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Accepted papers to appear in an upcoming issue

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Quantum-Classical Access Networks with Embedded Optical Wireless Links

Osama Elmabrok, Mohsen Razavi, and Masoud Ghalaii

Doc ID: 302744 Received 19 Jul 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We examine the applicability of wireless indoor quantum key distribution (QKD) in hybrid quantum-classical networks. We propose practical configurations that would enable wireless access to such networks. The proposed setups would allow an indoor wireless user, equipped with a QKD-enabled mobile device, to communicate securely with a remote party on the other end of the access network. QKD signals, sent through wireless indoor channels, are combined with classical ones and sent over shared fiber links to the remote user. Dense wavelengthdivision multiplexing would enable the simultaneous transmission of quantum and classical signals over the same fiber. We consider the adverse effects of the background noise induced by Raman scattered light on the QKD receivers due to such an integration. In addition, we consider the loss and the background noise that arise from indoor environments. We consider a number of discrete and continuous variable QKD protocols and study their performance in different scenarios.

Investigation of graphene supported tunable asymmetrical THz metamaterials

Chenyuyi Shi, Xiaoyong He, Feng Liu, Fangting Lin, and hao zhang

Doc ID: 305035 Received 16 Aug 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: By integrating graphene layer with asymmetrical split-ring metamaterials (MMs) resonators, the tunable propagation properties have been investigated in the terahertz regime, including the effects of graphene Fermi level, structural parameters and operation frequencies. The results show that a sharp LC resonance can be observed at low frequency for the asymmetrical unit cell MMs structure, its Q-factor can reach more than 17.5. With the help of graphene layer, the optical response is modulated efficiently. For instance, if the Fermi level in the range of 0.01-0.3 eV, for the semiconductor MMs structure, the modulation depths (MD) of amplitude and frequency are 27.03% and 43.4%, respectively. In addition, the resonant curves of InSb MMs can be modulated by changing the temperature, the amplitude MD is 56.2% as the temperature changes in the range of 350-800 K. The Q-factor of InSb MMs structure is about 44.6. The results are helpful to design novel graphene based tunable THz devices, e.g. sensors, filters and modulators.

Design of Elliptical Few-Mode Fibers for Mode Coupling-Free Parametric Amplification

Cheng Guo, Zhenzhen Zhang, Ningbo Zhao, Liang Cui, Xiaoying Li, Jian Zhao, and Guifang Li

Doc ID: 307058 Received 18 Sep 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: In a few-mode optical parametric amplifier, which is based on intramode four-wave mixing, mode coupling between degenerate modes cause gain reduction and the signal gain varies depending on its mode pattern. Hence, it’s highly desirable to eliminate degenerate mode coupling in a few-mode parametric amplifier. We propose an elliptical-core dispersion shift few-mode fiber to suppress the mode coupling between degenerate modes. Simulation results show the fiber can be used for a four-mode parametric amplifier, with over 30 nm gain bandwidth across the C-band in a 300 m long fiber.

Damped Casimir radiation and photon correlation measurements

Ricardo Roman, Octavio Sánchez, and carlos gonzalez gutierrez

Doc ID: 307170 Received 14 Sep 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: An effective toy model for an ideal one-dimensional nonstationary cavity is taken to be the starting point to derive a fitting markovian master equation for the corresponding leaky cavity. In the regime where the generation of photons via the dynamical Casimir effect is bounded, the master equation thus constructed allows us to investigate the effects of decoherence on the average number of Casimir photons and their quantum fluctuations through the second-order correlation function.

