R. Houdré

École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland

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Publications (347)581.56 Total impact

  • Mario Tonin · Nicolas Descharmes · Romuald Houdré
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    ABSTRACT: We demonstrate the fabrication of a hybrid PDMS/glass microfluidic layer that can be placed on top of non-transparent samples and allows high-resolution optical microscopy through it. The layer mimics a glass coverslip to limit optical aberrations and can be applied on the sample without the use of permanent bonding. The bonding strength can withstand to hold up to 7 bars of injected pressure in the channel without leaking or breaking. We show that this process is compatible with multilayer soft lithography for the implementation of flexible valves. The benefits of this application is illustrated by optically trapping sub-wavelength particles and manipulate them around photonic nano-structures. Among others, we achieve close to diffraction limited imaging through the microfluidic assembly, full control on the flow with no dynamical deformations of the membrane and a 20-fold improvement on the stiffness of the trap at equivalent trapping power.
    No preview · Article · Jan 2016 · Lab on a Chip
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    ABSTRACT: We demonstrate the use of photonic crystal cavities in order to optically trap submicron-sized objects. The resonant nature of the trap provides different capabilities compared to classical optical tweezers. We study the Brownian motion of trapped particles with back focal plane interferometry.
    No preview · Article · Apr 2015

  • No preview · Article · Nov 2014 · Nature Communications
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    ABSTRACT: The design of photonic crystal cavities has always presented a considerable challenge over the past two decades. In this work, a global optimization technique has been used to maximize the Q / V ratio of a simple H0 type nanocavity. The optimization is carried out by allowing for shifts of several neighbouring holes along the x-and y-axes. The objective function of the evolutionary optimization was the cavity Q-factor, while reasonable restrictions were imposed on the magnitudes of the shifts in order to limit the variations in modal volume. The fabricated devices were coupled using a side-coupled scheme involving a photonic crystal W1 waveguide and the Q-factors measured. A maximum value of 418'000 was measured along with a modal volume (computed) of 0.34(λ/n)3 enabling an extremely high Q /V ratio of 1.2 million, which has also resulted in the onset of nonlinear optical effects including optical bistability at μW input powers.
    No preview · Conference Paper · Jul 2014
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    ABSTRACT: We fabricate and experimentally characterize an H0 photonic crystal slab nanocavity with a design optimized for maximal quality factor, Q = 1.7 x 10(6). The cavity, fabricated from a silicon slab, has a resonant mode at lambda = 1.59 mu m and a measured Q-factor of 400 000. It displays nonlinear effects, including high-contrast optical bistability, at a threshold power among the lowest ever reported for a silicon device. With a theoretical modal volume as small as V = 0.34(lambda/n)(3), this cavity ranks among those with the highest Q/V ratios ever demonstrated, while having a small footprint suited for integration in photonic circuits. (C) 2014 AIP Publishing LLC.
    No preview · Article · Jan 2014
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    ABSTRACT: We analyze and compare the effect of fabrication disorder on the quality factor of six well-known high-index photonic crystal cavity designs. The theoretical quality factors for the different nominal structures span more than three orders of magnitude, ranging from 5.4 × 10<sup>4</sup> to 7.5 × 10<sup>7</sup>, and the defect responsible for confining light is introduced in a different way for each structure. Nevertheless, among the different designs we observe similar behavior of the statistics of the disorder-induced light losses. In particular, we show that for high enough disorder, such that the quality factor is mainly determined by the disorder-induced losses, the measured quality factors differ marginally - not only on average as commonly acknowledged, but also in their full statistical distributions. This notably shows that optimizing the theoretical quality factor brings little practical improvement if its value is already much larger than what is typically measured, and if this is the case, there is no way to choose an alternative design more robust to disorder.
    No preview · Article · Nov 2013 · Optics Express
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    ABSTRACT: Photonic crystal (PhC) nanocavities are promising building blocks of future integrated photonic circuits. Owing to the high ratio between quality factor (Q) and modal volume (V), they can greatly enhance optical nonlinearities and radiation-matter interaction, establishing a new paradigm in cavity quantum electrodynamics. However, only few specific designs have reached measured Q-factors exceeding one million, mostly as a result of a heuristic optimization. Here, we develop a global optimization procedure based on an evolutionary algorithm that, if applied to simple moderate-Q nanocavities, can enhance their measured quality factor by over one decade, approaching the one-million range. In particular, we optimize and experimentally characterize a H0 PhC nanocavity, demonstrating a measured Q-factor reaching 418,000 combined with a modal volume $V=0.35(\lambda/n)^3$. This cavity ranks among those with the highest Q/V ratios ever demonstrated, while being spatially much more compact than ultrahigh-Q designs and thus optimal for integration in photonic circuits. It displays nonlinear effects in the microwatt power range, including high-contrast optical bistability at record-low threshold power in silicon. We highlight the versatility of the optimization procedure by further devising an alternate H0 design with a smaller modal volume of $V=0.26(\lambda/n)^3$ and a measured Q-factor of 260,000
    Preview · Article · Nov 2013 · Applied Physics Letters
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    ABSTRACT: Compact semiconductor light sources with high performance continuous-wave (CW) and single mode operation are highly demanded for many applications in the terahertz (THz) frequency range. Distributed feedback (DFB) and photonic crystal (PhC) quantum cascade (QC) lasers are amongst the leading candidates in this field. Absorbing boundary condition is a commonly used method to control the optical performance of a laser in double-metal confinement. However, this approach increases the total loss in the device and results in a large threshold current density, limiting the CW maximum output power and operating temperature. In this letter, a robust surface emitting continuous-wave terahertz QC laser is realized in a two-dimensional PhC structure by a second order Bragg grating extractor that simultaneously provides the boundary condition necessary for mode selection. This results in a 3.12 THz single mode CW operation with a 3 mW output power and a maximum operation temperature (Tmax) of 100 K. Also, a highly collimated far-field pattern is demonstrated, which is an important step towards real world applications.
    Full-text · Article · Sep 2013 · Laser & Photonics Review
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    ABSTRACT: We demonstrate a resonant optical trapping mechanism based on two-dimensional hollow photonic crystal cavities. This approach benefits simultaneously from the resonant nature and unprecedented field overlap with the trapped specimen. The photonic crystal structures are implemented in a 30 mm × 12 mm optofluidic chip consisting of a patterned silicon substrate and an ultrathin microfluidic membrane for particle injection and control. Firstly, we demonstrate permanent trapping of single 250 and 500 nm-sized particles with sub-mW powers. Secondly, the particle induces a large resonance shift of the cavity mode amounting up to several linewidths. This shift is exploited to detect the presence of a particle within the trap and to retrieve information on the trapped particle. The individual addressability of multiple cavities on a single photonic crystal device is also demonstrated.
