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Experimental study of a phase-sensitive heterodyne detector

Sheng Feng, Heng Fan, and Dechao He

Doc ID: 240919 Received 28 May 2015; Accepted 01 Sep 2015; Posted 01 Sep 2015  View: PDF

Abstract: Although the quantum behaviors of optical detectors has been considered to be fully understood, a fundamental dilemma inevitably arises regarding a phase-sensitive heterodyne detector: On one hand, the detector should suffer 3 dB noise penalty caused by imageband vacuum, on the other hand, it, as a phase-sensitive device, should be noise free at the quantum level. We report on an experiment on the quantum noise performance of a phase-sensitive heterodyne detector. The results show that the quantum noise of the imageband vacuum is absent in the observation. The underlying mechanism behind the observation should be closely related to the origin of the quantum noise in optical detection.

A general relation for optical group delay

Hugo Hoekstra

Doc ID: 243861 Received 29 Jun 2015; Accepted 01 Sep 2015; Posted 01 Sep 2015  View: PDF

Abstract: A quite generally applicable theory is presented for group delay in non-absorbing photonic structures, for which the structural boundaries consist of longitudinally invariant waveguides. It is shown that the sum of the group delays of the various outgoing modes weighted by their transmittances is in general approximately equal to the ratio of time-averaged optical energy and time-averaged input power. It is further demonstrated that exact equality is obtained by taking into account interference effects of modes that have spatial overlap at the structural boundary. A detailed theory is presented, discussed and elucidated via a simple example.

A method of implementing graded index media by symmetry-reduced helical photonic structures

ibrahim halil giden, Hamza Kurt, and behrooz rezaei

Doc ID: 242411 Received 05 Jun 2015; Accepted 31 Aug 2015; Posted 01 Sep 2015  View: PDF

Abstract: We propose a new approach for the realization of graded index (GRIN) medium using symmetry reduced unit element in photonic crystals. Index gradient on the order of Δn=0.16 is achieved without modifying the filling fraction or cell size dimensions. Various beam manipulation techniques can be implemented with such a GRIN medium. We demonstrate that designed GRIN structure may effectively focus incident beam over wide bandwidth. The arrangement of the PC elements within unit-cells exhibits structural order which is helical along the transverse to propagation direction. The designed GRIN PC structurally resembles molecular orientation of cholesteric liquid crystals.

Multiphoton-process-induced coherence effects in a dissipative quantum system

Pradipta Panchadhyayee, Indranil Bayal, Bibhas Dutta, and Prasanta Mahapatra

Doc ID: 242229 Received 02 Jun 2015; Accepted 30 Aug 2015; Posted 01 Sep 2015  View: PDF

Abstract: We have theoretically investigated a number of multiphoton coherence effects in the presence of incoherent pumping in a dissipative quantum system comprised of Er-doped ZBLAN fiber material. For the purpose, we consider a generic four-level ionic model under the semi-classical density matrix formalism whose specialty lies in achieving inversionless gain without any restrictions being imposed on the decay rates of the driven transitions. Many of the coherence effects like absorption cancellation, inversionless gain at the line center, side bands of an absorptive line shape accompanied by dispersive switching are explained using the same model under different parametric conditions. Further, it is shown that modulation in the coherence effects can effectively be controlled by the two- and three- photon excitation mechanisms with special attention to the case of incoherent pumping under stimulated Raman process. The condition of population inversion is found for both coherent as well as incoherent control of stimulated Raman resonance. In addition to Raman gain, gain without inversion in any standard state basis is found to be achieved in our present model.

Simultaneous control of the wavelength and duration of Raman-shifting solitons using topographic photonic crystal fibers

Flavie Braud, Abdelkrim Bendahmane, Arnaud Mussot, and Alexandre Kudlinski

Doc ID: 246572 Received 22 Jul 2015; Accepted 26 Aug 2015; Posted 28 Aug 2015  View: PDF

Abstract: We report an original way to control simultaneously the wavelength and duration of ultrashort solitons by using topographic optical fibers. The design of these longitudinally modulated optical fibers is achieved by using an accurate and simple approach based on analytical and semi-analytical tools, avoiding the use of time-consuming numerical simulations. Starting from realistic initial conditions, we show that the central wavelength of the soliton at the fiber output can be adjusted over more than 200 nm with a duration ranging from 80 fs to 280 fs, respectively. Experimental demonstrations, performed in five different fibers, are in excellent agreement with theoretical predictions, thus validating our approach. This new family of tunable fiber sources can be of great interest for nonlinear microscopy applications.

