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Accepted papers to appear in an upcoming issue

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Dual-pump frequency comb generation in normally dispersive optical fibers

Aku Antikainen and Govind Agrawal

Doc ID: 241534 Received 26 May 2015; Accepted 01 Jul 2015; Posted 01 Jul 2015  View: PDF

Abstract: We show that tunable frequency combs can be generated by launching two continuous-wave pumps at slightly different wavelengths into a normally dispersive optical fiber. The dual-pump configuration allows the tuning of comb spacing into the terahertz regime. Different pump powers and frequency separations are explored numerically to determine the effect of the input parameters on frequency comb generation. The relative power of the two pumps is found to be a critical factor through its crucial effect on optical wave breaking. Pump powers and fiber length are shown to have a significant effect on the comb width as well. Unlike in the case of supercontinuum generation, Raman scattering is found to have a negligible or even a slightly detrimental effect. Our findings also help bridge the gap between work done on the propagation of a single pulse and the evolution of dual-pump signals in normally dispersive highly nonlinear fibers.

Tunable optomechanically induced absorption with quantum fields in an optomechanical system

Qin Wu

Doc ID: 240410 Received 11 May 2015; Accepted 01 Jul 2015; Posted 02 Jul 2015  View: PDF

Abstract: We report the optomechanically induced absorption (OMIA) using a narrowband squeezed field in a optomechanical cavity coupled to an external charged nanomechanical resonator through Coulomb interaction. Our OMIA might be applied to detect the Coulomb coupling strength by measuring the distance between two points with absorption minima of the homodyne spectrum which varies near linearly with the Coulomb force. Especially, the model under our consideration can simulate the quantum signal fighting against the environment noise using squeezed field.

Carrier field shock formation of long wavelength femtosecond pulses in single crystal diamond and air

Paris Panagiotopoulos, Jerome Moloney, Patrick Whalen, and Miroslav Kolesik

Doc ID: 240513 Received 15 May 2015; Accepted 30 Jun 2015; Posted 01 Jul 2015  View: PDF

Abstract: We numerically demonstrate the formation of carrier field shocks in single crystal diamond and air for a wide variety of input conditions using two different electric field propagation models. We investigate the impact of numerous physical effects on the carrier wave shock. It is shown that in many cases a field shock is essentially unavoidable and therefore extremely important in the propagation of intense long wavelength pulses in weakly dispersive nonlinear media. We found that single crystal diamond is the ideal nonlinear medium for carrier wave shock formation using mid-IR laser pulses carrying moderate energies.

Ultra-compact electro-optical switches based on long-range air-hole assisted subwavelength waveguides

Jian Li, XuGuang Huang, Qilong Tan, Wen Zhou, and Zanhui Chen

Doc ID: 240131 Received 08 May 2015; Accepted 29 Jun 2015; Posted 01 Jul 2015  View: PDF

Abstract: An ultra-compact electro-optical switch based on long-range air-hole assisted nanobeam waveguides with high extinction ratio, low insertion loss and high operation speed is proposed and investigated both analytically and numerically. The switching characteristic of the electro-optical switch is also addressed at three different resonant wavelengths. A modulation depth of 26.8dB and a small active region of 1.04µm at the wavelength of 1.597μm can be achieved. Such an active TE-mode device based on nanobeam waveguides provides a promising approach for highly effective electro-optical switches, and is beneficial for high-dense photonic integration.

Efficiency of dispersive wave generation in dual concentric core microstructured fiber

Daniele Modotto, Marco Andreana, Katarzyna Krupa, Gabriele Manili, Alessandro Tonello, Vincent COUDERC, Alain Barthelemy, Alexis Labruyere, Badr SHALABY, Phillippe Leproux, Stefan Wabnitz, Alejandro Aceves, and Umberto Minoni

Doc ID: 236666 Received 20 Mar 2015; Accepted 27 Jun 2015; Posted 01 Jul 2015  View: PDF

Abstract: We describe the generation of powerful dispersive waves that are observed when pumping a dual concentric core microstructured fiber by means of a sub-nanosecond laser emitting at the wavelength of 1064 nm. The presence of three zeros in the dispersion curve, their spectral separation from the pump wavelength, and the complex dynamics of solitons originated by the pump pulse break-up, all contribute to boost the amplitude of the dispersive wave on the long-wavelength side of the pump. The measured conversion efficiency towards the dispersive wave at 1548 nm is as high as 50%. Our experimental analysis of the output spectra is completed by the acquisition of the time delays of the different spectral components. Numerical simulations and an analytical perturbative analysis identify the central wavelength of the red-shifted pump solitons and the dispersion profile of the fiber as the key parameters for determining the efficiency of the dispersive wave generation process.