Multilayer graphene based optical bistability

Vahid Ahmadi and mehdi Sadeghi

Doc ID: 309708 Received 23 Oct 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: In this paper, optical bistability of multilayer graphene structures is proposed and investigated. Here, results show that in spite of reduction of the Fermi level, we have optical bistability behavior in multilayer graphene structures in comparison to single layer one. Also, the hysteresis width and threshold values are adjustable. It should be mentioned that the layer numbers can be increased to specific numbers because of large loss and low on-state transmission due to electron-phonon relaxation time. Combination of the Fermi level and layer numbers provide us appropriate tuning to achieve desirable hysteresis width, threshold values and On-state to Off-state transmission ratio. Considering typical electron-phonon relaxation time of 1 ps, silicon as dielectric medium and the Fermi level about 0.7 eV, a structure with 4 graphene layers gives us On-state to Off-state transmission ratio of about 11.48, On-state transmission of 0.31 and hysteresis width of 1.24 MV/m which seems to be favorable at 1 terahertz and normal incidence condition. Our results support using multilayer graphene structures for future optical bistability based low power and tunable optical devices.

Implementation of a Single-Shot Receiver for Quaternary Phase-Shift Keyed Coherent States

Matthew DiMario, Ezequiel Carrasco, Richard Jackson, and Francisco Becerra Chavez

Doc ID: 310150 Received 30 Oct 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: Non-Gaussian receivers that achieve discrimination errors below the Quantum Noise Limit (QNL) are an important tool in communication. We experimentally demonstrate a strategy proposed by Izumi et al. to discriminate between quaternary phase-shift keyed (QPSK) coherent states that is based on simultaneously testing multiple hypotheses within a single-shot measurement. The strategy uses displacement operations and single photon counting without the need for any feedback operations, and its simplicity makes it in principle compatible with high-bandwidth communications. Our implementation uses a polarization-based setup consisting of only waveplates, beam splitters and single photon counters. This setup is inherently stable and ideal for the investigation of single-shot measurements with multi-hypothesis testing. Our implementation allows for a high degree of control over the displacement operations, which are optimized to minimize the probability of error given experimental imperfections. We investigate how the realistic experimental parameters, such as visibility of the displacement operations, influence the error probability and identify what would be required in our implementation to to outperform an ideal Heterodyne measurement operating at the QNL. Our result serves as a benchmark for realistic implementations of simple QPSK discrimination strategies that do not rely on feedback, number resolving detectors, or active phase stabilization.

Carrier-envelope phase stability of a polarization-encoded chirped pulse Ti:Sapphire amplifier

Roland Nagymihály, Huabao Cao, Péter Jójárt, Mikhail Kalashnikov, Adam Borzsonyi, Vladimir Chvykov, Roland Flender, Mate Kovacs, and Karoly Osvay

Doc ID: 312631 Received 03 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: The scheme of polarization-encoded chirped pulse amplification (PE-CPA) reduces the gain narrowing effect in Ti:Sapphire (Ti:Sa) amplifiers by utilizing both crystal axes of Ti:Sa. Hence, the carrier-envelope phase (CEP) of a PE-CPA pulse is originating from two othogonal polarization directions. The CEP stability of PE-CPA pulses was investigated for various amplification conditions by varying the pump pulse energy. The CEP stability is directly compared to the conventional CPA scheme under the same laser parameters. A quasi-common path interferometer was realized inside a four-pass amplifier stage, ensuring exceptional geometrical path length stability and high spectral phase sensitivity. The spectral phase noise of PE-CPA pulses showed a minor increase of 4 mrad compared to the conventional scheme, while at unsaturated amplification of a net gain of 13 it revealed a CEP stability better than 63 mrad.

