Joris Roels

Bio: Joris Roels is an academic researcher from Ghent University. The author has contributed to research in topics: Silicon on insulator & Phosphine. The author has an hindex of 12, co-authored 40 publications receiving 1009 citations.

Optomechanical device actuation through the optical gradient force

Abstract: Optical forces are widely used to manipulate microparticles such as living cells, DNA and bacteria. The forces used in these 'optical tweezers' originate from the strongly varying electromagnetic field in the focus of a high-power laser beam. This field gradient polarizes the particle, causing the positively and negatively charged sides of the dipole to experience slightly different forces. It was recently realized that the strong field gradient in the near-field of guided wave structures can also be exploited for actuating optomechanical devices, and initial theoretical work in this area was followed rapidly by several experimental demonstrations. This Review summarizes the rapid development in this field. First, the origin of the optical gradient force is discussed in detail. Several experimental demonstrations and approaches for enhancing the strength of the effect are then discussed. Finally, some of the possible applications of the effect are reviewed.

Tunable optical forces between nanophotonic waveguides

Abstract: The optical-gradient force between two nanophotonic waveguides can be tuned from attractive to repulsive by controlling the relative phase of the optical fields injected into the waveguides.

Ultracompact Phase Modulator Based on a Cascade of NEMS-Operated Slot Waveguides Fabricated in Silicon-on-Insulator

Abstract: Phase modulation is one of the key functionalities in an integrated photonics circuit. In the silicon photonics platform, several approaches have been undertaken. The thermooptic effect is slow and relatively power hungry, whereas a carrier-based approach is fast ( >; Gb/s) but lossy and weak. Integration of other (e.g., electrooptic) materials typically struggles with fabrication issues that limit the effect. Here, we present a nanoelectromechanical systems-based approach. By applying a voltage over a freestanding slot waveguide, the slot width will change, resulting in an effective index change and thus a phase change. Using a cascaded structure, the effect can be enlarged without reducing the speed. A phase change of 40° was observed for a voltage of 13 V over a cascade of three 5.8-μm-long freestanding slots. The expected speed is in the MHz range.

Silicon microring resonators

Abstract: An overview is presented of the current state-of-the-art in silicon nanophotonic ring resonators. Basic theory of ring resonators is discussed, and applied to the peculiarities of submicron silicon photonic wire waveguides: the small dimensions and tight bend radii, sensitivity to perturbations and the boundary conditions of the fabrication processes. Theory is compared to quantitative measurements. Finally, several of the more promising applications of silicon ring resonators are discussed: filters and optical delay lines, label-free biosensors, and active rings for efficient modulators and even light sources.

Hydrogen Sensors - A review

Abstract: Hydrogen sensors are of increasing importance in connection with the development and expanded use of hydrogen gas as an energy carrier and as a chemical reactant. There are an immense number of sensors reported in the literature for hydrogen detection and in this work these sensors are classified into eight different operating principles. Characteristic performance parameters of these sensor types, such as measuring range, sensitivity, selectivity and response time are reviewed and the latest technology developments are reported. Testing and validation of sensor performance are described in relation to standardisation and use in potentially explosive atmospheres so as to identify the requirements on hydrogen sensors for practical applications.

Electromagnetically induced transparency and slow light with optomechanics

Abstract: Controlling the interaction between localized optical and mechanical excitations has recently become possible following advances in micro- and nanofabrication techniques. So far, most experimental studies of optomechanics have focused on measurement and control of the mechanical subsystem through its interaction with optics, and have led to the experimental demonstration of dynamical back-action cooling and optical rigidity of the mechanical system. Conversely, the optical response of these systems is also modified in the presence of mechanical interactions, leading to effects such as electromagnetically induced transparency (EIT) and parametric normal-mode splitting. In atomic systems, studies of slow and stopped light (applicable to modern optical networks and future quantum networks) have thrust EIT to the forefront of experimental study during the past two decades. Here we demonstrate EIT and tunable optical delays in a nanoscale optomechanical crystal, using the optomechanical nonlinearity to control the velocity of light by way of engineered photon-phonon interactions. Our device is fabricated by simply etching holes into a thin film of silicon. At low temperature (8.7 kelvin), we report an optically tunable delay of 50 nanoseconds with near-unity optical transparency, and superluminal light with a 1.4 microsecond signal advance. These results, while indicating significant progress towards an integrated quantum optomechanical memory, are also relevant to classical signal processing applications. Measurements at room temperature in the analogous regime of electromagnetically induced absorption show the utility of these chip-scale optomechanical systems for optical buffering, amplification, and filtering of microwave-over-optical signals.

Nanoscaled metal borides and phosphides: recent developments and perspectives

Abstract: and Perspectives Sophie Carenco,†,‡,§,∥,⊥ David Portehault,*,†,‡,§ Ced́ric Boissier̀e,†,‡,§ Nicolas Meźailles, and Cleḿent Sanchez*,†,‡,§ †Chimie de la Matier̀e Condenseé de Paris, UPMC Univ Paris 06, UMR 7574, Colleg̀e de France, 11 Place Marcelin Berthelot, 75231 Paris Cedex 05, France ‡Chimie de la Matier̀e Condenseé de Paris, CNRS, UMR 77574, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Chimie de la Matier̀e Condenseé de Paris, Colleg̀e de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05, France Laboratory Heteroelements and Coordination, Chemistry Department, Ecole Polytechnique, CNRS-UMR 7653, Palaiseau, France