    No preview · Article · Jun 2013 · Lab on a Chip
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    ABSTRACT: Exciton-polaritons are composite bosons (exciton-photon mixtures) in semiconductor microcavities. Relying on their strong interactions, we have demonstrated quantum optical effects in the microcavity emission, as well as quantum fluid properties in the polariton propagation.
    No preview · Conference Paper · Jun 2013
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    ABSTRACT: Exciton-polaritons are composite bosons (exciton-photon mixtures) in semiconductor microcavities. Relying on their strong interactions, we have demonstrated quantum optical effects in the microcavity emission, as well as quantum fluid properties in the polariton propagation.
    No preview · Conference Paper · Jun 2013
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    ABSTRACT: Surface emitting semiconductor lasers in the terahertz frequency range are highly demanded for spectroscopy, imaging, security and other applications. Due to their compactness and high power, Quantum Cascade Lasers (QCLs) are one of the most important laser sources in this region. The selection rule of intersubband transitions forces the radiation to be TM polarized and thus generated in-plane, consequently photonic structures have to be developed to extract the light vertically. Few approaches for surface emitting QCLs demonstrated the lasing of a second-order Bragg metallic grating patterned on top of a ridge or a surface emitting photonic crystal (PhC). PhC band-edge lasers with improved performance compared to Fabry-Perot lasers have already been reported. In this work a surface emitting band edge 2D PhC QCL is presented, using a second-order Bragg grating as a boundary condition. We show single mode devices operating around 3.1 THz with a maximum operating temperature of 125 K in pulsed operation, 100 K in CW, a farfield divergence of less than 20° or up to 12 mW of peak output power.
    No preview · Conference Paper · May 2013
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    ABSTRACT: We report on the first experimental demonstration of a resonant optical trap in a two-dimensional hollow photonic crystal cavity. Resonant trapping is implemented in an optofluidic silicon chip. Individual 250 and 500 nm polystyrene particles are trapped using optical powers of the order of 100 μW. Local refractive index perturbation associated with the particle presence lead to modifications of the cavity eigenfrequency. Back-action phenomena resulting from these perturbations are investigated. In particular, the existence of two distinct trapping regimes is demonstrated.
    No preview · Conference Paper · May 2013
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    ABSTRACT: Although optical technology provides the best solution for the transmission of information, all-optical devices must satisfy several qualitative criteria to be used as logic elements. In particular, cascadability is difficult to obtain in optical systems, and it is assured only if the output of one stage is in the correct form to drive the input of the next stage. Exciton-polaritons, which are composite particles resulting from the strong coupling between excitons and photons, have recently demonstrated huge non-linearities and unique propagation properties. Here we show that polariton fluids moving in the plane of the microcavity can operate as input and output of an all-optical transistor, obtaining up to 19 times amplification and demonstrating the cascadability of the system. Moreover, the operation as an AND/OR gate is shown, validating the connectivity of multiple transistors in the microcavity plane and opening the way to the implementation of polariton integrated circuits.
    No preview · Article · Apr 2013 · Nature Communications
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    ABSTRACT: We show a technique that images the intensity distribution and local state of polarization of the optical field of high-quality factor optical modes confined in dielectric planar photonic crystal nanocavities. Based on energy-loss spectroscopy of swift electrons, the technique gives a spatial resolution improved by a factor of 30 compared to the optical diffraction limit. Moreover, because the energy loss is induced by coupling of the moving charges with the local density of states of the dielectric cavity, it is sensitive to the entire volume of the confined electric field, not just its evanescent contributions. This three-dimensional sensitivity paves the way for a highly resolved tomography of confined modes in dielectric photonic nanostructures.
    No preview · Article · Apr 2013 · Physical review. B, Condensed matter
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    ABSTRACT: The optomechanical coupling between a resonant optical field and a nanoparticle through trapping forces is demonstrated. Resonant optical trapping, when achieved in a hollow photonic crystal cavity is accompanied by cavity backaction effects that result from two mechanisms. First, the effect of the particle on the resonant field is measured as a shift in the cavity eigenfrequency. Second, the effect of the resonant field on the particle is shown as a wavelength-dependent trapping strength. The existence of two distinct trapping regimes, intrinsically particle specific, is also revealed. Long optical trapping (>10 min) of 500 nm dielectric particles is achieved with very low intracavity powers (<120 μW).
    No preview · Article · Mar 2013 · Physical Review Letters
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    ABSTRACT: We report on GaN self-supported photonic structures consisting in freestanding waveguides coupled to photonic crystal waveguides and cavities operating in the near-infrared. GaN layers were grown on Si (111) by metal organic vapor phase epitaxy. E-beam lithography and dry etching techniques were employed to pattern the GaN layer and undercut the substrate. The combination of low-absorption in the infrared range and improved etching profiles results in cavities with quality factors as high as ∼5400. The compatibility with standard Si technology should enable the development of low cost photonic devices for optical communications combining wide-bandgap III-nitride semiconductors and silicon.
    No preview · Article · Mar 2013 · Applied Physics Letters
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    ABSTRACT: The first experimental demonstration of resonant optical trapping of dielectric particles in a hollow photonic crystal cavity is reported. The existence of mutual interaction between the confined field and the particle is revealed.
    No preview · Article · Jan 2013
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    ABSTRACT: We report the design and optical characterization of fully suspended wire waveguides and photonic crystal (PhC) membranes fabricated on a gallium nitride layer grown on silicon substrate operating at 1.5 μm. W1-type PhC waveguides are coupled with suspended wires and are investigated using a standard end-fire setup. The experimental and theoretical dispersion properties of the propagating modes in the wires and photonic-crystal waveguides are shown. Modified L3 cavities with quality factors of up to 2200 and heterostructure cavities with quality factors of up to 5400 are experimentally demonstrated.
    No preview · Article · Nov 2012 · Optics Letters
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    ABSTRACT: Photonic crystal (PhC) devices owing to their strong confinement of electromagnetic energy are considered to be excellent candidates for on chip optical trapping of dielectric or biological particles in the nanometer range. In this work, we study and present hollow PhC cavities and characterize them for their trapping stiffness, trapping stability and variation of resonance wavelength due to the presence of various sized single particles in the cavity.
    No preview · Article · Jun 2012 · Optical and Quantum Electronics

