Shaping of light beams with photonic crystals : spatial filtering, beam collimation and focusing

The research developed in the framework of this PhD thesis is a theoretical, numerical and experimental study of light beam shaping (spatial filtering, beam collimation and focusing) in the visible frequency range using photonic crystal structures. Photonic crystals (PhCs) are materials with periodic, spatially modulated refractive index on the wavelength scale. They are primarily known for their chromatic dispersion properties. However, they can also modify the spatial dispersion, which allows managing the spatial properties of the monochromatic light beams. In the first part of my thesis we experimentally show that particular spatial dispersion modification in PhCs can lead to spatial (angular) filtering of light beams. The study is focused on the spatial filtering efficiency improvement by introducing chirp (the variation of longitudinal period of the structure) in the crystal structure. Additionally, to enhance the effect, we consider different geometries and materials. The work presented in this PhD thesis brings closer to reality the creation of a new generation spatial filters for micro-photonic circuits and micro-devices. The second part of the study is devoted to the theoretical, numerical and experimental analysis of the formation of negative spatial dispersion in PhCs, which gives rise to collimation and focusing effects behind the PhCs. The ideas developed in my PhD also work in lossy systems, in particular in metallic PhCs. The simulation results for metallic PhCs are presented, in which both effects- spatial filtering and beam focusing, are shown.La recerca desenvolupada en el marc d'aquesta tesi doctoral és un estudi teòric, numèric i experimental de la modificació de la forma de feixos de llum (filtratge espacial, col·limació i focalització) en el rang visible de freqüències utilitzant estructures de cristall fotònic. Els cristalls fotònics (CFs) són materials amb una modulació periòdica de l'índex de refracció en l'escala de la longitud d'ona, i són principalment coneguts per les seves propietats relacionades amb la dispersió temporal. Tot i això, la dispersió espacial també pot ser modificada mitjançant CFs, fet que permet controlar les propietats espacials de feixos monocromàtics de llum. En la primera part de la tesi, mostrem experimentalment el fet que certes modificacions de la dispersió espacial en CFs poden donar lloc a filtratge espacial (angular) de feixos de llum. L'estudi es focalitza en la millora de l'eficiència del filtratge espacial mitjançant la introducció de "chirp" (la variació del període longitudinal de l'estructura) en el CF. A més, per tal d'incrementar l'efecte considerem diferents estructures i materials. El treball presentat en aquesta tesi doctoral acosta a la realitat la creació d'una nova generació de filtres espacials per a circuits micro-fotònics i micro-dispositius. La segona part d'aquest estudi se centra en l'anàlisi teòric, numèric i experimental de la formació de dispersió espacial negativa en CFs, la gual dóna lloc a efectes de col·limació i focalització un cop travessat el CF. Les idees desenvolupades en aquesta tesi doctoral també són aplicables a sistemes amb pèrdues, en particular a CFs metàl·lics. Els resultats de les simulacions mostren l'existència d'ambdós efectes, filtratge espacial i focalització, en CFs metàl·lics

Evidences of spatial (angular) filtering of sound beams by sonic crystals

We report experimental evidences of spatial (angular) filtering of sound beams propagating through sonic crystals. We show that at specific frequencies of the incident wave the paraxial plane wave compo- nents of the beam can be efficiently transmitted through the crystal, whereas the components propagat- ing at large angles are strongly reflected or deflected (filtered out) by the crystal. The modification of the angular field distribution results in formation of sound beams of relatively high spatial quality.The work was financieall supported by Spanish Ministry of since and Innovation and European Union FEDER through projects FIS2011-29731-C02-01 and -02, Generalitat Valenciana through the procect GV/2011/2055 and the UPV through PAID-05-12.Picó Vila, R.; Pérez Arjona, I.; Sánchez Morcillo, VJ.; Staliünas, K. (2013). Evidences of spatial (angular) filtering of sound beams by sonic crystals. Applied Acoustics. 74(7):945-948. https://doi.org/10.1016/j.apacoust.2013.01.003S94594874

