Optics and Quantum Electronics

Contains table of contents for Section 3 and reports on twenty research projects.Charles S. Draper Laboratories Contract DL-H-467138Joint Services Electronics Program Contract DAAL03-92-C-0001Joint Services Electronics Program Grant DAAH04-95-1-0038U.S. Air Force - Office of Scientific Research Contract F49620-91-C-0091MIT Lincoln LaboratoryNational Science Foundation Grant ECS 90-12787Fujitsu LaboratoriesNational Center for Integrated PhotonicsHoneywell Technology CenterU.S. Navy - Office of Naval Research (MFEL) Contract N00014-94-1-0717U.S. Navy - Office of Naval Research (MFEL) Grant N00014-91-J-1956National Institutes of Health Grant NIH-5-R01-GM35459-09U.S. Air Force - Office of Scientific Research Grant F49620-93-1-0301MIT Lincoln Laboratory Contract BX-5098Electric Power Research Institute Contract RP3170-25ENEC

Technologies for single chip integrated optical gyroscopes

Optical gyroscopes are being employed for navigational purposes for decades now and have achieved comparable or better reliability and performance than rotor-based gyroscopes. Mechanical gyros are however generally bulky, heavy and consume more power which make them unsuitable for miniaturized applications such as cube satellites and drones etc. Therefore, much effort is being expended worldwide to fabricate optical gyros having tactical grade robustness and reliability, small size, weight, cost and power consumption with minimal sacrifice of sensitivity. Integrated optics is an obvious approach to achieving this. This work comprises detailed comparative analysis of different types and structures of integrated optical gyroscopes to find out the suitable option for applications which require a resolution of <10 o/h. Based on the numerical analysis, Add-drop ring resonator-based gyro is found to be a suitable structure for integration which has a predicted shot noise limited resolution of 27 o/h and 2.71 o/h for propagation losses of 0.1 dB/cm and 0.01 dB/cm respectively. An integrated gyro is composed of several optical components which include a laser, 3dB couplers, phase/frequency modulators, sensing cavity and photodetectors. This requires hybrid integration of multiple materials technologies and so choices about which component should be implemented in which technology. This project also undertakes theoretical optimization of few of the above-mentioned optical components in materials systems that might offer the most convenient/tolerant option, this including 3dB coupler, thermo-optic phase modulator and sensing cavity (resonator and waveguide loop). In particular, the sensing element requires very low propagation loss waveguides which can best be realised from Si3N4 or Ta2O5. The optimised Si3N4 or Ta2O5 waveguides however are not optimal for other functions and this is shown and alternatives explored where the Si3N4 or Ta2O5 can easily be co-integrated. The fabrication process of low loss Si3N4 and Ta2O5 waveguides are also reported in this thesis. Si3N4 films were grown by using low pressure chemical vapor deposition (LPCVD) technique. Dry etching of Si3N4 films have been optimized to produce smooth and vertical sidewalls. Experimental results predicted that the propagation loss of 0.009 dB/cm is achievable by using optimum waveguide dimensions and silica cladding with the relatively standard processes available within the Laser Physics Centre at the Australian National University. A CMOS back end of line compatible method was developed to deposit good quality Ta2O5 films and silica claddings through ion beam sputtering (IBS) method. Plasma etching of Ta2O5 waveguides has been demonstrated by using a gas combination of CHF3/SF6/Ar/O2. Oxygen was introduced into the chamber to produce non-vertical sidewalls, so the waveguides could be cladded without voids with IBS silica. Average propagation losses of 0.17 dB/cm were achieved from Ta2O5 waveguides which appeared after extensive investigation to be limited by the spatial inhomogeneity of the processing. Lastly, a detailed theoretical and experimental analysis was performed to find out the possible causes of the higher average propagation loss in Ta2O5 waveguides, some sections being observed with 0.02 dB/cm or lower losses