Transition from saturable to reverse saturable absorption in multi-walled carbon nanotubes doped sol-gel hybrid glasses

Raphi Dror, Mariana Pokrass, ZeeV Burshtein, and Raz Gvishi

Doc ID: 241210 Received 26 May 2015; Accepted 26 Aug 2015; Posted 03 Sep 2015  View: PDF

Abstract: Transition dynamics from optical saturable absorption (SA) to reverse saturable absorption (RSA) in multi-walled carbon nanotubes (MWCNT)-doped fast sol-gel hybrid organic/inorganic glasses was studied by optical transmission of 532-nm laser pulses by exposure to 6-ns long, temporally isolated single pulses of energies between 10-³ and 2×10-² J/cm², and to 1.5-ns long, 11 kHz repetitive pulses, with energies between 2×10-² and 1 J/cm². In the latter mode, RSA gradually develops at a rate that increases with the pulse energy. The SA/RSA transition effects were modeled by a five-level energy scheme. The SA results were analyzed by the slow saturable absorber theory, yielding a ground-state absorption cross-section σgs=1.5×10-¹⁴ cm², for a 2×10¹⁵ cm-³ density of states. The first excited-state absorption cross-section was σes1=9.3×10-¹⁶ cm² for a much higher, 2.3×10¹⁶ cm-³, density of states. The RSA temporal evolution was analyzed by a numerical simulation of the five-level energy scheme, yielding light-intensity dependent parameters: ground-state densities decreasing from 9×10²² cm-³ to 2×10²¹ cm-³; ground-state absorption cross-sections increasing from 2×10-²² cm² to 9×10-²¹ cm²; and excited-state absorption cross-sections increasing from 7.8×10-²² cm² to 3.3×10-²⁰ cm². The occurrence of such huge state densities is consistent with observation by others on the formation of ionized carbon-black particles as plasma states under illumination.

Efficiency limitation for realizing an atom-molecule adiabatic transfer based on a chainwise system

Jingjing Zhai, Lu Zhang, Jing Qian, Weiping Zhang, and Keye Zhang

Doc ID: 243873 Received 01 Jul 2015; Accepted 24 Aug 2015; Posted 01 Sep 2015  View: PDF

Abstract: In a recent work we have developed a robust chainwise atom-molecule adiabatic passage to produce ultracold ground-state molecules via photo-associating free atoms [J. Qian et.al. Phys. Rev. A 81 013632 (2010)]. We find with the help of intermediate auxiliary levels the pump laser intensity in atomic photo-association process can be greatly reduced. In the present, we extend to a more generalized (2n+1)-level system and investigate its efficiency limitation. We show as the increase of intermediate levels the atom-molecule adiabatic passage may break, leading to poor transfer efficiency. We present various optimization approaches for the parameters of middle lasers, involving the order number, relative strength ratio and absolute strength, however, find it is impossible to overcome the transfer efficiency limit given by a three-level Λ system. We also illustrate the importance for experimentalists to select appropriate number of intermediate levels here, for maintaining a highly efficient transfer with less demanding experimental conditions.

Direct production of three color polarization entanglement for continuous variable

zhihui yan and Xiaojun Jia

Doc ID: 241470 Received 21 May 2015; Accepted 24 Aug 2015; Posted 26 Aug 2015  View: PDF

Abstract: The direct generation of discrete variable (DV) three-photon polarization entanglement has been demonstrated [Hamel et al. Nature Photonics 8,801 (2014)], recently. Here, we propose a direct production scheme for continuous variable (CV) three-color polarization entangled states of optical fields. By coupling three strong coherent optical beams and three weak sub-modes of quadrature entangled state, which is generated by a cascaded non-degenerate optical parametric oscillator (NOPO) system, on three polarized beam splitters (PBSs) respectively, and the CV three-color polarization entangled state of optical fields are produced deterministically. The polarization entanglement is verified by inseparability criterion and positive partial transposition (PPT) criterion respectively, and the optimal reachable experimental parameters are obtained through the numerical analysis to provide the direct experimental reference. The CV three color spatially separated polarization entanglement of light can be potentially applied in quantum memory based on the direct interaction of spin of atoms and polarization of light, and long distance local oscillation free quantum communication.