Publication Stats

7k Citations
581.56 Total Impact Points


  • 1992-2014
    • École Polytechnique Fédérale de Lausanne
      • • Institute of Condensed Matter Physics
      • • Laboratory for Molecular Engineering of Optoelectronic Nanomaterials
      • • Institute of Theoretical Physics
      Lausanne, Vaud, Switzerland
    • Paul Scherrer Institut
      Филлиген, Aargau, Switzerland
  • 2010
    • Ecole polytechnique fédérale de Lausanne
      Lausanne, Vaud, Switzerland
  • 1991-2002
    • Eawag: Das Wasserforschungs-Institut des ETH-Bereichs
      Duebendorf, Zurich, Switzerland
  • 2000
    • University of Southampton
      • Department of Physics and Astronomy
      Southampton, England, United Kingdom
  • 1999-2000
    • Institut de Chimie de la matière condensée de Bordeaux
      Pessac, Aquitaine, France
    • University of Glasgow
      • Division of Electronics and Electrical Engineering
      Glasgow, SCT, United Kingdom
  • 1997
    • Ecole Normale Supérieure de Paris
      • Laboratoire Pierre Aigrain
      Lutetia Parisorum, Île-de-France, France
  • 1993
    • École Polytechnique
      Paliseau, Île-de-France, France