric sphere --- p.82 / Chapter 9.1 --- Modes of the universe approach (revision) --- p.83 / Chapter 9.2 --- QNM approach --- p.85 / Chapter 9.3 --- Increase convergence by sum rules --- p.90 / Chapter Chapter 10. --- Conclusion --- p.97 / Appendix A. Scalar Green's function by normalized NM --- p.100 / Appendix B. Modification of existence of QNM on imaginary axis --- p.102 / Appendix C. Tensor Tij --- p.104 / Appendix D. Evaluation of aW+(wn)/aw --- p.106 / Appendix E. Classical dyadic Green's function --- p.107 / Appendix F. QNM expansion of Tij inside a leaky cavity --- p.109 / Appendix G. Symmetric properties of Fij --- p.111 / Bibliography --- p.112

<p> This dissertation encompasses experimental and theoretical studies on two cornerstones of modern nonlinear optics: laser filamentation and harmonic generation. Laser filaments are self-guided light structures balanced by Kerr self-focusing and diffraction/plasma defocusing, enabling applications in lightning guiding, long-range spectroscopy, and high-precision laser weapons. Harmonic generation is a nonlinear process that up-converts optical frequencies, and it is a promising source of table-top, ultrashort X-ray/UV radiation. </p><p> The goal of this work is two-fold: control and visualization of nonlinear optical phenomena. First, variable focusing geometries are used to eliminate high-power laser multifilamentation, which is a stochastic process that is notoriously difficult to control. Next, two-color pump-probe experimental schemes are used to enhance third-harmonic generation in air by several orders of magnitude. Our experimental results agree well with calculations based on state-of-the-art unidirectional pulse propagation equations, which give insight into the physical mechanisms underlying our experimental findings. An overarching theme of this work is ultrafast visualization: by combining femtosecond-time-resolved pump-probe methods with advanced quantitative phase microscopy, we can visualize and quantitatively characterize dynamically-evolving micro-structures during various nonlinear laser-matter interactions. Finally, this work will describe some novel properties of mid-infrared and long-wavelength infrared ultrashort pulse propagation, with a focus on the generation of light bullets, which represent a holy grail of nonlinear optics.</p><p>

No description available.

Time-resolved magneto-optical imaging (TRMOI) technique allows dynamic ac transport measurements on superconductors. The high time and spatial resolutions of the measurements also offer good quantitative data analysis of the MO images. YBa2Cu 3O7-delta (YBCO) was discovered as a high-temperature superconductor (HTSC) which has wide applications due to its high critical temperature of Tc = 91 K, and high critical current density Jc in the order of 106-7 Acm-2. Many of the applications require high ac current load and a high magnetic field. We study the interaction behavior of YBCO thin films in an ac transport current and a dc magnetic field by the TRMOI technique.;In this dissertation, I first introduce the applications of high-temperature superconductors with focus on YBCO and describe the advantages of the TRMOI technique we developed over other methods to map the magnetic flux distribution of superconductors. The theories to understand the magnetic properties of HTSC are presented, followed by theoretical models. I also introduce a newly developed finite elemental method (FEM) simulation which is proved to be a better theoretical guideline to our data analysis. The TRMOI experimental setup and the procedures are discussed in detail. I show step-by-step the calibration of light intensity profiles averaged from MO images to determine magnetic field distribution, and a numerical inversion of the Biot-Savart law to calculate the current density distributions.;The current density evolution in YBCO thin films is studied by TRMOI as a function of the phase of an ac current applied simultaneously with a perpendicular dc magnetic field. The measurements show that an ac current enables the vortex matter in YBCO thin films to reorganize into two coexisting steady states of driven vortex motion with different characteristics. to study the transport current effects in YBCO thin films, we present a new empirical method to separate the total current distribution into a circulating shielding current and a transport current.;Furthermore, we performed TRMOI measurements on multifilamentary YBCO thin films with six superconducting filaments. Several sets of measurements with different experimental parameters are compared to find optimized measurements especially fitting the TRMOI technique for best quantitative results. The integrated transport current in the optimized measurements agrees fairly well with the current we applied. Nearly half of the transport current flows in the most outer two filaments while the rest of the current flows roughly evenly in the inner four filaments. Comparing with the FEM simulation results, the multifilamentary film shows higher critical current than the single bridged TBCO thin film Finger-like inhomogeneous flux penetration patterns are observed in the TRMOI study of YBCO coated conductors in ac current regime. A quantitative analysis of the images show how the grain boundary network affects the overall behavior of the flux and current density evolution.