High-Directional Wave Propagation in Periodic Gain/Loss Modulated Materials

Amplification/attenuation of light waves in artificial materials with a gain/loss modulation on the wavelength scale can be sensitive to the propagation direction. We give a numerical proof of the high anisotropy of the gain/loss in two dimensional periodic structures with square and rhombic lattice symmetry by solving the full set of Maxwell's equations using the finite difference time domain method. Anisotropy of amplification/attenuation leads to the narrowing of the angular spectrum of propagating radiation with wavevectors close to the edges of the first Brillouin Zone. The effect provides a novel and useful method to filter out high spatial harmonics from noisy beams

Enhanced sensing and conversion of ultrasonic Rayleigh waves by elastic metasurfaces

Recent years have heralded the introduction of metasurfaces that advantageously combine the vision of sub-wavelength wave manipulation, with the design, fabrication and size advantages associated with surface excitation. An important topic within metasurfaces is the tailored rainbow trapping and selective spatial frequency separation of electromagnetic and acoustic waves using graded metasurfaces. This frequency dependent trapping and spatial frequency segregation has implications for energy concentrators and associated energy harvesting, sensing and wave filtering techniques. Different demonstrations of acoustic and electromagnetic rainbow devices have been performed, however not for deep elastic substrates that support both shear and compressional waves, together with surface Rayleigh waves; these allow not only for Rayleigh wave rainbow effects to exist but also for mode conversion from surface into shear waves. Here we demonstrate experimentally not only elastic Rayleigh wave rainbow trapping, by taking advantage of a stop-band for surface waves, but also selective mode conversion of surface Rayleigh waves to shear waves. These experiments performed at ultrasonic frequencies, in the range of 400–600 kHz, are complemented by time domain numerical simulations. The metasurfaces we design are not limited to guided ultrasonic waves and are a general phenomenon in elastic waves that can be translated across scales

