Photonic integrated circuit | EPFL Graph Search

A photonic integrated circuit (PIC) or integrated optical circuit is a microchip containing two or more photonic components which form a functioning circuit. This technology detects, generates, transports, and processes light. Photonic integrated circuits utilize photons (or particles of light) as opposed to electrons that are utilized by electronic integrated circuits. The major difference between the two is that a photonic integrated circuit provides functions for information signals imposed on optical wavelengths typically in the visible spectrum or near infrared (850–1650 nm). The most commercially utilized material platform for photonic integrated circuits is indium phosphide (InP), which allows for the integration of various optically active and passive functions on the same chip. Initial examples of photonic integrated circuits were simple 2-section distributed Bragg reflector (DBR) lasers, consisting of two independently controlled device sections – a gain section and a

Light Confinement and Nonlinear Light-Matter Interaction in Semiconductor Photonic Crystal Cavities

Mohamed Sabry Abdel-Aliem Mohamed

The ability to control and manipulate light is a fundamental aspect that is at the very core of the development of integrated photonic circuits. It is desirable to achieve such control down to a scale that is comparable to or smaller than the wavelength of light, to enable highly efficient interaction with matter, which can eventually go down to single photon levels. Photonic crystals are particularly appealing in that respect, by providing optical bandgaps and facilitating dispersion shaping, through the precise patterning of layers. This is to be accomplished ideally in compact designs that are well-suited for fabrication with current technology and by utilizing material that has the capacity for integration. By exploiting existing light-matter interaction mechanisms, the available toolset for component design can be expanded, allowing to build optical chips with a wide range of functionality. In the current work, a platform for integrated III-nitride photonic components on silicon is designed and implemented. A refined fabrication process for III-nitride micro- and nanostructures is developed, leading to the realization of suspended optical devices with both high performance and structural stability. Thorough optical and material characterization of the semiconductor layers is conducted to identify potential limitations, particularly with epitaxial GaN on Si technology, with respect to current crystal growth techniques. AlN layers based on a sputter-deposition process are proposed as an alternative for passive optical devices. Two-dimensional photonic crystals are designed in gallium nitride and aluminum nitride, targeting operational wavelengths in the near-infrared telecom range. Optimized photonic crystal cavities are considered for maximizing light confinement in the semiconductor layers. By utilizing resonance enhancement, second and third harmonic generation are demonstrated in gallium nitride photonic crystal cavities featuring record-high quality factor values. This is achieved through a far-field coupling approach under low-power continuous-wave operation. High conversion efficiencies are attained in gallium nitride, exceeding previous demonstrations in the material. Propagation of the harmonic signals in the semiconductor layer is analyzed using finite-element time-domain modeling for the feasibility of an extraction mechanism. Moreover, slow light coupled cavity waveguides are developed in a silicon platform, relying on optimized cavity designs that feature wideband operation in the near-infrared telecom range. A record-high value for group-index bandwidth product is achieved in the devices through improved design implementation. An end-fire based Fourier-space imaging technique is applied for the characterization of the optical structures, through which spatially-selective reconstruction of dispersion maps enabled accurate extraction of slow light properties. The influence of finite-size effects on slow light behavior is elucidated by implementing extended cavity chains. Furthermore, light transport regimes across the dispersion band are identified including the transition towards diffusive light transport and subsequent localization. The performance of coupled-cavity waveguides in the presence of disorder is quantified, revealing constraints on slow light transport, considering state-of-the-art fabrication.

EPFL2018

Advanced Diamond Microfabrication for Microoptics and Photonics

Marcell Kristof Kiss

Diamond is an exceptional material - hard, stiff, transparent, which makes it ideal for the fabrication of optical and mechanical systems that take advantage of these properties. Diamond is not only "better", but it offers the possibility of integrating bright colour centres. These optically active defects can be exploited for a variety of applications, including the study of fundamental science, magnetometry, biosensing and new types of lasers. Despite the attractive properties of diamond for optics, no standard platform exists to create photonic circuits and devices. This thesis shows the realisation of a diamond-on-insulator photonics platform, that aims to combine the versatility of the silicon-on-insulator photonics with the capability of performing diamond science in single crystal guided-wave devices. The diamond-on-insulator substrate is achieved via ion implantation-based cut of a single crystal membrane and bonding of the membrane to an insulator layer. This approach provides a monolithic fabrication process that scales to commercial exploitation, bringing convenient access to the study of diamond light-matter interactions without requiring custom substrate fabrication. Furthermore, the possibility of releasing the diamond devices adds access to freestanding structures, opening the way to diamond micro-opto-electro-mechanical systems and optomechanics. Diamond also makes an excellent microoptics substrate, due to its high laser damage threshold, transparency and high refractive index, which is an attractive combination for high-power, compact optical systems operating in the UV, visible and near-infrared. Different diamond etching techniques are developed and investigated in this thesis, that enable the realisation of unique features. These techniques are employed to create diamond diffractive microoptical components, which are then characterised, showing high-quality surfaces that closely match the designed features, indicating reliable fabrication and resulting in excellent optical performance. These devices have applications in high power beamsplitters, beam shapers and compact spectrometers.

EPFL2019

Accordabilité de la réponse optique des cristaux photoniques par infiltration de matériaux organiques

Pascale El-Kallassi

Photonic crystals are stuctures in which the refractive index varies periodically on the wavelength scale in one, two or three dimensions. Due to interference effects, these structures can forbid light propagation over a large spectral range called "the photonic bandgap". Integrated optics is one of the potential applications of photonic crystals in which the information can be treated as a light signal that propagates through photonic crystal-based devices, such as filters, lasers, waveguides, bends and multiplexers. The photonic crystals structures studied for integrated optics applications consist of periodic arrays of holes etched through classical semiconducteur-based planar waveguides. For any practical application, the optical properties of the fabricated components have to be tuned by external means. In this thesis, we explore a possible approach to photonic crystal tuning : the infiltration of photoactive organic materials in the holes of these photonic structures. First we considered liquid crystals, which exhibit anisotropic optical properties like birefringence due to their long-range orientational order. This latter molecular organization can be modified by external factors, i.e. temperature and electric field. Nematic liquid crystals were infiltrated in the holes of the photonic crystals to tune their properties by changing the temperature and applying an electric field. Moreover, the organization of liquid crystals in the nanometric holes were studied by optical techniques. The demand for all-optical tunable devices in integrated optical circuits led us to consider the possibility of optically tuning the response of photonic crystal structures. For this purpose, we used photo-induced phase transitions of a liquid crystal blend doped with azobenzene photochromic molecules. Since the phase transitions in these mixtures depend on the concentration of the photochromic compound and on the temperature, we studied in detail the phase diagram of the blend. The last part of this thesis focused on one of the most innovative aspects in the domain of photonic crystal tuning : selective infiltration to locally modify the optical properties of the photonic structures. We used the photopolymerization of acrylate monomers by ultraviolet laser irradiation. Finally, with three clear examples, this thesis shows that organic photoactive materials are well-adapted to be combined with photonic crystals. We demonstrated that the obtained hybrid structures are very promising for integrated optics applications.

EPFL2009