1,721,129 research outputs found
Surface guided modes in photonic crystal ridges: the good, the bad, and the ugly
No full textWe discuss the existence and the optical properties of guided modes in photonic crystal ridges, where light confinement relies on a photonic band gap in the direction of the substrate and on total internal reflectance in the other directions. Photonic crystal ridges are known to support guided surface waves, but here we show that at least three different guided modes can be identified, and only one of them seems to possess all the characteristics of a proper guided surface wave. We also discuss the use of effective index approaches to drastically simplify the modeling of such modes. Photonics crystal ridges are already recognized as promising platforms in the field of optical sensing and for the study of the light-matter interaction at the fundamental level, and our results should be of use in exploiting the potential of these structures for the confinement and control of light
Highly efficient second-harmonic generation in doubly-resonant planar microcavities
No full textA theoretical study of second-harmonic generation in planar microcavities with periodic dielectric mirrors is made. Strong enhancement of the nonlinear conversion is predicted when double resonance for the pump and harmonic fields, as well as phase matching, are achieved. For a given structure design, the finite angle of incidence is used as a tuning parameter and the splitting between cavity modes with different polarizations is used to compensate the material dispersion. Examples are given for GaAs cavities with AlGaAs/Alox dielectric mirrors
Long-range Bloch surface waves in photonic crystal ridges
No full textWe theoretically study light propagation in guided Bloch surface waves (BSWs) supported by photonic crystal ridges. We demonstrate that low propagation losses can be achieved just by a proper design of the multilayer to obtain photonic band gaps for both light polarizations. We present a design strategy based on a Fourier analysis that allows one to obtain intrinsic losses as low as 5 dB/km for a structure operating in the visible spectral range. These results clarify the limiting factors to light propagation in guided BSWs and represent a fundamental step towards the development of BSW-based integrated optical platforms
Second-harmonic generation in doubly-resonant microcavities with periodic dielectric mirrors
No full textStrong enhancement of second-harmonic generation (SHG) is expected in one-dimensional microcavities when double resonance for the pump and the harmonic fields, as well as phase matching, are achieved. The realization of a doubly resonant microcavity with dielectric mirrors made of nonbirefringent materials is difficult because of the refractive index dispersion of the constituent media. Here we present a powerful method, based on photonic crystal concepts like gap maps and their generalization to defect modes, for the
design of doubly resonant microcavities with periodic dielectric mirrors. The material dispersion is compensated
by using the angle of incidence as a tuning parameter, thanks to the polarization splitting of cavity modes.
The cavity enhancement of SHG increases exponentially with the number of periods in the dielectric mirrors
and can be much larger than in single-resonant microcavities with comparable -or even larger- quality factors. The roles of phase delay and of thin versus thick configurations in the dielectric mirrors, of the growth orientation, and of the polarization degrees of freedom in achieving double resonance with phase matching are discussed. Significant examples of doubly resonant SHG with high conversion efficiency are given for Al0.25Ga0.75As cavities with Al0.4Ga0.6As/Alox (oxidized AlAs) mirrors
Quasiguided surface plasmon excitations in anisotropic materials
No full textWe present a theoretical study of surface plasmon polaritons in a configuration where a metal layer is bounded by a homogeneous anisotropic dielectric. We consider uniaxial and biaxial dielectrics with the optical axis lying in the plane defined by the metal/dielectric interface. Through a systematic study of the in-plane surface plasmon dispersion relation we confirm the existence of several propagation regimes for different values and signs of the birefringence. We report the discovery of the existence of quasiguided surface plasmon polaritons characterized by non-null radiative components. We identify the conditions for the existence of such modes, and explain their peculiar properties in terms of the hybridization of radiative and guided modes
Narrow-band photon pair generation through cavity-enhanced spontaneous parametric down-conversion
No full textCavity-enhanced spontaneous parametric down-conversion (SPDC) can be used to implement heralded single-photon sources with narrow bandwidth down to tens of megahertz, thus compatible with atom-based quantum memories. In this work, we propose and study the cavities that are either singly resonant at the frequency of only one of the generated photons or doubly resonant at the frequency of one generated photon and for the pump field. We derive analytical expressions for the generation rate and the spectral brightness as a function of the main structure parameters. Our analysis shows that by exploiting counterpropagating SPDC inside a cavity with properly designed distributed Bragg reflectors, pure narrow-band heralded single photons can be generated. In particular, when a pulsed pump illuminates a 1-mm-long singly resonant cavity, the bandwidth of the resonant and the nonresonant photons will be 120 MHz and 5.7 GHz, respectively, with heralded single-photon purity as high as 0.993. Due to its small absorption probability inside the cavity, the heralding efficiency can approach unity if the nonresonant partner is used as a heralded single photon. Finally, we also show that continuous-wave excitation of a 1-cm-long cavity resonant for the pump and copropagating fields can provide photon pairs in a narrow bandwidth of 10 MHz with spectral brightness as high as 2×106 (smWMHz)-1. This source can efficiently couple with quantum memories and can find applications in quantum information processing and communication
Stimulated Emission Tomography
No full textWe identify a relation between the number of photon pairs generated by parametric fluorescence, through either spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing, and the number generated by the corresponding stimulated process, respectively, either difference-frequency generation or stimulated four-wave mixing. On the basis of this very general result, we show that the characterization of SPDC sources of two-photon states in a given system can be performed solely by studying stimulated emission. We call this technique stimulated emission tomography (SET). We show that the number of photons detected in SET can be 9 orders of magnitude larger than the average number of coincidence counts in two-photon quantum state tomography. These results open the way to the study of sources of quantum-correlated photon pairs with unprecedented precision and unparalleled resolution. © 2013 American Physical Society
Enhancement of diffraction for biosensing applications via Bloch surface waves
No full textWe propose a biosensor based on the diffraction of Bloch surface waves (BSWs) in periodic dielectric stacks. Significant enhancement of diffraction efficiency by a biomolecule grating placed on the multilayer is predicted when a BSW is excited through a prism in the Kretschmann configuration. Numerical calculations for BSW in a Si/SiO(2) dielectric stack show an increase of diffraction intensity up to three orders of magnitude with respect to the case of surface plasmon wave enhancement. The mechanism that leads to large field confinement and the absence of absorption losses in the dielectric system make this solution flexible and suitable to different grating periods
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