Integrated Optic Interferometric Sensor

An improved integrated optic interferometric sensor uses a planar waveguide to offer detection sensitivity equal to the Mach-Zehnder interferometric sensor, while retaining the input coupling and manufacturing ease characteristic of a planar waveguide. Enhanced output signal processing capabilities are provided by use of at least two integrated optic interferometric sensors employing planar constructs.Georgia Tech Research Corporatio

Acousto-optic interaction in seimiconductor multi-layer optical waveguides for device applications.

This thesis reports on work undertaken over the last three years on the modelling of the physical processes relevant to acousto-optic diffraction in multi-layered, single and multiple quantum well (QW) structures, and is mainly concerned with the AlGaAs/GaAs material system. The propagation of surface acoustic waves (SAWs) on top of a general multi-layer structure is modelled using a basis of orthonormal polynomials to represent the appropriate solutions. The guided optical mode profiles are then determined through Maxwell's equations and matching of optical fields and field gradients at layer interfaces. The acousto-optic diffraction efficiency as a function of the wavelength of the SAW is calculated from the framework of coupled mode theory and the effects of compositional variations to the structure are considered. The effect of the SAWs on the electron/hole energy eigenvalues and envelope functions in QW structures is then considered in more detail, using a simple static approximation for the SAW. The change in complex refractive index of the QW structures is then calculated using the results of a density matrix theory expressed within the context of a semi-classical approach. Results show that multi-layer structures have distinct advantages over single layer structures for acousto-optic applications in terms of the added control available over both the SAW induced field quantities and the guided optical mode profiles. In addition, the possibilities for constructing multiple quantum well (MQW) structures within the multi-layer structure will lead to enhanced changes in refractive index due to the presence of a SAW induced electric field. It is shown that these refractive index changes are significantly larger than those possible in bulk materials for the same acoustic powers. Also, the results indicate that the non-linearity of the SAW induced fields will, for high enough acoustic frequencies, produce different SAW induced electric fields within adjacent quantum wells of the MQW structure, an effect not suggested previously when such devices have been proposed

Integrated optics technology study

The status and near term potential of materials and processes available for the fabrication of single mode integrated electro-optical components are discussed. Issues discussed are host material and orientation, waveguide formation, optical loss mechanisms, wavelength selection, polarization effects and control, laser to integrated optics coupling fiber optic waveguides to integrated optics coupling, sources, and detectors. Recommendations of the best materials, technology, and processes for fabrication of integrated optical components for communications and fiber gyro applications are given

Feasibility study of an integrated optic switching center

The design of a high data rate switching center for a satellite tracking station is discussed. The feasibility of a switching network using an integrated switching matrix is assessed. The preferred integrated optical switching scheme was found to be an electro-optic Bragg diffraction switch. To ascertain the advantages of the integrated optics switching center, its properties are compared to those of opto-electronic and to electronics switching networks

Guided Wave Optics

Phenomena associated with the propagation and manipulation of light in thin-film dielectric waveguides are presently the object of considerable research effort, directed toward possible applications in communications and information processing. The theory of dielectric waveguide modes is reviewed, and the topics of directional coupling, input-output coupling, modulation, and distributed feedback laser sources are treated on the basis of coupled-mode theory. A summary of experimental results for each of the guided-wave optical phenomena covered by the theory is also presented

Electrically-Controlled Suppression of Rayleigh Backscattering in an Integrated Photonic Circuit

Undesirable light scattering is an important fundamental cause for photon loss in nanophotonics. Rayleigh backscattering can be particularly difficult to avoid in wave-guiding systems and arises from both material defects and geometric defects at the subwavelength scale. It has been previously shown that systems with broken time-reversal symmetry (TRS) can naturally suppress detrimental Rayleigh backscattering, but these approaches have never been demonstrated in integrated photonics or through practical TRS-breaking techniques. In this work, we show that it is possible to suppress disorder-induced Rayleigh backscattering in integrated photonics via electrical excitation, even when defects are clearly present. Our experiment is performed in a lithium niobate on insulator (LNOI) integrated ring resonator at telecom wavelength, in which TRS is strongly broken through an acousto-optic interaction that is induced via radiofrequency input. We present evidence that Rayleigh backscattering in the resonator is almost completely suppressed by measuring both the optical density of states and through direct measurements of the back-scattered light. We additionally provide an intuitive argument to show that, in an appropriate frame of reference, the suppression of backscattering can be readily understood as a form of topological protection