Role of short-range order in manipulating light absorption in disordered media

Mengqi Liu, Changying Zhao, Boxiang Wang, and Xing Fang

Doc ID: 312645 Received 03 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: Structural correlations have a significant effect on light propagation in disordered media. We numerically investigate the role of short-range order in light absorption in thin films with disordered nanoholes. Two types of disordered distributions, including stealthy hyperuniform (SHU) and hard disk (HD) patterns with different degrees of short-range order, are studied. We find that Bragg scattering induced by short-range order results in the appearance of a gradually sharper absorption peak with the increasing of the degrees of short-range order (χ, ø). A physical model is proposed to calculate the in-plane angularly differential scattering cross section dσ*/d θ of thin-film nanostructures with consideration of structure factor S(q). Results reveal that higher level of short-range order can enhance in-plane Bragg scattering in certain wavelengths and directions corresponding to rich and sharp peaks in structure factor S(q), which can further modify morphology-dependent-like resonances of an individual scatterer, leading to improvement of absorptivity in thin films. Besides, the comparison results show that SHU structures exhibit better integrated absorption (IA) enhancement than both HD and periodic structures. And there is a transition of local-order phase between hexagonal lattice and square lattice, leading to an optimal absorption performance when χ is around 0.5 of interest. The present study paves a way in controlling light absorption and scattering using novel disordered nanostructures.

Two-stream theory of light propagation in amplifying media

Vadim Markel

Doc ID: 312781 Received 06 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: Two-stream approximation to the radiative transport equation (RTE) is a convenient exactly solvable model that allows one to analyze propagation of light in amplifying media. In spite of neglecting the phase and the interference effects, this model describes the same phenomena as Maxwell's equation: electromagnetic resonances, onset of lasing and onset of instabilities. An important added bonus of the RTE description is that it provides for a simple and unambiguous test of physicality of stationary solutions. In the case of Maxwell's equations, it is not always obvious or easy to determine whether certain stationary (in particular, monochromatic) solutions are physical. In the case of RTE, the specific intensity of unphysical stationary solutions becomes negative for some subset of its arguments. In the paper, stationary and time-dependent solutions to the two-stream model are analyzed. It is shown that the conditions for stationary lasing and for emergence of instabilities depend only on the geometry of the sample and the strength of amplification but not on the intensity of incident light.

High-speed time-domain balanced homodyne detector for nanosecond optical field applications

shanna du, Zongyang Li, wenyuan liu, xuyang wang, and Yongmin Li

Doc ID: 312859 Received 06 Nov 2017; Accepted 08 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We present a high-speed time-domain shot-noise–limited balanced homodyne detector that is suitable for the detection of the quantum states of nanosecond pulsed optical fields. The detector can detect the quantum noise of individual nanosecond optical pulses at a repetition rate of 40 MHz and achieve a signal-to-noise ratio of above 13 dB. The stability of the detector is characterized via an Allan variance measurement, and superior stability is observed. The detector is especially applicable in the fields of quantum optics and quantum information, where high-speed time-domain detection of nanosecond pulsed optical field quadratures are required.

Fast production of rubidium Bose-Einstein condensate in a dimple trap

Dizhou Xie, Dongyue Wang, Wei Gou, Wenhao Bu, and Bo Yan

Doc ID: 314865 Received 04 Dec 2017; Accepted 05 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We reported a simple scheme of producing Bose-Einstein condensate (BEC) in a dimple trap. Starting from a regular magneto-optical trap (MOT), we apply a temporal dark MOT to increase the atom density, and directly load atoms into a crossed dipole trap. In order to make the trap frequency relative high at the end of evaporation, a tight dimple is added. Such scheme ensure relative high trap volume for loading atoms and high trap frequency for evaporative cooling. The BEC phase transition is observed after $12s$ evaporation. Further more, we demonstrated the manipulation of the hyperfine states with a Raman coupling, which is very useful for studying the many-body physics via the Ramsey or spin echo spectroscopy.

Tuning Parametric Processes in Semiconductor Diode Lasers

Nima Zareian, Amr Helmy, and Dongpeng Kang

Doc ID: 315664 Received 14 Dec 2017; Accepted 04 Jan 2018; Posted 09 Jan 2018  View: PDF

Abstract: We present GaAs/AlGaAs semiconductor lasers in which second order nonlinearities are phase-matched for efficient second-order nonlinear conversion. A comprehensive study of difference frequency generation (DFG) is presented and the process is characterized for tuning, efficiency, and tolerances. External nonlinear conversion efficiency of 1.84e-2 /W/cm2 is measured for the DFG process. The effect of carrier injection and temperature variation on DFG wavelength are studied and the two effects are de-convolved for better understanding of carrier effects on nonlinear conversion. A wide DFG tuning range for the device operation is experimentally demonstrated where the idler wavelength can be tuned more than 30nm for every 1nm span of the pump wavelength.