Fibre interferometry for differential measurements

This thesis investigates the use of interferometry as an interrogation technology for the measurement of differential length at two widely separate locations. Differential length measurements are essential and can have many applications in industrial processes, therefore accurate measurements can be a critical. Such differential length measurements can be applied to aspects of differential pressure. Using an all optical fibre approach, the research utilises the effects of light interference for both low coherent and high coherent light sources for the determination of a differential length between individual sensing cavities separated by up to 10’s of meters. The construction of the differential length interrogation system makes use of two Fabry-Perot cavities arranged in a tandem configuration, as a means of determining the differential length between them. Such an arrangement provides a common path through which an optical broadband light source at a central wavelength of 1550 nm can propagate. As a consequence of this configuration, differential lengths are made simply using one single measurement, removing the need to determine each individual length. An additional benefit of this common optical path prevents environmental factors such as temperature and air pressures from affecting the measurement length in question. Using a scanning reference Michelson interferometer to induce an optical path change, low coherence interference effects are present when the optical path length of the differential Fabry-Perot cavities is equal to the optical path length difference in the Michelson interferometer. Using a separate DFB laser light source to illuminate the reference interferometer high coherence interference fringes, present when the optical path length of one interferometer arm is changing due to a piezo fibre stretcher, can be analysed to provide an accurate length determination. Taking into consideration the noise within the system the interrogation technique has a length measurement resolution of 27.43 nm. Demonstrations show that a differential length of 82.539 μm could be measured with an uncertainty of 41.00 nm. Through the characterisation of a deformable silicon diaphragm, it would be possible to construct a sensing system capable of measuring a differential pressure of 1 Pa in 100 kPa. This however would require a 9.13 mm thick diaphragm, with a radius of 0.35 m. Such a diaphragm would be out of the question and so further investigation into reducing the length measurement resolution would need to be carried out

Optics in Our Time

Optics, Lasers, Photonics, Optical Devices; Quantum Optics; Popular Science in Physics; History and Philosophical Foundations of Physic

Optoelectronics – Devices and Applications

Optoelectronics - Devices and Applications is the second part of an edited anthology on the multifaced areas of optoelectronics by a selected group of authors including promising novices to experts in the field. Photonics and optoelectronics are making an impact multiple times as the semiconductor revolution made on the quality of our life. In telecommunication, entertainment devices, computational techniques, clean energy harvesting, medical instrumentation, materials and device characterization and scores of other areas of R&D the science of optics and electronics get coupled by fine technology advances to make incredibly large strides. The technology of light has advanced to a stage where disciplines sans boundaries are finding it indispensable. New design concepts are fast emerging and being tested and applications developed in an unimaginable pace and speed. The wide spectrum of topics related to optoelectronics and photonics presented here is sure to make this collection of essays extremely useful to students and other stake holders in the field such as researchers and device designers

