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Accepted papers to appear in an upcoming issue

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Nonlinear optical memory: Theory and Experiment

Gabriel Borba, Jose Tabosa, and Daniel Barbosa

Doc ID: 305037 Received 17 Aug 2017; Accepted 19 Oct 2017; Posted 20 Oct 2017  View: PDF

Abstract: The present work explores new possibilities for the selective storage of optical information through higher-order nonlinearities in a sample of cold cesium atoms obtained from a magneto-optical trap. Particularly, we demonstrate the storage of a third, fifth, and seventh order nonlinear atom-light interaction into the coherences and populations of the Zeeman structure of the hyperfine cesium $6S_{1/2}$, $F=3$ ground state. Two writing beams create coherence and population gratings associated with high-order nonlinear processes, which can be selectively retrieved by a reading beam after a controllable storage time. Each kind of grating can store only specific orders of the nonlinear interaction, leading to special features in each signal. Applications of this nonlinear memory to herald multiphotons are discussed.

Rotational synchronization of two non-contact nanoparticles

Vahid Ameri and M Eghbali-Arani

Doc ID: 305038 Received 17 Aug 2017; Accepted 18 Oct 2017; Posted 18 Oct 2017  View: PDF

Abstract: Proposing a system of two rotatable nanoparticles (NPs) in the presence of electromagnetic vacuum fluctuations, using the framework of canonical quantization, the electromagnetic and matter fields have been quantized. The non-contact frictional torque, affecting the rotation of NPs due to the presence of electromagnetic vacuum fluctuations and also by the matter field fluctuations have been derived. Considering the distance between NPs less than 100 nm in the near-field, we observe the rotations are phase locked. It has been shown that the electromagnetic vacuum fluctuations play the role of noises to break down the synchronization. Also surprisingly, we find the frictional torque between NPs in the near-field is much bigger than the popular contact friction between them where it causes a robust synchronization in the near-field.

Analog curved spacetimes in the reversed dissipation regime of cavity optomechanics

Foroud Bemani, Rasoul Roknizadeh, and M. H. Naderi

Doc ID: 301648 Received 06 Jul 2017; Accepted 16 Oct 2017; Posted 17 Oct 2017  View: PDF

Abstract: In this paper, we theoretically propose an optomechanical scheme to explore the possibility of simulating the propagation of the collective excitations of the photon fluid in a curved spacetime. For this purpose, we introduce two theoretical models for two-dimensional photon gas in a planar optomechanical microcavity and a two-dimensional array of coupled optomechanical systems. In the reversed dissipation regime (RDR) of cavity optomechanics where the mechanical oscillator reaches equilibrium with its thermal reservoir much faster than the cavity modes, the mechanical degrees of freedom can adiabatically be eliminated. The adiabatic elimination of the mechanical mode provides an effective nonlinear Kerr-type photon-photon interaction. Using the nonlinear Schr\"{o}dinger equation (NLSE), we show that the phase fluctuations in the two-dimensional photon fluid obey the Klein-Gordon equation for a massless scalar field propagating in a curved spacetime. The results reveal that the photon fluid as well as the corresponding metric can be controlled by manipulating the system parameters.

Amplified spontaneous emission at 5. μm in two-photon excited Rb vapour

Alexander Akulshin, Nafia Rahaman, Sergey Suslov, and Russell McLean

Doc ID: 304189 Received 08 Aug 2017; Accepted 16 Oct 2017; Posted 17 Oct 2017  View: PDF

Abstract: Population inversion on the 5D5/2-6P3/2 transition in Rb atoms produced by cw laser excitation at different wavelengths has been analyzed by comparing the generated mid-IR radiation at 5. μm originating from amplified spontaneous emission (ASE) and isotropic blue fluorescence at 420 nm. Using a novel method for detection of two photon excitation via ASE, we have observed directional co- and counter-propagating emission at 5. μm. Evidence of a threshold-like characteristic is found in the ASE dependences on laser detuning and Rb number density. The power dependences of the backward- and forward-directed emission can be very similar, however their spectral dependences are not identical. A new type of temporally and spatially coherent radiation is suggested.