Dispersion tailoring in both integrated photonics and fiber-optic based devices

Tesis por compendio[EN] This Thesis focuses on the study, implementation and characterization of chromatic dispersion tailoring employing both optical fiber and photonic integrated waveguides. Chromatic dispersion causes that the different spectral components of an optical pulse travel at different velocities. This effect can be separated into two different fundamental contributions, material dispersion and waveguide dispersion. Chromatic dispersion can be tailored through the design of the structural parameters of the device in order to obtain specific characteristics in the resulting dispersion profile such as low values of dispersion and/or zero dispersion at a desired wavelength, for example. This approach is very useful in dispersion-dependent applications. In this PhD, we investigate chromatic dispersion tailoring in two different transmission mediums, photonic integrated waveguides and optical fiber. In the first case, two different geometries of Silicon-on-Insulator (SOI) integrated waveguides, strip and slot, are considered. By varying structural parameters such as the cross-section, aspect ratio or fill factor, different chromatic dispersion profiles are obtained. In addition, the influence of the slot location is evaluated. This study is carried out using simulation software in order to obtain the effective refractive index profile as a function of wavelength, which is later differentiated to obtain the final dispersion values. Besides, chromatic dispersion in both waveguide geometries is experimentally measured using an interferometer technique. In the second case, the chromatic dispersion present in a tapered fiber is studied. A tapered fiber consists of a narrow waist located between two transition regions and it allows the modification of the conventional propagation conditions due to the interference between the modes propagating through the waist. This interference between modes creates a transmission pattern which depends on the waist length and the effective refractive indexes of the modes travelling through the waist. By applying stress to the tapered fiber its interference pattern can be modified. Chromatic dispersion profile of tapered fibers is obtained, tailored and compared with the dispersion profile of conventional single-mode fibers.[ES] Esta Tesis se centra en el estudio, implementación y caracterización del control de la dispersión cromática empleando tanto fibra óptica como guías integradas fotónicas. La dispersión cromática provoca que las distintas componentes espectrales asociadas con el pulso óptico viajen a diferentes velocidades. Este efecto puede ser dividido en sus dos contribuciones fundamentales, la dispersión del material y la dispersión de la guía. La dispersión cromática puede ser controlada a través del diseño de los parámetros estructurales del dispositivo para poder obtener así determinadas características en el perfil de dispersión resultante como por ejemplo bajos valores o localización de la longitud de onda de dispersión cero en una longitud de onda deseada. Este método es muy útil en aplicaciones dependientes de la dispersión. En esta Tesis, investigamos el control de la dispersión cromática en dos medios de transmisión diferentes, las guías fotónicas integradas y la fibra óptica. En el primer caso, se consideran dos geometrías diferentes de guías integradas en silicio, las guías convencionales y las guías ranuradas. Mediante la modificación de los parámetros estructurales como la sección transversal de la guía, su relación de aspecto o el factor de llenado, se obtienen diferentes perfiles de dispersión cromática. Además, se evalúa la influencia de la situación de la ranura. Mediante software de simulación, se obtiene el perfil de índice de refracción efectivo en función de la longitud de onda, que posteriormente se deriva y se obtiene el valor de la dispersión. Asimismo, se mide experimentalmente la dispersión en ambas geometrías utilizando una técnica interferométrica. En el segundo caso, se analiza la dispersión cromática que presenta una fibra de tipo taper. Esta geometría consiste en una cintura estrecha situada entre dos regiones de transición y permite la modificación de las condiciones de propagación convencionales debido a la interferencia entre los modos que se propagan por la cintura, que crea un patrón de transmisión dependiente de la longitud de la cintura y de los índices efectivos de los modos. Aplicando tensión sobre la fibra, su patrón de interferencia puede ser modificado. La dispersión cromática de las fibras taper se obtiene, se modifica y se compara con el perfil de dispersión de una fibra convencional.[CA] La tesi a exposar se centra en l'estudi, implementació i caracterització del control de la dispersió cromàtica empleant la fibra òptica i les guies integrades fotòniques. La dispersió cromàtica provoca que els distints components espectrals associats amb la pols òptica viatgen a diferents velocitats. Aquest pot dividir-se en les dos contribucions fonamentals corresponents: la dispersió del material i la dispersió de la guia. La dispersió cromàtica pot controlar-se a través del disseny dels paràmetres estructurals del dispositiu per poder obtindre aixi determinades característiques en el perfil de dispersió resultant, com per exemple, baixos valors o localizació de la longitud d'ona de dispersió zero a una longitud d'ona desitjada. No obstant això, aquest mètode és molt útil en aplicacions depenents de la dispersió. A més a més, investiguem el control de dispersió cromàtica en dos mitjans de transmissió diferents, les guies fotòniques integrades i la fibra òptica. D'una banda, es consideren dos geometries diferents de guies integrades en silici, les guies convencionals i les ranurades. Mitjançant la modificació dels paràmetres estructurals com la secció transversal de la guia, la relació d'apecte o el factor d'ompliment, obtenim diferents perfils de dispersió cromàtica. Fins i tot, s'avalua la influència de la situació de la ranura. Mitjançant el programari de simulació, obtenim el perfil d'índex de refracció efectiu en funció de la longitud d'ona, que posteriorment es derivarà i s'obrindrà el valor de la dispersió. Tanmateix, es mesura experimentalment la dispersió en les dos geometries utilitzant una tècnica interferomètrica. D'altra banda, analitzam la dispersió cromàtica que presenta una fibra de tipus taper. Aquesta consisteix en una cintura estreta situada entre dos regions de transició que, ens permet la modificació de les condicions de propagació convencional com a causa d'una interferència entre els modes que es propaguen per la cintura i els índex efectius dels modes. Si apliquem tensió sobre la fibra, el seu patró d'interferència podria ser modificat. La dispersió d'una fibra cromàtica de les fibres taper s'obté, es modific i es compara amb el perfil de dispersió d'una fibra convencional.Mas Gómez, SM. (2015). Dispersion tailoring in both integrated photonics and fiber-optic based devices [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/54113TESISCompendi