Photonic Vector Processing Techniques for Radiofrequency Signals

[EN] The processing of radiofrequency signals using photonics means is a discipline that appeared almost at the same time as the laser and the optical fibre. Photonics offers the capability of managing broadband radiofrequency (RF) signals thanks to its low transmission attenuation, a variety of linear and non-linear phenomena and, recently, the potential to implement integrated photonic subsystems. These features open the door for the implementation of multiple functionalities including optical transportation, up and down frequency conversion, optical RF filtering, signal multiplexing, de-multiplexing, routing and switching, optical sampling, tone generation, delay control, beamforming and photonic generation of digital modulations, and even a combination of several of these functionalities. This thesis is focused on the application of vector processing in the optical domain to radiofrequency signals in two fields of application: optical beamforming, and photonic vector modulation and demodulation of digital quadrature amplitude modulations. The photonic vector control enables to adjust the amplitude and phase of the radiofrequency signals in the optical domain, which is the fundamental processing that is required in different applications such as beamforming networks for direct radiating array (DRA) antennas and multilevel quadrature modulation. The work described in this thesis include different techniques for implementing a photonic version of beamforming networks for direct radiating arrays (DRA) known as optical beamforming networks (OBFN), with the objectives of providing a precise control in terrestrial applications of broadband signals at very high frequencies above 40 GHz in communication antennas, optimizing the size and mass when compared with the electrical counterparts in space application, and presenting new photonic-based OBFN functionalities. Thus, two families of OBFNs are studied: fibre-based true time delay architectures and integrated networks. The first allow the control of broadband signals using dispersive optical fibres with wavelength division multiplexing techniques and advanced functionalities such as direction of arrival estimation in receiving architectures. In the second, passive OBFNs based on monolithically-integrated Optical Butler Matrices are studied, including an ultra-compact solution using optical heterodyne techniques in silicon-on-insulator (SOI) material, and an alternative implementing a homodyne counterpart in germanium doped silica material. In this thesis, the application of photonic vector processing to the generation of quadrature digital modulations has also been investigated. Multilevel modulations are based on encoding digital information in discrete states of phase and amplitude of an electrical signal to enhance spectral efficiency, as for instance, in quadrature modulation. The signal process required for generating and demodulating this kind of signals involves vector processing (phase and amplitude control) and frequency conversion. Unlike the common electronic or digital implementation, in this thesis, different photonic based signal processing techniques are studied to produce digital modulation (photonic vector modulation, PVM) and demodulation (PVdM). These techniques are of particular interest in the case of broadband signals where the data rate required to be managed is in the order of gigabit per second, for applications like wireless backhauling of metro optical networks (known as fibre-to-the-air). The techniques described use optical dispersion in optical fibres, wavelength division multiplexing and photonic up/down conversion. Additionally, an optical heterodyne solution implemented monolithically in a photonic integrated circuit (PIC) is also described.[ES] El procesamiento de señales de radiofrecuencia (RF) utilizando medios fotónicos es una disciplina que apareció casi al mismo tiempo que el láser y la fibra óptica. La fotónica ofrece la capacidad de manipular señales de radiofrecuencia de banda ancha, una baja atenuación, procesados basados en una amplia variedad de fenómenos lineales y no lineales y, recientemente, el potencial para implementar subsistemas fotónicos integrados. Estas características ofrecen un gran potencial para la implementación de múltiples funcionalidades incluyendo transporte óptico, conversión de frecuencia, filtrado óptico de RF, multiplexación y demultiplexación de señales, encaminamiento y conmutación, muestreo óptico, generación de tonos, líneas de retardo, conformación de haz en agrupaciones de antenas o generación fotónica de modulaciones digitales, e incluso una combinación de varias de estas funcionalidades. Esta tesis se centra en la aplicación del procesamiento vectorial en el dominio óptico de señales de radiofrecuencia en dos campos de aplicación: la conformación óptica de haces y la modulación y demodulación vectorial fotónica de señales digitales en cuadratura. El control fotónico vectorial permite manipular la amplitud y fase de las señales de radiofrecuencia en el dominio óptico, que es el procesamiento fundamental que se requiere en diferentes aplicaciones tales como las redes de conformación de haces para agrupaciones de antenas y en la modulación en cuadratura. El trabajo descrito en esta tesis incluye diferentes técnicas para implementar una versión fotónica de las redes de conformación de haces de en agrupaciones de antenas, conocidas como redes ópticas de conformación de haces (OBFN). Se estudian dos familias de redes: arquitecturas de retardo en fibra óptica y arquitecturas integradas. Las primeras permiten el control de señales de banda ancha utilizando fibras ópticas dispersivas con técnicas de multiplexado