The Transition Dynamics of Bright Soliton in a Binary Bose-Einstein Condensate

Li-Chen Zhao, Guo-Guo Xin, and Zhan-Ying Yang

Doc ID: 303626 Received 28 Jul 2017; Accepted 16 Oct 2017; Posted 16 Oct 2017  View: PDF

Abstract: Transition or tunneling dynamics have been studied widely in two-mode Bose-Einstein condensate systems with linear coupling effects. Nonlinear interaction between atoms would induce nonlinear Josephson oscillation which admits the oscillation form different from the classical Josephson oscillation. Similar extensions for Rosen-Zener tunneling and Landau-Zener tunneling also suggest that strong nonlinear strength would induce nonlinear type transition dynamics, in sharp contrast to the linear process. Interestingly, here we show a standard Josephson oscillation with constant linear coupling strength, no matter how strong the nonlinear interaction strength is. This character is in sharp contrast to the nonlinear Josephson oscillation reported before in nonlinear coupled systems. Through manipulating the linear coupling strength by RF field, we demonstrate that the Rosen-Zener transition particles, with an invariant distribution profile, can be managed well under exponential and periodic forms. Nonlinear interaction strength with the equal values are found to have no effects on the transition rate between atoms in the two components. The results are helpful for controllable population transfer between quantum states.

Design of high-forward-transmission all-optical diode based on cascaded side-coupled photonic crystal cavities

Takanori Sato, Takeshi Fujisawa, and Kunimasa Saitoh

Doc ID: 304945 Received 28 Aug 2017; Accepted 13 Oct 2017; Posted 16 Oct 2017  View: PDF

Abstract: A high-forward-transmission all-optical diode based on the cascaded photonic crystal cavities is proposed. To obtain the high-forward transmission and large nonreciprocity, we generate the box-like spectrum by cascading two side-coupled photonic crystal cavities. We find that, by appropriately adjusting the distance between two cavities, the high contrast of the transmission and the flat spectral lineshape with almost 100% transmission can be obtained. These characteristics are preferable for achieving the high-forward transmission and large nonreciprocity. Numerical results show that the designed all-optical diode performs the perfect transmission with the large nonreciprocal transmission ratio (NTR) of > 50dB.

Phase-controlled electromagnetically induced focusing in a closed-loop atomic system

Zahra Amini sabegh, Mohammad Ali Maleki, and Mohammad Mahmoudi

Doc ID: 302134 Received 10 Jul 2017; Accepted 11 Oct 2017; Posted 13 Oct 2017  View: PDF

Abstract: We study the electromagnetically induced focusing in a four-level closed-loop atomic system. It is shown that the full width at half maximum (FWHM) of the focused output probe intensity profile in the focal plane can be controlled by intensity profile and relative phase of applied fields. It is demonstrated that the FWHM of the focused output probe intensity profile in the focal plane is much smaller than that of the input probe intensity and the minimum value of FWHM is obtained for special set of parameters. Moreover, the FWHM decreases by increasing the Rabi frequency of the Gaussian signal field. For the selected parameters the Gaussian probe intensity profile switches to a doughnut-like intensity profile, just by changing the relative phase of applied fields. Finally, we apply a Laguerre-Gaussian signal field and find out that the characteristics of output probe field depend on the intensity profile of the signal field. Our results can be used to design a lens-like device with controllable focal length and focusing strength which is useful in all-optical switching.