Metasurfaces with Broadband Light Management Ability: A Filter Circuit Theory Based Design

Jierong Cheng and Hossein Mosallaei

Doc ID: 245732 Received 13 Jul 2015; Accepted 22 Aug 2015; Posted 24 Aug 2015  View: PDF

Abstract: We propose broadband metasurfaces with negligible frequency dispersions functioning at mid-infrared and visible spectra using plasmonic and only-dielectric concepts, respectively. The constituting layered elements, with each layer being a capacitive or inductive structure, behave like low-pass circuit filters with maximally flat group delays. The plasmonic layered elements are limited to work around 50 THz due to the appearance of plasmonic resonance feature at higher frequencies. Instead, the only-dielectric concept can be designed up to visible range with negligible material dispersion. Design procedures and working principles are fully detailed. Two types of metasurfaces patterned by plasmonic and only-dielectric elements are carefully designed and numerically simulated around 50 THz and 600 THz, respectively. The structures exhibit wideband characteristics with transmission efficiency above 80%. Chromatic aberration is successfully avoided. Wideband beam scanning performance is observed due to the deep subwavelength thickness and ultra-small element size.

Circular polarization dependent mode hybridization and slow light in vertically coupled planar chiral and achiral plasmonic nanostructures

Minghui Lu, Kun Jiang, Cheng He, Xiaoping Liu, Bo Cui, and Yanfeng Chen

Doc ID: 241029 Received 14 May 2015; Accepted 17 Aug 2015; Posted 19 Aug 2015  View: PDF

Abstract: We numerically studied a square array of plasmonic nanostructures with the unit cell composed of a z-shaped chiral structure and an achiral strip pair. Circular polarization dependent mode hybridization between the z-shaped structure’s radiant mode and the strip pair’s subradiant mode is observed: the resonance amplitudes of two hybrid modes are different for left-handed and right-handed circularly polarized waves, and electromagnetically-induced-transparency-like transparency window is obvious for only one circularly polarized wave. Consequently, slow light with small group velocity is only evident for the corresponding polarization state.

Analysis of a photonic crystal band-edge resonator embedded in a negative electric permittivity medium

Haroldo Hattori

Doc ID: 245900 Received 14 Jul 2015; Accepted 17 Aug 2015; Posted 19 Aug 2015  View: PDF

Abstract: In recent years, artificial structures with negative electric permittivity and/or magnetic permeability, the so-called metamaterials, have been developed. Although many metamaterials are based upon metallic structures, photonic crystals can also exhibit properties such as negative refraction and negative electric permittivity. In this article, the performance of a photonic crystal band-edge resonator embedded in a medium (another photonic crystal structure operating in a conduction band ) with effective negative electric permittivity is studied– an evanescent wave is generated in the negative permittivity medium whose properties are very dependent on the characteristics of the negative electric permittivity medium.

Purcell Enhancement and Focusing Effects in Plasmonic Nanoantenna Arrays

Martin Cryan, Jamie Stokes, Andrei Sarua, Jonathan Pugh, Neciah Dorh, Jack Munns, Philip Bassindale, Nathan Ahmad, and Andrew Orr-Ewing

Doc ID: 238129 Received 15 Apr 2015; Accepted 16 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: This paper presents measured fluorescence results for PMMA-dye coated 5 x 5 gold plasmonic nanoantenna arrays. The paper uses numerical electromagnetic modelling to show how array size and element spacing can be used to control emitted beamshape and compares this with experimental data. The Friis formula from RF antenna theory is used to calculate the intensity enhancement produced by the array. A figure-of-merit is then developed which accounts for the very small mode volume from which the array emission is occurring.