Localized and non-localized plasmon resonance enhanced light absorption in metal-insulator-metal nanostructures

Junpeng Guo, Wonkyu Kim, Blake Simpkins, James Long, Joshua Hendrickson, and Boyang Zhang

Doc ID: 236902 Received 25 Mar 2015; Accepted 26 Jun 2015; Posted 01 Jul 2015  View: PDF

Abstract: Multiple absorption bands in a metal-insulator-metal nanostructure are comprehensively investigated in the visible and near infrared regime. The metal-insulator-metal nanostructure consists of patterned gold squares with systematically varying size and period atop a thin aluminum nitride dielectric layer on a thick gold film. Both transverse-electric (TE) slab-waveguide mode and transverse-magnetic (TM) surface plasmon-polariton mode are excited in the structure. Grating coupling of the incident light into non-localized traveling waves is found from electromagnetic field patterns and from the linear dispersion of the absorption modes with period. A localized mode strengthens the near-IR absorption band for small square sizes, and the resonance shifts to red for large square sizes.

Graphical Analysis to Transient Absorption Spectra Using Phasor Approach

Yanzhou Zhou, Yun Zhang, yulei Bai, Hong Liu, Shuangli Ye, and Weichao Xu

Doc ID: 240526 Received 07 May 2015; Accepted 26 Jun 2015; Posted 01 Jul 2015  View: PDF

Abstract: Transient absorption spectroscopy is a powerful tool to study chemical dynamic processes. Several methods have been developed to transient absorption spectra data analysis, such as singular value decomposition and exponential fitting method. Here, we put forward an approach to transient absorption spectra data graphical analysis which is developed from Jameson’s phasor approach. It expands the research processes of Jameson’s phasor approach, and makes the visual analysis of different kinetic processes. The lifetime can be evaluated in phasor space without professional exponential fitting. The method is computationally efficient and straightforward to implement. The simulation result validates the effectiveness of the presented method to transient absorption spectra data analysis. The transient absorption phasor approach has the potential to simplify transient absorption spectra data analysis, and paving the way for the analysis of large data sets.

Passively mode-locked fiber laser based on non-CVD-thulium doped fiber

Dmitry Gaponov, Romain Dauliat, Dia Darwich, Tigran Mansuryan, Raphael Jamier, Stephan Grimm, Kay Schuster, and Philippe Roy

Doc ID: 233162 Received 23 Jan 2015; Accepted 24 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: The characterization of a thulium-doped fiber made from the new powder technology in the mode-locking regime is reported. High average output power of 185 mW at a repetition rate of 9 MHz was achieved directly from the oscillator, which is resulting in 21 nJ of pulse energy. The single-pulse operation regime was confirmed by careful numerical modeling of the laser cavity.

Femtosecond Source of Unbalanced Polarization-Entangled Photons

Katiuscia Cassemiro, Milrian Mendes, jorge fernandez, Antonio Coelho, Marcio Miranda, fernando parisio, Marco Bellini, and Daniel Barbosa

Doc ID: 241466 Received 26 May 2015; Accepted 23 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We characterize a polarization-entangled photon source based on femtosecond pulsed parametric down-conversion in a periodically-poled χ(2) medium. Employing a Sagnac interferometer, we prepared different quantum states aiming at future investigations in quantum information and on the foundations of quantum mechanics. In this work we therefore demonstrate the controlled generation of unbalanced entangled states, rather than the usual maximally-entangled ones, by tuning the polarization of the system’s pumping field.

Trichromatic phase manipulation of optical high-order sidebands in a photonic-crystal nanocavity embedded a single quantum dot

Li Jiahua, Rong Yu, wei wang, Chunling Ding, and Wu Ying

Doc ID: 240408 Received 08 May 2015; Accepted 22 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We explore the dependence of optical high-order sideband (HOS) spectra on the incident power and relative phase of a trichromatic driving field in a single-mode nanocavity coupled to a two-level quantum emitter beyond the weak-excitation approximation. With state-of-the-art experimental system parameters, it is found that the generated HOS can be enhanced significantly, compared with the bichromatic excitation. By varying the powers and phases of the trichromatic components, a few interesting phenomena such as enhancement, suppression, and quenching of HOS spectral lines can be achieved. For the phase dependence, it is the sum of relative phases of two sideband components of the trichromatic driving field to the central component that plays a crucial role in generating HOS. Optical HOS spectra exhibit remarkably different features once the sum phase is changed, but is kept unchanged regardless of the respective phases when the sum phase is fixed. The influences of the other system parameters including the emitter-cavity coupling strength and all kinds of relative frequency detunings on optical HOS generation are also discussed in detail. The underlying physical mechanism for optical HOS generation is presented. This investigation may find applications in optical frequency combs at low pump power level using cavity quantum electrodynamics.