por división de longitud de onda y funcionalidades avanzadas tales como la estimación del ángulo de llegada de la señal en la antena receptora. En la segunda, se estudian redes de conformación pasivas basadas en Matrices de Butler ópticas integradas, incluyendo una solución ultra-compacta utilizando técnicas ópticas heterodinas en silicio sobre aislante (SOI), y una alternativa homodina en sílice dopado con germanio. En esta tesis, también se han investigado técnicas de procesado vectorial fotónico para la generación de modulaciones digitales en cuadratura. Las modulaciones multinivel codifican la información digital en estados discretos de fase y amplitud de una señal eléctrica para aumentar su eficiencia espectral, como por ejemplo la modulación en cuadratura. El procesado necesario para generar y demodular este tipo de señales implica el procesamiento vectorial (control de amplitud y fase) y la conversión de frecuencia. A diferencia de la implementación electrónica o digital convencional, en esta tesis se estudian diferentes técnicas de procesado fotónico tanto para la generación de modulaciones digitales (modulación vectorial fotónica, PVM) como para su demodulación (PVdM). Esto es de particular interés en el caso de señales de banda ancha, donde la velocidad de datos requerida es del orden de gigabits por segundo, para aplicaciones como backhaul inalámbrico de redes ópticas metropolitanas (conocida como fibra hasta el aire). Las técnicas descritas se basan en explotar la dispersión cromática de la fibra óptica, la multiplexación por división de longitud de onda y la conversión en frecuencia. Además, se presenta una solución heterodina implementada monolíticamente en un circuito integrado fotónico (PIC).[CA] El processament de senyals de radiofreqüència (RF) utilitzant mitjans fotònics és una disciplina que va aparèixer gairebé al mateix temps que el làser i la fibra òptica. La fotònica ofereix la capacitat de manipular senyals de radiofreqüència de banda ampla, una baixa atenuació, processats basats en una àmplia varietat de fenòmens lineals i no lineals i, recentment, el potencial per implementar subsistemes fotònics integrats. Aquestes característiques ofereixen un gran potencial per a la implementació de múltiples funcionalitats incloent transport òptic, conversió de freqüència, filtrat òptic de RF, multiplexació i demultiplexació de senyals, encaminament i commutació, mostreig òptic, generació de tons, línies de retard, conformació de feix en agrupacions d'antenes i la generació fotònica de modulacions digitals, i fins i tot una combinació de diverses d'aquestes funcionalitats. Aquesta tesi es centra en l'aplicació del processament vectorial en el domini òptic de senyals de radiofreqüència en dos camps d'aplicació: la conformació òptica de feixos i la modulació i demodulació vectorial fotònica de senyals digitals en quadratura. El control fotònic vectorial permet manipular l'amplitud i la fase dels senyals de radiofreqüència en el domini òptic, que és el processament fonamental que es requereix en diferents aplicacions com ara les xarxes de conformació de feixos per agrupacions d'antenes i en modulació multinivell. El treball descrit en aquesta tesi inclou diferents tècniques per implementar una versió fotònica de les xarxes de conformació de feixos en agrupacions d'antenes, conegudes com a xarxes òptiques de conformació de feixos (OBFN), amb els objectius de proporcionar un control precís en aplicacions terrestres de senyals de banda ampla a freqüències molt altes per sobre de 40 GHz en antenes de comunicacions, optimitzant la mida i el pes quan es compara amb els homòlegs elèctrics en aplicacions espacials, i la presentació de noves funcionalitats fotòniques per agrupacions d'antenes. Per tant, s'estudien dues famílies de OBFNs: arquitectures de retard en fibra òptica i arquitectures integrades. Les primeres permeten el control de senyals de banda ampla utilitzant fibres òptiques dispersives amb tècniques de multiplexació per divisió en longitud d'ona i funcionalitats avançades com ara l'estimació de l'angle d'arribada del senyal a l'antena receptora. A la segona, s'estudien xarxes de conformació passives basades en Matrius de Butler òptiques en fotònica integrada, incloent una solució ultra-compacta utilitzant tècniques òptiques heterodinas en silici sobre aïllant (SOI), i una alternativa homodina en sílice dopat amb germani. D'altra banda, també s'ha investigat en aquesta tesi tècniques de processament vectorial fotònic per a la generació de modulacions digitals en quadratura. Les modulacions multinivell codifiquen la informació digital en estats discrets de fase i amplitud d'un senyal elèctric per augmentar la seva eficiència espectral, com ara la modulació en quadratura. El processat necessari per generar i desmodular aquest tipus de senyals implica el processament vectorial (control d'amplitud i fase) i la conversió de freqüència. A diferència de la implementació electrònica o digital convencional, en aquesta tesi s'estudien diferents tècniques de processament fotònic tant per a la generació de modulacions digitals (modulació vectorial fotònica, PVM) com per la seva demodulació (PVdM). Això és de particular interès en el cas de senyals de banda ampla, on la velocitat de dades requerida és de l'ordre de gigabits per segon, per a aplicacions com backhaul sense fils de xarxes òptiques metropolitanes (coneguda com fibra fins l'aire). Les tècniques descrites es basen en explotar la dispersió cromàtica de la fibra òptica, la multiplexació per divisió en longitud d'ona i la conversió en freqüència. A més, es presePiqueras Ruipérez, MÁ. (2016). Photonic Vector Processing Techniques for Radiofrequency Signals [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/63264TESI

