Staff directory Guillermo Arregui Bravo

Guillermo Arregui Bravo

Doctoral Student
Phononic and Photonic Nanostructures



  • All-optical radio-frequency modulation of Anderson-localized modes

    Arregui G., Navarro-Urrios D., Kehagias N., Torres C.M.S., García P.D. Physical Review B; 98 (18, 180202) 2018. 10.1103/PhysRevB.98.180202. IF: 3.813

    All-optical modulation of light relies on exploiting intrinsic material nonlinearities [V. R. Almeida, Nature 431, 1081 (2004)NATUAS0028-083610.1038/nature02921]. However, this optical control is rather challenging due to the weak dependence of the refractive index and absorption coefficients on the concentration of free carriers in standard semiconductors [R. A. Soref and B. R. Bennett, Proc. SPIE 704, 32 (1987)PSISDG0277-786X10.1117/12.937193]. To overcome this limitation, resonant structures with high spatial and spectral confinement are carefully designed to enhance the stored electromagnetic energy, thereby requiring lower excitation power to achieve significant nonlinear effects [K. Nozaki, Nat. Photonics 4, 477 (2010)1749-488510.1038/nphoton.2010.89]. Small mode-volume and high-quality (Q)-factor cavities also offer an efficient coherent control of the light field and the targeted optical properties. Here, we report on optical resonances reaching Q∼105 induced by disorder on photonic/phononic-crystal waveguides. At relatively low excitation powers (below 1mW), these cavities exhibit nonlinear effects leading to periodic (up to ∼35 MHz) oscillations of their resonant wavelength. Our system represents a test bed to study the interplay between structural complexity and material nonlinearities and their impact on localization phenomena and introduces a different functionality to the toolset of disordered photonics. © 2018 American Physical Society.

  • Optical modulation of coherent phonon emission in optomechanical cavities

    Maire J., Arregui G., Capuj N.E., Colombano M.F., Griol A., Martinez A., Sotomayor-Torres C.M., Navarro-Urrios D. APL Photonics; 3 (12, 126102) 2018. 10.1063/1.5040061.

    Optomechanical (OM) structures are well suited to study photon-phonon interactions, and they also turn out to be potential building blocks for phononic circuits and quantum computing. In phononic circuits, in which information is carried and processed by phonons, OM structures could be used as interfaces to photons and electrons thanks to their excellent coupling efficiency. Among the components required for phononic circuits, such structures could be used to create coherent phonon sources and detectors, but more complex functions remain challenging. Here, we propose and demonstrate a way to modulate the coherent phonon emission from OM crystals by a photothermal effect induced by an external laser, effectively creating a phonon switch working at ambient conditions of pressure and temperature and the working speed of which is only limited by the build-up time of the mechanical motion of the OM structure. We additionally demonstrate two other modulation schemes: modulation of harmonics in which the mechanical mode remains active but different harmonics of the optical force are used, and modulation to and from a chaotic regime. Furthermore, due to the local nature of the photothermal effect used here, we expect this method to allow us to selectively modulate the emission of any single cavity on a chip without affecting its surroundings in the absence of mechanical coupling between the structures, which is an important step toward freely controllable networks of OM phonon emitters. © 2018 Author(s).


  • Optomechanical coupling in the Anderson-localization regime

    García P.D., Bericat-Vadell R., Arregui G., Navarro-Urrios D., Colombano M., Alzina F., Sotomayor-Torres C.M. Physical Review B; 95 (11, 115129) 2017. 10.1103/PhysRevB.95.115129. IF: 3.836

    Optomechanical crystals, purposely designed and fabricated semiconductor nanostructures, are used to enhance the coupling between the electromagnetic field and the mechanical vibrations of matter at the nanoscale. However, in real optomechanical crystals, imperfections open extra channels where the transfer of energy is lost, reducing the optomechanical coupling efficiency. Here, we quantify the role of disorder in a paradigmatic one-dimensional optomechanical crystal with full phononic and photonic band gaps. We show how disorder can be exploited as a resource to enhance the optomechanical coupling beyond engineered structures, thus providing a new tool set for optomechanics. © 2017 American Physical Society.