Voltage-driven MOKE in glass/Au/NiFe/oxide/WS2 magneto-plasmonic FET

Ehsan Faridi and Seyed Majid Mohseni

Doc ID: 303388 Received 08 Aug 2017; Accepted 08 Oct 2017; Posted 09 Oct 2017  View: PDF

Abstract: The current study was undertaken to design a novel state of the art of optoelectronic device for the voltage-driven transverse magneto-optical Kerr effect (TMOKE). The suggested structure is a glass/Au/NiFe/oxide/WS₂ field-effect transistor magneto-plasmonic multilayer with an Au plasmonic and gate layer, a NiFe ferromagnetic layer, an oxide voltage-driven layer and WS2 refractive index and an absorption/reflection controlled layer. Transfer matrix calculations indicate that a large increase in TMOKE can be predicted as the result of large changes in the refractive index of the WS₂ monolayer as recently reported [1] . Oxide layers having different thicknesses were examined to increase the TMOKE response and deepen reflectance. The results offer design options for novel multifunctional optoelectronic devices.

Deep Laser Cooling of Rare-Earth Doped Nanocrystals in Radio Frequency Trap

Seimion Rudiy, Tatiana Vovk, Anton Kovalev, Vadim Polyakov, Andrei Ivanov, Evgeniy Perlin, and Yuri Rozhdestvensky

Doc ID: 306727 Received 13 Sep 2017; Accepted 07 Oct 2017; Posted 09 Oct 2017  View: PDF

Abstract: We study hybrid optical cooling of rare-earth-doped mesoscopic crystals via the anti-Stokes fluorescence and collective photon recoil effect inside them. The proposed cooling scheme, composed of a radio-frequency trap and a three-dimensional optical potential, makes it possible to cool doped nanocrystals down to an external temperature of 10⁻⁸ K. By achieving the mechanical action values of ~10ℏ, we come close to the macroscopic quantum states of a solid matter. Such deep translational cooling of nanocrystals paves the way to fundamental studies on the solid state and to applications in low-temperature chemistry and biophysics.

Bending reorientational solitons with modulated alignment

Filip Sala, Noel Smyth, Ula Laudyn, Miroslaw Karpierz, Antonmaria Minzoni, and Gaetano Assanto

Doc ID: 304855 Received 15 Aug 2017; Accepted 06 Oct 2017; Posted 06 Oct 2017  View: PDF

Abstract: While curved waveguides are fundamental elements in photonics, those induced all-optically in nonlinear uniform dielectrics tend to be straight. In uniaxial soft matter with a reorientational response, such as nematic liquid crystals, light beams in the extraordinary polarization undergo self-focusing via an increase in refractive index and eventually form spatial solitons, i.e., self-induced waveguides. Hereby we investigate the bending of such waveguides by analyzing the trajectory of solitons in nematic liquid crystals--- nematicons--- in the presence of a linearly varying transverse orientation of the optic axis. To this extent we use and compare two approaches: i) a slowly varying (adiabatic) approximation based on momentum conservation of the nematicon in a Hamiltonian sense; ii) the Frank-Oseen elastic theory coupled with a fully vectorial and nonlinear beam propagation method. The models provide comparable results in such a non-homogeneously oriented uniaxial medium and predict bent soliton paths with either monotonic or non-monotonic curvatures, enabling the design of curved channel waveguides induced by light beams.

Modulation instability in collinear three-core optical fibers

Jin Hua Li, Kin Chiang, and Chao Ran Li

Doc ID: 296771 Received 25 May 2017; Accepted 06 Oct 2017; Posted 13 Oct 2017  View: PDF