Continuous Wave and Pulsed Erbium-Doped Fiber Lasers for Microwave Photonics Applications

El objetivo de esta tesis es el diseño, fabricación y caracterización de láseres de fibra como fuentes ópticas compactas con aplicaciones de fotónica de microondas, como son la generación de ondas en la banda de microondas-milimétricas y la conversión analógico-digital asistida ópitcamente. Las prestaciones de la tecnología electrónica en estas aplicaciones están limitadas para frecuencias de trabajo de decenas de GHZ. En este contexto, la tecnología óptica ha encontrado aplicaciones potenciales con el fin de extender las especificaciones de sistemas de microondas tradicionales. En particular, los láseres de de fibra se presentan como fuentes ópticas fiables de coste reducido las cuales están ganando interés como soluciones compactas en comparación con láseres de estado sólido. Esta tesis presenta el desarrrollo de un láser de fibra de realimentación distribuida capaz de emitir en dos longitudes de onda en régimen continuo para la generación de señales de microondas por fotomezclado. La cavidad óptica está constituida por una red de difracción de Bragg grabada en una fibra dopada con erbio, en la que se aplican dos desfases puntuales. La sintonización dinámica de la diferencia de frecuencia de los dos modos emitidos se lleva a cabo mediante el empleo de dos actuadores piezoeléctricos controlados por una fuente de tensión continua. Tras la fotodetección de la salida del láser se obtiene una señal de microondas con un rango de sintonización continuo de 0.12-7 GHz. La máxima frecuencia de sintonización viene limitada por el ancho de banda espectral de la red de difracción. Por ello, se ha estudiado una segunda configuración del láser con el fin de incrementar el rango de sintonización. La implementación de dos cavidades de realimentación distribuida con diferentes frecuencias de emisión en la misma fibra dopada permite un control más versátil de las frecuencias de emisión de ambos modos ópticos. Esta fuente altamente compacta y sencilla es capaz de proporcionar unVillanueva Ibáñez, GE. (2012). Continuous Wave and Pulsed Erbium-Doped Fiber Lasers for Microwave Photonics Applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17801Palanci

Stimulated Brillouin Scattering in Integrated Circuits: Platforms and Applications

Coherent interactions between light and sound have been of significant interest since the invention of the laser. Stimulated Brillouin scattering (SBS) is a type of coherent interaction where light is scattered from optically generated acoustic waves. SBS is a powerful tool for optical and microwave signal processing, with applications ranging from telecommunications and Radar, to spatial sensing and microscopy. Over the last decade there has been increasing interest in the investigation of Brillouin scattering at device scales smaller than the wavelength of light. New interactions with the waveguide boundaries in these systems are capable of altering the strength of SBS, from complete suppression to orders of magnitude increases. The landmark demonstration of Brillouin scattering in planar waveguides, just six years ago, represents a new frontier for this field. This work explores the effective generation and harnessing of stimulated Brillouin scattering within modern photonic circuits. After establishing the foundations of linear and nonlinear optical circuits, we investigate the Brillouin processes available in multimode waveguides. We experimentally demonstrate giant Brillouin amplification using spiral waveguides consisting of soft-glass materials. We then integrate this soft-glass onto the standard platform for photonic circuits, silicon on insulator, without any reduction in performance. We apply these advanced devices to the field of microwave photonics and create high suppression microwave filters with functionality far beyond traditional electronic circuits. This thesis is a significant step towards Brillouin enabled integrated photonic processors

Photodetectors for graphene-based integrated photonics

The development of integrated optical circuits has enabled a diverse portfolio of chipscale photonic applications—ranging from data communication over sensing to imaging—that is set to grow further as new device concepts in, for example, quantum information processing and optical neural networks mature. While silicon photonics has emerged as a viable candidate to translate proof-of-principle demonstrations to mass-manufacturing, the fabrication of photonic integrated circuits (PICs) and their subcomponents remains highly heterogeneous, which drives up cost and slows down progress towards faster and more power-efficient performance. In this dissertation, I demonstrate how single-layer graphene (SLG) can bring active functionality to arbitrary passive waveguide platforms, offering a more universal approach to developing integrated photonic components. SLG can be transferred to PICs without the limitations or complexity of traditional deposition or bonding processes. It also stands to outperform conventional semiconductors in terms of speed and spectral operating range due to its ultra-fast carrier dynamics, high carrier mobility, and gapless bandstructure. Using the key component for optical-to-electrical signal conversion—the photodetector—as an example, here I demonstrate graphene-based components on three different PIC platforms. First, I show plasmonic enhanced graphene photodetectors (GPDs) on silicon nitride waveguides, which generate a voltage from optically generated hot-carrier distributions in SLG via the photo-thermoelectric (PTE) effect. Then, I demonstrate PTE-GPDs—fabricated from layered material heterostructures—on a silicon-on-insulator microring resonator. Both detectors operate at Telecom wavelengths (λ = 1.55 μm), are compatible with high-speed (> 10 GHz) operations, and hold the current records in voltage responsivity—R ∼ 12 V/W and R ∼ 90 V/W—for waveguide-integrated GPDs fabricated from chemical vapour deposited and mechanically exfoliated SLG, respectively. I then go on to show how established GPD concepts can be translated to an integrated mid-infrared (λ = 3.8 μm) platform based on sub-wavelength grating waveguides in silicon and study how light-graphene interaction under in-plane incidence can be further optimised to improve GPD performance. Finally, I develop new approaches towards high-quality, scalable SLG on PICs, critically required to advance graphene-based integrated photonics towards industrial production