Model for incoupling of etalons into signal strengths extracted from spectral line shape fitting and methodology for predicting the optimum scanning range – Demonstration of Doppler broadened NICE-OHMS down to 9 × 10-14 cm-1

Ove Axner, Isak Silander, and Thomas Hausmaninger

Doc ID: 242076 Received 29 May 2015; Accepted 13 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: Expressions for the in-coupling of white noise and etalons into fitted signal strengths are derived. These show that the amount of noise picked-up is affected by the scanning range. A methodology for finding the optimum scanning range from a single set of measurement has been developed. This was used to estimate the optimum conditions of a noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) setup. The methodology was validated by measurements. This resulted in a spectral noise equivalent absorption per unit length (NEAL) of 2.6 × 10−13 cm-1 Hz-1/2 and a minimum Allan deviation of 9 × 10−14 cm-1 at 30 s, which are the so far lowest reported for Doppler broadened NICE-OHMS.

Experimental realization of positively-momentum-correlated photon pairs from a long periodically poled lithium tantalate crystal

Ping Xu, Marlin Zhong, Shining Zhu, and Liang Lu

Doc ID: 244115 Received 01 Jul 2015; Accepted 12 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We experimentally realized the two-photon entangled state with correlated-momentum and anti-correlated position, namely the counter-Einstein-Podolsky-Rosen (CEPR) state from spontaneous parametric downconversion process in a long periodically poled lithium tantalate (PPLT) crystal with a tightly focused pump beam. The CEPR state is identified by measuring the momentum and position correlations at the Fourier plane and imaging plane of the PPLT crystal end face, respectively, showing a variance product (Δx+)²(Δp_)² = 0:14 ± 0.02h²which fulfils the entanglement criterion. The engineering of such entangled state will bring interests to not only fundamental quantum physics but the applied quantum technologies such as quantum imaging etc

Observation of elliptical rings in Type-I spontaneous parametric down-conversion

Hannah Guilbert, Daniel Gauthier, and Yu-Po Wong

Doc ID: 238083 Received 21 Apr 2015; Accepted 11 Aug 2015; Posted 17 Aug 2015  View: PDF

Abstract: We investigate the transverse spatial profile of down-converted light produced by noncollinear, degenerate, Type-I spontaneous parametric down-conversion in two types of nonlinear crystals. We find that the pattern produced by one crystal, beta barium borate (BBO), produces a circular down-conversion pattern while the other crystal, bismuth triborate (BiBO) produces an elliptical pattern. We show this difference is due to the angle-independent refractive index experienced by the daughter photons in BBO, while they experience an angle-dependent refractive index in BiBO. We image the transverse spatial profile of the generated light to determine the eccentricity produced by each crystal and develop a model to explain our observation. Among other things, this model predicts that there is a wavelength for which the eccentricity from BiBO is nearly zero. Finally, we discuss how the elliptical ring pattern produced in BiBO potentially affects polarization entanglement for experimental setups that collect biphotons around the entire down-conversion ring. We show that the quality of polarization entanglement as measured by the overlap integral of the spectrum of the two rings, can remain high ($>99.4\%$) around the entire ring at the expense of decreased biphoton rate.

Nonlinear Duffing Oscillator Model for Third Harmonic Generation

Michael Scalora, Maria Antonietta Vincenti, Domenico de Ceglia, Crina Cojocaru, Marco Grande, and Joseph Haus

Doc ID: 242664 Received 09 Jun 2015; Accepted 07 Aug 2015; Posted 21 Aug 2015  View: PDF

Abstract: We employ a classical, nonlinear Lorentz-Duffing oscillator model to predict third harmonic conversion efficiencies in the ultrafast regime, from a variety of metal nanostructures, including smooth, isolated metal layers, a metal-dielectric photonic band gap structure, and a metal grating. As expected, the plasmonic grating yields the largest narrow-band conversion efficiencies. However, interference phenomena at play within the multilayer stack yield comparable, broad-band conversion. The method includes both linear and nonlinear material dispersions that in turn sensitively depend on linear oscillator parameters. Concurrently, and unlike other techniques, the integration scheme is numerically stable. By design, one thus avoids the introduction of explicit, third-order nonlinear coefficients and also takes into account linear and nonlinear material dispersions simultaneously, elements that are often necessary to fully understand many of the subtleties of the interaction of light with matter.