Abstract: Modulation instability (MI) in a collinear three-core optical fiber (CLTCF), namely an optical fiber that consists of three identical cores aligned symmetrically along a straight line, is analyzed in detail for the symmetric and antisymmetric continuous-wave (CW) states in the normal and anomalous dispersion regimes. The symmetric CW state, where the fields in the two side cores are identical, exists only with certain combinations of powers in the side cores and the center core within a limited range of total power and these characteristics are governed by the linear coupling and the nonlinear coefficient of the fiber. The symmetric CW state generates MI characteristics not observed previously. In the anomalous dispersion regime, as the total power increases from a threshold value, three MI bands are generated and then merge rapidly into a single band and the MI gain is insensitive to the linear coupling coefficient and the coupling-coefficient dispersion (CCD) of the fiber. In the normal dispersion regime, the generation of MI depends critically on the CCD. Two MI bands are generated from the CCD at a total power smaller than a critical value that depends on the linear coupling, the dispersion, and the nonlinear coefficient of the fiber. No MI can be generated without CCD. The antisymmetric CW state, where the fields in the two side cores have equal amplitudes of opposite signs and the field in the center core is zero, exists at any power. For this state, the MI characteristics are qualitatively similar to those of an equilateral three-core fiber. The study also includes direct numerical verification of the MI analysis with wave propagation simulation.

Tunable Fano-like resonance analysis based on the system consisting of two silica microdisks-coupled Mach-Zehnder interferometer and graphene

Huibo Fan, Li Fan, Changquan Xia, Lichun Wang, and Mingya Shen

Doc ID: 303200 Received 26 Jul 2017; Accepted 05 Oct 2017; Posted 06 Oct 2017  View: PDF

Abstract: We theoretically demonstrate a significant system to realize asymmetric Fano-like resonance by coupling two silica microdisks with a fiber Mach-Zehnder interferometer (MZI), which could also be modulated by the graphene with electro-optic effect. Microdisks are respectively and evanescently coupled with the two arms of MZI. Depending on the coupling strength between microdisks and the fiber tapers, the diameters of microdisks, and the intrinsic quality factors of microdisks, transmission spectra of MZI exhibit the resonance peak, the resonance dip, and the Fano-like resonance. In addition, by introducing the graphene with electro-optic effect, quality factor and resonant wavelength of one microcavity are modulated, consequently also varying the Fano-like lineshapes. This asymmetric Fano-like resonance with the advantages of fiber or waveguide integration, ease of operation, and convenient controllability of lineshape could have great potential in high-performance sensing, optical switching, and optical signal processing.

Analysis of narrow linewidth fiber laser using double subring resonators

nastaran pourshab, Asghar Gholami, Mohammad Javad hekmat, and narges shahriyari

Doc ID: 292484 Received 10 Apr 2017; Accepted 03 Oct 2017; Posted 04 Oct 2017  View: PDF

Abstract: In this paper, a narrow linewidth fiber laser based on subring resonators is proposed using two different lengths of coupled subring resonators and a fiber Bragg grating. The laser physical operation is modeled using rate equations, considering the optical signal spectrum and subring resonators effects on the laser output linewidth. To verify the model, the proposed fiber laser is implemented, and its measured results are compared with the model results. For the implemented single mode laser, the laser linewidth less than 10 KHz with a 60dB of signal-to-noise ratio was achieved. Moreover the output powers up to 25mW at 1550nm were obtained for 300mW pumped power at 980nm.

Nonlocal effect on the transmission of transverse electric electromagnetic wave through periodic dielectric-metal multilayers

Denis Iakushev and Servando Lopez-Aguayo

Doc ID: 304741 Received 15 Aug 2017; Accepted 03 Oct 2017; Posted 04 Oct 2017  View: PDF

Abstract: The problem of electromagnetic response of periodic dielectric-metal structure to transverse electric electromagnetic excitation is solved analytically on the basis of the Boltzmann kinetic equation formalism. We analyse both dispersion relation and transmission coefficient for different angles of incidence. We show that due to nonlocal dependence of the electron current density on electric field in metal layers, the THz and near-infrared photonic properties of dielectric-metal structures are strikingly different from those obtained with the use of the simplified description based on the Drude-Lorentz model. In the limit of weak spatial nonlocality, the developed theory reproduces the known results for transverse electric electromagnetic waves incident on bi-layer photonic crystal consisting on spatially local media.