Coupling coefficient in antiguided coupling: magnitude and sign control

Zihe Gao, Dominic Siriani, and Kent Choquette

Doc ID: 309251 Received 16 Oct 2017; Accepted 04 Jan 2018; Posted 05 Jan 2018  View: PDF

Abstract: The coupling coefficient between two passive antiguided waveguides is investigated. A novel approach for identifying the in-phase and out-of-phase coupled modes in an antiguided system through the dispersion curves is described. The coupling coefficient between these modes is found to be real, and its sign and magnitude are influenced by the thickness and refractive index of the inter-element region between the two waveguide cores. The change of sign of the coupling coefficient is verified by a refocusing phenomenon apparent in numerical simulations of a two-section antiguided waveguide. In addition, design points have been identified where the coupling coefficient is relatively invariant against the perturbation of both inter-element separation and inter-element refractive index, benefiting the fabrication tolerance.

Anomalous scaling laws of hyperbolic metamaterials in a tubular geometry

Shi-Wei Tang, Yangfu Fang, Lei Zhou, Zhaowei Liu, and Yongfeng Mei

Doc ID: 309225 Received 16 Oct 2017; Accepted 30 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: Hyperbolic Metamaterials (HMM) can be used to control light propagations in emerging meta-devices and thus lead to various functionalities (e.g. hyperlens and cloaking devices). Here we propose a kind of exotic tubular cavities by using multilayered HMM, which contrasts with traditional materials with elliptical dispersion. In such tubular microcavity, the calculations reveal that it has anomalous scaling laws, such as the higher-order resonance mode oscillates at a longer wavelength and the resonant wavelengths hold their positions with changing the tube wall thickness and diameter. These findings can help the understanding of tubular metamaterials and could inspire interesting optical experiments and meta-devices.

Revealing the physical mechanisms behind large field enhancement in hybrid spoof plasmonic systems

Yao Huang, Jingjing Zhang, Tie Jun Cui, Zhen Liao, and Dao Hua ZHANG

Doc ID: 309672 Received 20 Oct 2017; Accepted 30 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We compare different spoof LSP schemes for increasing the field enhancement in subwavelength regime. Based on the mechanisms of three differently widely used corrugated metallic disk structures, we compare three widely-used corrugated disks and propose a nonconcentric spiral shaped metallic disk structure which not only maximizes the electromagnetic field confinement but also effectively reduces the radiation loss. The performance can be further improved by adopting a hybrid system consisting of two closely spaced nonconcentric spiral structures. We show that such a dimer of nonconcentric spiral disk produces significant field enhancement compared with the previously discussed structures. Our study provides perceptive guideline for potential applications like plasmonic sensors and antennas associated with LSPs in the microwave and terahertz frequencies.

Cross–phase–modulation–induced temporal reflection and waveguiding of optical pulses

Brent Plansinis, Govind Agrawal, and William Donaldson

Doc ID: 309753 Received 23 Oct 2017; Accepted 28 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: Cross-phase modulation (XPM) is commonly viewed as a nonlinear process that chirps a probe pulse and modifies its spectrum when an intense pump pulse overlaps with it. Here we present an alternative view of XPM in which the pump pulse creates a moving refractive-index boundary that splits the probe pulse into two parts with distinct optical spectra through temporal reflection and refraction inside a dispersive nonlinear medium. The probe even undergoes a temporal version of total internal reflection for sufficiently intense pump pulses, a phenomenon that can be exploited for making temporal waveguides. We investigate the practical conditions under which XPM can be exploited for temporal reflection and waveguiding. The width and shape of pump pulses as well as the nature of medium dispersion at the pump and probe wavelength (normal versus anomalous) play important roles. The super-Gaussian shape of a pump pulse is particularly helpful because of the relatively sharp edges of the super-Gaussian shape. When the pump wavelength lies in the anomalous-dispersion regime, the pump pulse can form a soliton, whose unique properties can be exploited to advantage. We also discuss a potential application of XPM-induced temporal waveguides for compensating timing jitter.