Parametric oscillator in a Kerr medium: evolution of coherent states

Ricardo Roman, Jose Recamier, and Manuel Berrondo

Doc ID: 237908 Received 13 Apr 2015; Accepted 21 Jun 2015; Posted 25 Jun 2015  View: PDF

Abstract: We study the temporal evolution of a coherent state under the action of a parametric oscillator and a non-linear Kerr-like medium. We make use of the interaction picture representation and use an exact time evolution operator for the time independent part of the Hamiltonian. We approximate the interaction picture Hamiltonian in such a way as to make it a member of a Lie algebra. The corresponding time evolution operator behaves like a squeezing operator due to the temporal dependence of the oscillator’s frequency. We analyze the probability amplitude, the auto correlation function and the Husimi distribution function for different Hamiltonian parameters and we find a very good agreement between our approximate results and converged numerical calculations.

Real-time emission spectrum of a hybrid atom-optomechanical cavity

Imran Mirza

Doc ID: 237249 Received 31 Mar 2015; Accepted 18 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: We theoretically investigate the real-time emission spectrum of a two-level atom coupled to an optomechanical cavity (OMC). Using quantum trajectory approach we obtain the single-photon time-dependent spectrum in this hybrid system where the influence of a strong atom-cavity coupling and a strong optomechanical interaction are studied. We find a dressed state picture can explain the spectra by predicting the exact peak locations as well as the relative peak heights. In our analysis we also include the effect of mechanical losses (under weak mechanical damping limit) and single-photon loss through spontaneous emission from the two-level emitter.

Cherenkov radiation combined with complex Doppler effect in left-handed metamaterials

David Ziemkiewicz and Sylwia Zielińska-Raczyńska

Doc ID: 237970 Received 13 Apr 2015; Accepted 16 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: A unified analytical description of the Cherenkov and complex Doppler phenomena in a simple metamaterial model is presented. It is shown that a moving, monochromatic source generates radiation fields which exhibits features of both Doppler and Cherenkov effects. The presented theory explains many peculiar characteristics of the Cherenkov radiation in left-handed metamaterials such as the backward direction of power emission, the constant radiation angle and the lack of velocity threshold. The theoretical findings are confirmed by numerical simulations based on the Finite Difference Time Domain method.

Frequency comb generation by symmetry protected bound state in the continuum

Almas Sadreev and Konstantin Pichugin

Doc ID: 236408 Received 17 Mar 2015; Accepted 16 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: We study the dynamical response of two nonlinear microcavities symmetrically positioned relative to a photonic crystal waveguide. We find a domain in the space of frequency and amplitude of the injected light where all stationary solutions are unstable. In this domain scattered light carries multiple harmonics with equidistantly spaced frequencies (frequency comb effect). The instability is related to a symmetry protected bound state in the continuum whose response is singular as the amplitude of the injected wave tends to zero.

Perfectly Reflectionless Omnidirectional Absorbers and Electromagnetic Horizons

Kamalesh Sainath and Fernando Teixeira

Doc ID: 237129 Received 01 Apr 2015; Accepted 16 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: We demonstrate the existence of metamaterial blueprints describing, and fundamental limitations concerning, perfectly reflectionless omnidirectional electromagnetic absorbers (PR-OEMA). Previous attempts to define PR-OEMA blueprints have led to active (gain), rather than passive, media. We explain this fact and unveil new, distinct limitations of true PR-OEMA devices, including the appearance of an ``electromagnetic horizon' on physical solutions. As practical alternatives we introduce alternative OEMA blueprints corresponding to media that, while not reflectionless, are nonetheless effective in absorbing incident waves in a manner robust to incident wave diversity.

Microaxicon-generated photonic nanojets

Yuri Geints, Alexander Zemlyanov, and Ekaterina Panina

Doc ID: 238050 Received 14 Apr 2015; Accepted 11 Jun 2015; Posted 12 Jun 2015  View: PDF

Abstract: We report the calculations of optical radiation scattering at micron-sized conical-shape dielectric particles (microaxicons) with special attention given to the specific spatially localized near-field area constituting a photonic nanojet. By virtue of the finite-difference time-domain simulations we show for the first time that the photonic nanojet produced by a microaxicon of specific spatial orientation can exhibit extreme axial elongation up to ~25 (at fixed intensity level) while retaining high peak intensity and subwavelength transverse width.

Long Range Surface Plasmons in Multilayer Structures

Iterio Degli-Eredi, Aida Delfan, and John Sipe

Doc ID: 237720 Received 23 Apr 2015; Accepted 10 Jun 2015; Posted 15 Jun 2015  View: PDF

Abstract: We present a new strategy, based on a Fresnel coefficient pole analysis, for designing an asymmetric multilayer structure that supports long range surface plasmons (LRSP). We show that the electric field intensity in the metal layer of the multilayer structure can be reduced significantly, resulting in small absorption losses and LRSP propagation lengths up to 2 mm. With a view towards biosensing applications, we also present semi-analytic expressions for a standard surface sensing parameter in arbitrary planar resonant structures, and in particular show that for an asymmetric structure consisting of a gold film deposited on a multilayer of SiO2 and TiO2 a surface sensing parameter G=1.28 nm^-1 can be achieved.