Tunable dual-channel filter based on add-drop resonator Sagnac interferometer

Kai Ma, Yundong Zhang, Yongfeng Wu, Huaiyin Su, Xuenan Zhang, and Ping Yuan

Doc ID: 303179 Received 25 Jul 2017; Accepted 01 Oct 2017; Posted 02 Oct 2017  View: PDF

Abstract: In this paper, we propose an add-drop resonator Sagnac interferometer filter to achieve tunable dual-channel function. Not only is just one ring utilized to control two channels, but also the reconfiguration is viable by phase difference control. Three methods are put forward to tune the bandwidth, the extinction ratio, and the reconfiguration of the channels. The reconfiguration of the dual-channel is realized via controlling the phase difference between the two arms of the Sagnac interferometer, avoiding the traditional method of shifting the resonance wavelength. Furthermore, the channels can be extended by adding add-drop interferometers. The flexible and compact filter can provide potential implications in dense wavelength division multiplexing (DWDM) system and optical switches. © 2015 Optical Society of America

Propagation of twin-beam state from the near-field to far-field

Justinas Galinis and Ondrej Haderka

Doc ID: 301180 Received 12 Jul 2017; Accepted 24 Sep 2017; Posted 25 Sep 2017  View: PDF

Abstract: Evolution of twin-beam state propagating in the free space are investigated theoretically using Schmidt decomposition method. Influence of the spatially chirped pump beam on the twin beams is discussed. We use theoretical model to analyze and discuss the experimental results of the twin-beam properties in the transition from the near-field to far-field regime published by Haderka et al [Sci. Rep., 5, 14365 (2015)]. Evolution of both radial and azimuthal cross-correlations from near-field to far-field is investigated discussing influence of the pump spatial spectrum and the phase matching conditions.

Entanglement detection via atomic deflection

Carlos Máximo, Romain Bachelard, Gentil de Moraes Neto, and Miled Moussa

Doc ID: 302916 Received 21 Jul 2017; Accepted 13 Sep 2017; Posted 11 Oct 2017  View: PDF

Abstract: We report on criteria to detect entanglement between the light modes of two crossed optical cavities by analyzing the transverse deflection patterns of an atomic beam. The photon exchange between the modes and the atoms occurs around the overlapping nodes of associated standing waves, which generates the two-dimensional (2D) version of the Optical Stern-Gerlach (OSG) effect. In this optical cross-cavity setup, we show that the discrete signatures of the fields states, left in the momentum distribution of the deflected atoms, may reveal entanglement for a certain class of two-mode states. For a single photon, we present the possibility of quantifying entanglement by the rotation of the momentum distribution. For a larger number of photons, we demonstrate that quantum interference precludes the population of specific momentum states revealing maximum entanglement between the light modes.

Ho3+ doped ZnO nano phosphor for low-threshold sharp red light emission at elevated temperatures

M. S. Ramachandra Rao and Fabitha K

Doc ID: 300997 Received 26 Jun 2017; Accepted 12 Aug 2017; Posted 10 Oct 2017  View: PDF

Abstract: As an approach to design efficient visible luminescent material at nano scale, Ho3+ ion doped single phase ZnO nano phosphor to obtain red emission LED/laser is reported. Ho3+ doped ZnO nanoparticles with various concentrations of Ho3+ have been prepared by simple sol-gel synthesis technique. Under the excitation of 488 nm, the PL emission spectra of the nano phosphor exhibit an intense emission with multiple and well resolved narrow splitting peaked in the range from 640-667 nm, which is identified as the emission from the Ho3+ ion, corresponding to 5F5  5I8 transition with multiple splitting due to ZnO crystal field. The required excitation threshold for these emissions is surprisingly as low as 33.8 kW/cm2 and the narrow line width (FWHM < 2 nm) is found to be persistent even at higher temperatures. Such sharp emission from Ho3+:ZnO nanoparticles could be used for lasing application.

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