Nonlinear optical (NLO) processes are optical phenomena involving a nonlinear response to an applied light field. Two kinds of nonlinearities are studied in this dissertation: magnetic-induced second-harmonic generation (MSHG) interacting with surface plasmon, called "nonlinear magnetoplasmonics" (NMP), and the nonlinear index induced by a strong pump beam in Titanium doped sapphire crystal, referred to as population-induced nonlinear index effect.;The fundamentals of the major effects involved are discussed, which include: surface plasmon and its field enhancement effect, MSHG technique and phenomenological calculations, the contrast ratio of magnetic switching, the calculation of lensing effects, population induced strain, and photoelastic effect. Furthermore, the experimental techniques and setup are presented. Two ultrafast laser systems and the design of a spatially and temporally homogenized chirped pulse amplifier are also elaborated, because these are the most important devices in the experiments.;In the study of population-induced nonlinear index effect, a fast measurement system is developed and one of the photoelastic constants of Ti:sapphire is obtained, which is useful to optimize Ti:sapphire lasers and amplifiers. In the study of NMP, the MSHG signal enhancement effect and the magnetic contrast tuning effect are discovered in a single crystal iron film. The two jump switching process induced by the cubic magnetic anisotropy of the iron film opens the way for simultaneously investigating both longitudinal and transverse magnetization components regardless of the external magnetic field. This study has potential usage in quaternary magnetic storage systems because it enables the read-out of all four magnetization states from crystalline iron with high contrast ratio, and it is also of interest for bio-chemical sensor applications due to its very high surface sensitivity and simple structure.

No description available.

archives@tulane.edu / In the past decades, the terahertz science and technology have been extensively studied due to their potential applications in fundamental physics, material characterization, communication, sensing and imaging. Although a lot terahertz optical devices have been proposed recently, but efficient, high-performance terahertz optical devices are still in great demand. With the development of plasmonic research and nano-/micro- fabrication techniques, plasmon and metasurface based terahertz optical devices demonstrate their capacity to fit these needs. It is crucial to learn the plasmon and metasurface mediated terahertz optical phenomena for designing such terahertz optical devices. This thesis will explore several plasmon and metasurface mediated terahertz optical phenomena and propose possible solutions for the design of terahertz optical devices. The plasmonic resonant responses of sub-wavelength metallic and dielectric gratings on Indium Antimonide (InSb) are first studied. The designed sub-wavelength metasurface structures are able to couple normal incident terahertz wave with the surface standing plasmon modes whose propagation constant is controlled by the period of the structure. The excited resonant mode on the metallic grating structure is sensitive to its ambient environment which could be potentially applied in molecular sensing. The high-refractive index dielectric grating on InSb wafer enables us to intentionally tune the plasmonic response of the structure which offers more flexibility for terahertz devices. The non-reciprocal reflection and reciprocal transmission of InSb wafer under weak external magnetic field is reported then. The surface plasmon theory of this non-reciprocal reflection and reciprocal transmission is reviewed and confirmed by the experiments. A high-performance THz optical isolator is then proposed based on this non-reciprocal reflection. A novel experiments setup to measure the quadratic terahertz nonlinearities using second-harmonic lock-in detection is proposed. The experimental method is demonstrated by measuring the THz Kerr effect on (110) Gallium Phosphide (GaP) crystal. The experimental design is extended to measure the second-harmonic generation of non-centrosymmetric media. We also design a split-ring-resonator (SRR) metasurface to enhance the second-harmonic generation from non-centrosymmetric media. / 1 / SHUAI LIN

In emission spectral measurement with a dispersive spectrometer, if the entrance slit is widely opened, more light from a relatively large sample area can be collected, thus both energy throughput and spatial averaging advantages can be achieved in the measurement. With the entrance slit widely opened, the spectral bandpass becomes large. Radiations of different wavelengths likely fall on the same area of the detector. This can lead to a multiplex advantage and also extend the accessible wavelength range for a given spectral window. / The problem for opening the entrance slit is the decrease of spectral resolution. This project aimed to overcome this problem so that all the advantages associated with opening entrance slit are retained without loss of spectral resolution. The research we have done to solve this problem is to apply Hadamard transform and deconvolution in spectral measurements. The way we implement Hadamard transform in emission spectroscopy is to take spectra with a Hadamard mask in place of the conventional entrance slit, then inversely transform the measured data to recover the well-resolved spectra with improved signal-to-noise ratio. A spectrum can also be taken simply with the entrance slit widely opened. By deconvolving the slit function with such a wide-slit spectrum a best resolved spectrum can be recovered. Major difficulties involving in deconvolution have been discussed in Chapter 5 of this dissertation, and a novel algorithm is proposed there as well. Another important aspect involved in this project is the incorporation of fiber optics with Hadamard transform and deconvolution in spectral measurements. This greatly improved the flexibility and collection efficiency in our measurement system. / Source: Dissertation Abstracts International, Volume: 52-10, Section: B, page: 5236. / Major Professor: Charles K. Mann. / Thesis (Ph.D.)--The Florida State University, 1991.