Virtual-State Spectroscopy with Frequency-Tailored Intense Entangled Beams

Jiri Svozilík, Jan Perina, and Roberto Leon

Doc ID: 308991 Received 11 Oct 2017; Accepted 28 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: In this contribution we analyze virtual-state spectroscopy --- a uniquetool for extracting information about the virtual states thatcontribute to the two-photon excitation of an absorbing medium--- as implemented by means of intense entangled beams with tunable spectral correlations. We provide a thorough description of allcontributing terms (classical and quantum) in the two-photonabsorption signal, as well as the limits imposed by the power ofthe pump that produces the entangled beams on the observability ofthe spectral lines of the virtual transitions. We find thatvirtual-state spectroscopy may be implemented with entangledtwin beams carrying up to $10^4$ photon pairs. This implies that, inprinciple, one might be able to detect two-photon absorptionsignals up to four orders of magnitude larger than previouslyreported, thus paving the way towards the first experimentalrealization of the virtual-state spectroscopy technique.

Far-field pattern formation by manipulating the topological charges of square-shaped optical vortex lattices

Lyubomir Stoyanov, Georgi Maleshkov, Maya Zhekova, Ivan Stefanov, Dragomir Neshev, Gerhard Paulus, and Alexander Dreischuh

Doc ID: 312873 Received 06 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: In this work we demonstrate experimentally the formation of ten different structures consisting of bright beams with flat phase fronts in the focus of a lens (i.e. in the artificial far field). The used basic structure is a large, stable, square-shaped optical vortex (OV) array composed of vortices with alternating topological charges. The topological charges of one individual OV, of a sub-array of OVs, or of the complete OV lattice were erased/doubled in the cases of perfect superposition (on-site alignment) or are manipulated in phase in the cases of an offset between the vortices (off-site alignment). A dramatic reshaping of the beam is observed in the far-field and shown to be in excellent agreement with numerical simulations.

Low-loss and high-performance mid-infrared plasmon-phonon in Graphene-Hexagonal boron nitride waveguide

Yaser Hajati, Mohammad Sabaeian, and Zeinab Zanbouri

Doc ID: 313204 Received 13 Nov 2017; Accepted 27 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: In this article, we propose a class of high-performance and low-loss waveguide by exploiting the hybridization of the plasmon-phonon modes through coupling graphene with hexagonal boron nitride (hBN). It is found that inserting an ultra-thin hBN layer with hyperbolicity behavior between graphene and a thin low-index substrate leads to squeezing light into hBN, enabling low-loss light propagation as compared with traditional graphene/substrate plasmonic waveguide. Furthermore, the results show that by choosing appropriate values for physical parameters of proposed waveguide as well as chemical potential of graphene, low-loss and high-performance optical plasmon-phonon mode in the mid-infrared range can be achieved simultaneously. In particular, by increasing the chemical potential from 0.2 to 1 eV, 12 and 6 fold enhancement for propagation length (Lm) and figure of merit (FOM), respectively, is achieved with the optimized proposed waveguide. The results presented here are very helpful for designing the low-loss nanophotonic devices.

Numerical modelling of the coupling efficiency of single quantum emitters in photonic-crystal waveguides

Alisa Javadi, Sahand Mahmoodian, Immo Soellner, and Peter Lodahl

Doc ID: 308958 Received 11 Oct 2017; Accepted 26 Dec 2017; Posted 09 Jan 2018  View: PDF

Abstract: Planar photonic nanostructures have recently attracted a great deal of attention for quantum optics applications. In this article, we carry out full 3D numerical simulations to fully account for all radiation channels and thereby quantify the coupling efficiency of a quantum emitter embedded in a photonic-crystal waveguide. We determine the leakage from the quantum emitter to the surrounding environment and study its spectral and spatial dependence. The spatial maps of the coupling efficiency, the $\beta$-factor, reveal that even for moderately slow light, near-unity $\beta$-factor is achievable and the $\beta$-factor is remarkably robust to the position of the emitter in the waveguide.