Propagation of grating-coupled Surface Plasmon Polaritons and Cosine-Gauss Beams generation

Enrico Gazzola, Gianluca Ruffato, and Filippo Romanato

Doc ID: 235503 Received 04 Mar 2015; Accepted 09 Jun 2015; Posted 10 Jun 2015  View: PDF

Abstract: When a Surface Plasmon Polariton (SPP) is excited through a metallic grating in the conical mounting configuration, it propagates along a direction non-parallel to the grating Bragg vector. We will derive, under any possible coupling condition, the propagation direction as a function of experimental parameters, with particular attention to its relation with the azimuthal rotation angle. We will identify the conditions to achieve the maximum angular deflection with respect to the grating vector, also in relation to the grating geometry. Moreover, we will investigate the special configuration in which two SPP modes propagating towards different directions are simultaneously excited by the same light beam, suggesting to exploit this configuration to generate non-diffractive plasmonic beams (Cosine-Gauss Beams). The analytical treatment is supported by simulations with Chandezon’s method.

An analogue model for controllable Casimir radiation in a nonlinear cavity with amplitude-modulated pumping: Generation and quantum statistical properties

M H Naderi, ali motazedifard, and Rasoul Roknizadeh

Doc ID: 240661 Received 11 May 2015; Accepted 09 Jun 2015; Posted 10 Jun 2015  View: PDF

Abstract: We present and investigate an analogue model for a controllable photon generation via the dynamical Casimir effect (DCE) in a cavity containing a degenerate optical amplifier (OPA) which is pumped by an amplitude-modulated field. The time modulation of the pump field in the model OPA system is equivalent to a periodic modulation of the cavity length, which is responsible for the generation of the Casimir radiation. By taking into account the rapidly oscillating terms of the modulation frequency, the effects of the corresponding counter-rotating terms (CRTs) on the analogue Casimir radiation emerge clearly. We find that the mean number of generated photons and their quantum statistical properties exhibit oscillatory behaviours, which are controllable through the modulation frequency as an external control parameter. We also recognize a new phenomenon, the so-called “Anti-DCE ”, in which pair photons can be coherently annihilated due to the time-modulated pumping. We show that the Casimir radiation exhibits quadrature squeezing, photon bunching and super-Poissonian statistics which are controllable by modulation frequency. We also calculate the power spectrum of the intracavity light field. We find that the appearance of the side bands in the spectrum is due to the presence of the CRTs.

Analytical model for synchronous Raman amplification of high energy ultrashort pulses in optical fibers

Maxime Hardy, Michel Olivier, and Michel Piche

Doc ID: 237962 Received 15 Apr 2015; Accepted 04 Jun 2015; Posted 05 Jun 2015  View: PDF

Abstract: The amplification of ultrashort laser pulses to high energy and average power in optical fibers involves management of nonlinearity, gain bandwidth, dispersion and saturation. In this paper, we investigate the use of stimulated Raman scattering in optical fibers for high energy pulse amplification. The amplification of femtosecond pulses stretched to picosecond or even nanosecond durations by synchronized pump pulses is considered, assuming a carrier frequency difference close to the Raman gain peak frequency. An analytical solution for the pulse amplitude and phase profiles that includes the complete Raman gain spectrum plus self- and cross-phase modulation is given. To demonstrate the potential of this approach, we propose an amplifier-shifter setup with standard fibers to generate microjoule pulses with a duration around 100 fs at 1078 nm from a 250-fs nanojoule oscillator at 1030 nm. Simulations of an additional Raman amplifier stage with rod-type fibers resulted in pulse energies of a few millijoules, durations near 150 fs and peak powers larger than 10 GW after compression.

Metasurface-enhanced Optical Tamm States and Related Lasing Effect

Zhenqing Zhang, Yunhui Li, Young Sun, Hai Tao Jiang, Hai Lu, shaohua wang, and Hong Chen

Doc ID: 236201 Received 16 Mar 2015; Accepted 04 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: In this paper, meta-surface with electromagnetically-induced-relection-like (EIR-like) dispersion is introduced to enhance optical Tamm state (OTS) and related lasing effect. Numerical analysis and full-wave simulation confirm that this structure-induced EIR-like dispersion of meta-surface gives rise to the Q-factor of OTS. Consequently, enhanced lasing effect is also investigated when a four-level two-electron atomic system is introduced. The results show that the lasing threshold can almost be reduced to a half, with the enhancement of max emission intensity in the mean time. These features make the meta-surface-enhanced OTS structure promising for reducing the lasing threshold, enhancing the fluorescence, and so on.

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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