Enhanced transmission band in periodic media with loss modulation

Copyright (2014) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in: Applied Physics Letters 105, 204104 (2014); doi: 10.1063/1.4902387 and may be found at: http://dx.doi.org/10.1063/1.490238.We study the propagation of waves in a periodic array of absorbing layers. We report an anomalous increase of wave transmission through the structure related to a decrease of the absorption around the Bragg frequencies. The effect is first discussed in terms of a generic coupled wave model extended to include losses, and its predictions can be applied to different types of waves propagating in media with periodic modulation of the losses at the wavelength scale. The particular case of sound waves in an array of porous layers embedded in air is considered. An experiment designed to test the predictions demonstrates the existence of the enhanced transmission band. (C) 2014 AIP Publishing LLC.The work was supported by Spanish Ministry of Science and Innovation and European Union FEDER through Projects FIS2011-29731-C02-01 and -02, also MAT2009-09438. A.M.Y. would like to thank the Erasmus Mundus Project (WELCOME program) for supporting him. V.R.G. acknowledges financial support from the "Pays-de-la-Loire" through the post-doctoral program.Cebrecos Ruiz, A.; Picó Vila, R.; Romero García, V.; Yasser, AM.; Maigyte, L.; Herrero, R.; Botey, M.... (2014). Enhanced transmission band in periodic media with loss modulation. Applied Physics Letters. 105(20):204104-1-204104-4. doi:10.1063/1.4902387S204104-1204104-410520Figotin, A., & Vitebskiy, I. (2008). Absorption suppression in photonic crystals. Physical Review B, 77(10). doi:10.1103/physrevb.77.104421Figotin, A., & Vitebskiy, I. (2010). Magnetic Faraday rotation in lossy photonic structures. Waves in Random and Complex Media, 20(2), 298-318. doi:10.1080/17455030.2010.482575Erokhin, S. G., Lisyansky, A. A., Merzlikin, A. M., Vinogradov, A. P., & Granovsky, A. B. (2008). Photonic crystals built on contrast in attenuation. Physical Review B, 77(23). doi:10.1103/physrevb.77.233102Kumar, N., Botey, M., Herrero, R., Loiko, Y., & Staliunas, K. (2012). High-directional wave propagation in periodic loss modulated materials. Photonics and Nanostructures - Fundamentals and Applications, 10(4), 644-650. doi:10.1016/j.photonics.2012.06.003Staliunas, K., Herrero, R., & Vilaseca, R. (2009). Subdiffraction and spatial filtering due to periodic spatial modulation of the gain-loss profile. Physical Review A, 80(1). doi:10.1103/physreva.80.013821Kumar, N., Herrero, R., Botey, M., & Staliunas, K. (2013). Flat lensing by periodic loss-modulated materials. Journal of the Optical Society of America B, 30(10), 2684. doi:10.1364/josab.30.002684Psarobas, I. E. (2001). Viscoelastic response of sonic band-gap materials. Physical Review B, 64(1). doi:10.1103/physrevb.64.012303Lee, C.-Y., Leamy, M. J., & Nadler, J. H. (2010). Frequency band structure and absorption predictions for multi-periodic acoustic composites. Journal of Sound and Vibration, 329(10), 1809-1822. doi:10.1016/j.jsv.2009.11.030Laude, V., Escalante, J. M., & Martínez, A. (2013). Effect of loss on the dispersion relation of photonic and phononic crystals. Physical Review B, 88(22). doi:10.1103/physrevb.88.224302Hwan Oh, J., Jae Kim, Y., & Young Kim, Y. (2013). Wave attenuation and dissipation mechanisms in viscoelastic phononic crystals. Journal of Applied Physics, 113(10), 106101. doi:10.1063/1.4795285Hussein, M. I. (2009). Theory of damped Bloch waves in elastic media. Physical Review B, 80(21). doi:10.1103/physrevb.80.212301Andreassen, E., & Jensen, J. S. (2013). Analysis of Phononic Bandgap Structures With Dissipation. Journal of Vibration and Acoustics, 135(4). doi:10.1115/1.4023901Allard, J. F., & Atalla, N. (2009). Propagation of Sound in Porous Media. doi:10.1002/9780470747339Tournat, V., Pagneux, V., Lafarge, D., & Jaouen, L. (2004). Multiple scattering of acoustic waves and porous absorbing media. Physical Review E, 70(2). doi:10.1103/physreve.70.026609Umnova, O., Attenborough, K., & Linton, C. M. (2006). Effects of porous covering on sound attenuation by periodic arrays of cylinders. The Journal of the Acoustical Society of America, 119(1), 278-284. doi:10.1121/1.2133715Romero-García, V., Sánchez-Pérez, J. V., & Garcia-Raffi, L. M. (2010). Evanescent modes in sonic crystals: Complex dispersion relation and supercell approximation. Journal of Applied Physics, 108(4), 044907. doi:10.1063/1.3466988Christensen, J., Romero-García, V., Picó, R., Cebrecos, A., de Abajo, F. J. G., Mortensen, N. A., … Sánchez-Morcillo, V. J. (2014). Extraordinary absorption of sound in porous lamella-crystals. Scientific Reports, 4(1). doi:10.1038/srep04674Kogelnik, H., & Shank, C. V. (1972). Coupled‐Wave Theory of Distributed Feedback Lasers. Journal of Applied Physics, 43(5), 2327-2335. doi:10.1063/1.166149

Spatial Filter based on Photonic Crystals

Tesina realitzada en col.laboracio amb Institut de Ciències Fotòniques (ICFO), Universitat de Barcelona (UB) i Universitat Autònoma de Barcelona (UAB).Engish: Photonic crystals are considered as promising materials for controlling and manipulating the flow of light. In this work we give first experimental evidences of spatial filtering of light beams by three-dimensional ultra-low contrast Photonic crystals made in fused silica glass. Sequentially, we experimentally observe well collimated laser beam by a moderate contrast Photonic crystals of woodpile type. We interpret the observations by theoretical and numerical studies.Castellano: Los cristales fotónicos son considerados como materiales prometedores para el control y manipulación del flujo de luz. En este trabajo primero se muestran las evidencias del filtrado espacial de los rayos de luz mediante cristales fotónicos tridimensionales ultra-bajos hechos con vidrio fundido de sílica. Secuencialmente, hemos observado experimentalmente una buena colimaciñon del láser mediante cristales fotónicos de tipo pila. Se interpretan las observaciones tanto con estudios teóricos como estudios numéricos.Català: Els cristalls fotònics són considerats com a materials prometedors per controlar i manipular el fluxe de llum. En aquest treball donem primer les evidències experimentals del filtrat espacial dels rajos de llum mitjançant uns cristalls fotònics tridimensionals de contrast ultra-baix fets en vidre de sílica. Seqüencialment, hem observat experimentalment una bona col·limació del feix del làser per cristalls fotònics de contrast moderat del tipus pila. Interpretem les observacions tant amb estudis teòrics com numèrics