Stabilizing multi-lasers with a tunable high finesse transfer cavity for single atom Rydberg excitation

Yong Zeng, Kun Wang, Yang Liu, Xiaodong He, Min LIU, Peng XU, Jin Wang, and Mingsheng Zhan

Doc ID: 305466 Received 05 Sep 2017; Accepted 24 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We demonstrate a method to simultaneously suppress the linewidths and stabilize the long-term frequency drifts of both 780 nm and 960 nm lasers to 10 kHz level. We first use an Iodine frequency stabilization laser as a frequency reference to stabilize the length of a tunable high finesse transfer cavity (THFTC). Then two slave lasers of 780 nm and 960 nm are locked this THFTC. In this way, the linewidths of slave lasers are suppressed to the order of 10 kHz which are measured by delayed self-heterodyne measurements. Meanwhile the long term frequency drifts are stabilized to be less than 22 kHz for 10 hours. With the locked lasers, we realize the coherent Rydberg excitation of single ⁸⁷Rb atom and keep the exciting stable and repeatable for 10 hours, which is essential for Rydberg-mediated single-atom quantum information processing. This multi-laser frequency stabilization and transfer method can also be used in other high resolution experiments in atomic physics, precision metrology and molecular spectroscopy.

Phase matched harmonic generation in gas-filled waveguides in the vicinity of a multi-photon resonance

Patric Ackermann, Xavier Laforgue Marin, Mario Hilbig, Maximilian Schilder, and Thomas Halfmann

Doc ID: 309626 Received 23 Oct 2017; Accepted 23 Dec 2017; Posted 03 Jan 2018  View: PDF

Abstract: We investigate phase matched harmonic generation of ultrashort (ps) laser pulses, tuned in the vicinity of a five-photon resonance in Argon, confined in a hollow-core optical waveguide. This combines resonance enhancements and tight spatial confinement to increase the conversion efficiency towards vacuum-ultraviolet radiation pulses. We demonstrate, that appropriate choice of the gas pressure maintains optimal phase matching conditions also in the presence of inevitable dynamic level shifts at high intensities. Moreover, we reveal the considerable contribution of higher-order transversal waveguide modes to the total conversion efficiency, and investigate the role of cascading frequency conversion processes. Finally, we study additional signal enhancements by buffer gas admixtures. The experimental data are compared with numerical simulations, taking higher transversal waveguide modes and cascade frequency conversion into account, identifying also the potential of quasi-phase-matching by polarization mode beating. Our investigations show, that proper choice of experimental parameters enables significant resonance enhancements in the conversion efficiency of harmonic generation.

Optical nonreciprocity via nonlinear Jaynes-Cummings model ina gain microcavity

Anshou Zheng, Yunfei Ma, and Tieping Li

Doc ID: 309918 Received 24 Oct 2017; Accepted 22 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: Optical nonreciprocal devices are essential to quantum information processing and communication. We pro-posed a scheme for optical nonreciprocity via nonlinear Jaynes-Cummings model in a gain cavity. In addition,the gain cavity is coupled to two fibers with different coupling strengths. In the scheme, the nonlinearity, whichis induced by the interaction between a two-level quantum emitter and the cavity field, is enhanced by thecavity gain. Our calculations show that the non-lossy optical nonreciprocity is achievable with high isolationratio in proper parameter range. Especially, the analytic method further shows the reciprocity broken by thecombination of the asymmetric coupling and enhanced nonlinearity.