Optical Characterization of Epsilon-Near-Zero, Epsilon-Near-Pole and Hyperbolic Response in Nanowire Metamaterials

Zubin Jacob, Ryan Starko-Bowes, Jon Atkinson, Ward Newman, Huan Hu, Efthymios Kallos, George Palikaras, Robert Fedosejevs, and Sandipan Pramanik

Doc ID: 228922 Received 04 Dec 2014; Accepted 30 Jul 2015; Posted 17 Aug 2015  View: PDF

Abstract: We report on the optical and physical characterization of metallic nanowire (NW) metamaterials fabricated by electrodeposition of ≈ 30 nm diameter gold nanowires in nano-porous anodic aluminum oxide. We observe a uniaxial anisotropic dielectric response for the NW metamaterials that displays both epsilon-near-zero (ENZ) and epsilon-near-pole (ENP) resonances. We show that a fundamental difference in the behavior of NW-metamaterials from metal-dielectric multilayer (ML) metamaterials is the differing directions of the epsilon-near-zero (ENZ) and epsilon-near-pole (ENP) dielectric responses relative to the optical axis of the effective dielectric tensor. In contrast to multilayer metamaterials, nanowire metamaterials exhibit an omnidirectional ENP and an angularly dependent ENZ. Also in contrast to ML metamaterials, the NW metamaterials exhibit ENP and ENZ resonances that are highly absorptive and can be effectively excited from free space. Our fabrication allows a large tunability of the epsilon-near-zero resonance in the visible and near IR spectrum from 583 nm to 805 nm as the gold nanorod fill fraction changes from 26% to 10.5%. We support our fabrication process flow at each step with rigorous physical and optical characterization. Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) analyses are used to ascertain the quality of electrochemically deposited Au nanowires prior to and after annealing. Our experimental results are in agreement with simulations of the periodic plasmonic crystal and also analytical calculations in the effective medium metamaterial limit. We also experimentally characterize the role of spatial dispersion at the ENZ resonance and show that the effect does not occur for the ENP resonance. The application of these materials to the fields of biosensing, quantum optics and thermal devices shows considerable promise.

Manipulation of Light Propagation in Photonic Crystal

Zhiyuan Yang, Amitabh Joshi, Rena Kasumova, and Yuri Rostovtsev

Doc ID: 237240 Received 07 Apr 2015; Accepted 20 Jul 2015; Posted 21 Aug 2015  View: PDF

Abstract: The propagation of probe electromagnetic waves has been investigated in a heterostructure formed by layers having linear and nonlinear optical properties. The appearance of a forbidden band gap for the probe electromagnetic field induced by another control electromagnetic field has been shown that leads to the trapping of the probe pulse inside the structure. Switching off the control field leads to resuming the propagation of the probe pulse. Implimentation of nonlinear layer has been suggested.

Two-mode squeezed states as Schr\"odinger-cat-like states

Florian Fröwis, Enky Oudot, Pavel Sekatski, Nicolas Gisin, and Nicolas Sangouard

Doc ID: 235724 Received 05 Mar 2015; Accepted 17 Jul 2015; Posted 27 Aug 2015  View: PDF

Abstract: In recent years, there has been an increased interest in the generation of superpositions of coherent states with opposite phases, the so-called photonic Schr\"odinger-cat states. These experiments are very challenging and so far, cats involving only small photon numbers have been implemented. Here, we propose to consider two-mode squeezed states as examples of Schr\"odinger-cat-like states. For that, we apply criteria that aim to identify macroscopic superpositions in a more general sense. We extend some of these criteria to the two-mode, continuous variable regime. Furthermore, we compare the size of states obtained in several experiments and discuss experimental challenges for further improvements. Our results do not only promote two-mode squeezed states for exploring quantum effects at the macroscopic level but also provide direct measures to evaluate their usefulness for quantum metrology.