Spatial filtering with photonic crystals

Photonic crystals are well known for their celebrated photonic band-gaps-the forbidden frequency ranges, for which the light waves cannot propagate through the structure. The frequency (or chromatic) band-gaps of photonic crystals can be utilized for frequency filtering. In analogy to the chromatic band-gaps and the frequency filtering, the angular band-gaps and the angular (spatial) filtering are also possible in photonic crystals. In this article, we review the recent advances of the spatial filtering using the photonic crystals in different propagation regimes and for different geometries. We review the most evident configuration of filtering in Bragg regime (with the back-reflection-i.e., in the configuration with band-gaps) as well as in Laue regime (with forward deflection-i.e., in the configuration without band-gaps). We explore the spatial filtering in crystals with different symmetries, including axisymmetric crystals; we discuss the role of chirping, i.e., the dependence of the longitudinal period along the structure. We also review the experimental techniques to fabricate the photonic crystals and numerical techniques to explore the spatial filtering. Finally, we discuss several implementations of such filters for intracavity spatial filtering.Postprint (published version

Spatial Filter based on Photonic Crystals

Tesina realitzada en col.laboracio amb Institut de Ciències Fotòniques (ICFO), Universitat de Barcelona (UB) i Universitat Autònoma de Barcelona (UAB).Engish: Photonic crystals are considered as promising materials for controlling and manipulating the flow of light. In this work we give first experimental evidences of spatial filtering of light beams by three-dimensional ultra-low contrast Photonic crystals made in fused silica glass. Sequentially, we experimentally observe well collimated laser beam by a moderate contrast Photonic crystals of woodpile type. We interpret the observations by theoretical and numerical studies.Castellano: Los cristales fotónicos son considerados como materiales prometedores para el control y manipulación del flujo de luz. En este trabajo primero se muestran las evidencias del filtrado espacial de los rayos de luz mediante cristales fotónicos tridimensionales ultra-bajos hechos con vidrio fundido de sílica. Secuencialmente, hemos observado experimentalmente una buena colimaciñon del láser mediante cristales fotónicos de tipo pila. Se interpretan las observaciones tanto con estudios teóricos como estudios numéricos.Català: Els cristalls fotònics són considerats com a materials prometedors per controlar i manipular el fluxe de llum. En aquest treball donem primer les evidències experimentals del filtrat espacial dels rajos de llum mitjançant uns cristalls fotònics tridimensionals de contrast ultra-baix fets en vidre de sílica. Seqüencialment, hem observat experimentalment una bona col·limació del feix del làser per cristalls fotònics de contrast moderat del tipus pila. Interpretem les observacions tant amb estudis teòrics com numèrics

Spatial Filter based on Photonic Crystals

Tesina realitzada en col.laboracio amb Institut de Ciències Fotòniques (ICFO), Universitat de Barcelona (UB) i Universitat Autònoma de Barcelona (UAB).Engish: Photonic crystals are considered as promising materials for controlling and manipulating the flow of light. In this work we give first experimental evidences of spatial filtering of light beams by three-dimensional ultra-low contrast Photonic crystals made in fused silica glass. Sequentially, we experimentally observe well collimated laser beam by a moderate contrast Photonic crystals of woodpile type. We interpret the observations by theoretical and numerical studies.Castellano: Los cristales fotónicos son considerados como materiales prometedores para el control y manipulación del flujo de luz. En este trabajo primero se muestran las evidencias del filtrado espacial de los rayos de luz mediante cristales fotónicos tridimensionales ultra-bajos hechos con vidrio fundido de sílica. Secuencialmente, hemos observado experimentalmente una buena colimaciñon del láser mediante cristales fotónicos de tipo pila. Se interpretan las observaciones tanto con estudios teóricos como estudios numéricos.Català: Els cristalls fotònics són considerats com a materials prometedors per controlar i manipular el fluxe de llum. En aquest treball donem primer les evidències experimentals del filtrat espacial dels rajos de llum mitjançant uns cristalls fotònics tridimensionals de contrast ultra-baix fets en vidre de sílica. Seqüencialment, hem observat experimentalment una bona col·limació del feix del làser per cristalls fotònics de contrast moderat del tipus pila. Interpretem les observacions tant amb estudis teòrics com numèrics