Nonlinear energy transfer in quantum dot and metallic nanorod nanocomposites

Mahi Singh and Chris Racknor

Doc ID: 236213 Received 16 Mar 2015; Accepted 08 Jun 2015; Posted 17 Aug 2015  View: PDF

Abstract: We have investigated the nonlinear energy transfer in a quantum dot (QD) and metallic nanorod (MNR) nanocomposite. A intense probe laser field is applied to monitor two-photon energy transfer from QD to MNR and a control laser field is applied to control the energy transfer rate. Induced dipoles are created in the QD and MNR and these dipoles are interacting with each other. Surface plasmon-polaritons are also created in the MNR due to a coupling of charge fluctuations and external laser fields. Therefore, there is an interaction between excitons in QD and surface plasmon-polaritons in MNR. This interaction is called the dipole-dipole interaction. Due to this interaction the two-photon energy is transferred from the QD to MNR. Using the density matrix method the energy transfer rate between the components of the system is evaluated. It is found that the energy transfer rate has one peak due to the transfer of the two-photon energy from the QD to MNR when the control field is absent. When the control field is applied this peak disappears. This means no energy transfer between two nanosystems. However two new peaks appear in the energy transfer rate at two different energies. It is also found that by varying he intensity of the probe field one can also control the energy transfer from the QD to the MNR. These are interesting findings of the paper and they can be used to fabricate nanosensors, nano-switches and energy transfer devices.

Comment on "Temporal cavity soliton formation in an anomalous dispersion cavity fiber laser"

Stefan Wabnitz

Doc ID: 230727 Received 11 May 2015; Accepted 26 May 2015; Posted 19 Aug 2015  View: PDF

Abstract: A recent paper [Tang et al., J. Opt. Soc. Am. B, Vol. 31, No. 12, 3050-3056 (2014)] reports the experimental observation of the generation of stable pulse trains in a ring fiber laser. Contrary to what is stated, the theory published in that paper does not support the claim that the generation mechanism of the pulse train is the cavity-induced modulation instability effect.

Saturable and inverse saturable absorption in multi-walled-carbon-nano-tubes-doped fast Sol-gel hybrid glasses

Raphi Dror, ZeeV Burshtein, Raz Gvishi, and Mariana Pokrass

Doc ID: 232480 Received 14 Jan 2015; Accepted 10 Apr 2015; Posted 10 Apr 2015  View: PDF

Abstract: Dynamics of saturable absorption and inverse saturable absorption of Multi walled carbon nano tubes (MWCNT)-doped fast Sol-gel hybrid glasses was studied by optical transmission of 532-nm laser beam pulses at two extreme conditions: 6-ns long temporally isolated single pulses up to 0.02 J/cm2, and a pulse train at different intensities in the range 0.72-10.7 kW/cm2 (quasi-CW illumination). The temporally isolated single pulses were analysed by the slow saturable absorber limit; The quasi-CW illumination at steady state was analysed by the fast inverse saturable absorber limit. A fresh, corrected solution to the rate equation was developed for the latter. The time dependence of reaching steady state absorption in the quasi-CW case was analysed by a numerical simulation of a state model. The single-pulse case analysis yields a ground-state density N=5.1×1015cm-3, a ground-state absorption cross-section σgs=5.5×10-15cm2 , and a first excited-state absorption cross-section σes1=3.6×10-15cm2. The quasi-CW case analysis is consistent with the occurrence of the MWCNT transition upon illumination into a highly absorbing/scattering state ("plasma" state). The analysis yields a ground-state concentration estimation N=3.2×1015cm-3, and a ground-state absorption cross-section σgs=6.3×10-15cm2. The "plasma" lower-state absorption/ scattering cross-section is σes2=2.3×10-14cm2. The light-intensity dependent transition rate between the first MWCNT excited-state and its "plasma" lower state followed the relation τ-1inc[s-1]=12.25exp(4×10-7I[W/cm2]); the transition rate between the lowest "plasma" state and the MWCNT ground-state, was also light-intensity dependent, following the relation τ-1[s-1]=3.5exp(2.54×10-7I[W/cm2]).

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