Semiconductor ring laser with filtered optical feedback: traveling wave description and experimental validation

Mindaugas Radziunas, Mulham Khoder, Vasile Tronciu, Jan Danckaert, and Guy Verschaffelt

Doc ID: 308967 Received 10 Oct 2017; Accepted 22 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: We study experimentally and theoretically a semiconductor ring laser with four filtering channels providing filtered delayed optical feedback. To describe and analyze the wavelength selection and tuning in this device, we exploit the traveling-wave model determining the evolution of optical fields and carrier density along the ring cavity and filtering branches. The numerical results agree with the experimental observations: we can reproduce the wavelength tuning, the multiple wavelength emission, and the wavelength switching speed measured in these devices. The traveling-wave model allows us to study in detail the effect of the different laser parameters and can be useful for designing the future devices.

Dynamics of light-induced thermomechanical mirror deformations in high-finesse Fabry-Perot microresonators

kumarasiri konthasinghe, Juan Gomez Velez, Manoj Peiris, Yamil Nieves, Luisa Profeta, and Andreas Muller

Doc ID: 308567 Received 04 Oct 2017; Accepted 22 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: Light recirculating inside an optical resonator can spontaneously trigger persistent cyclical thermomechanical mirror deformations. We have observed and characterized the dynamics of such deformations in high-finesse Fabry-Perot microcavities built following three distinct designs. The designs differed in form factor and confinement geometry, incorporating either (A) two nominally planar bulk mirrors, (B) one planar and one micro-concave bulk mirror, and (C) one micro-concave bulk mirror and one micro-concave mirror at the tip of an optical fiber. For all cases, the cavity transmission exhibited bistability and high-frequency (MHz) high-amplitude pulsations for input powers greater than 10 mW at a cavity finesse of 30 000. A theoretical analysis reveals that these pulsations are the result of the competition between photothermal expansion and photothermal refraction in the mirror coatings that induces "slow-fast" dynamics. We model these dynamics for the three different cavities and show that their varying cycle duration and period is consistent with light-induced heating and heat dissipation conforming to the cavity mode spot size and the mechanical mirror support structure.

Efficient hyperentanglement purification using a $\Lambda$ system coupled with a whispering-gallery-mode microresonator

Tie-Jun Wang, Chang Shi, and De-Zhi Chen

Doc ID: 308783 Received 10 Oct 2017; Accepted 21 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: Entanglment purification is of great importance in long distance quantum communications and distributed quantum computations. Here we present an efficient scheme for the hyperentanglement purification of two-photon system, by using high-dimensional mode-check measurement device which is composed of $\Lambda$-type atoms and a quantized whispering-gallery mode (WGM) microresonators. We use the 4-dimensional hyperentanglement distilling operation as an example to explain the main idea of our scheme. High-dimensional mode-checking measurement operation and the conventional 2-dimensional parity-checking can be both used to pick up a high-fidelity set from nonlocal hyperentangled resources, but the conventional parity-checking operation can only implement state-selection within a single degree of freedom (DOF) while high-dimensional mode-checking operation can perform state-selection in crossing area of two DOFs. Therefore, the present high-dimensional mode-checking measurement can achieve a better performance than the conventional parity-checking one. Compared with the conventional hyperentanglement purification schemes in which the two-dimensional parity-checking measurement is exploited to correct the bit-flip errors, our scheme can provide quantum communication more robust against the decoherence in noisy channels with a wider distillation range and a higher fidelity by exploring higher dimensional mode-check measurement. The implementation of our hyperentanglement purification is assisted by nitrogen-vacancy centers in optical microresonators, which could be achieved with current techniques.

Influence of an external magnetic field in the two-photon absorptioncoefficient of magnetite nanoparticles in colloids and thin films

Daniel Garcia Espinosa, Cristiano Oliveira, and Antonio Martins Figueiredo Neto

Doc ID: 309692 Received 23 Oct 2017; Accepted 20 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: The Z-Scan nonlinear optical and the Small-Angle X-Ray Scattering(SAXS) techniques are used to investigate the structure and nonlinearoptical properties of magnetite nanoparticles dispersed in a colloidand trapped in thin films. The nonlinear refractive index (n2)and the two-photon absorption coefficient (β) were measuredas a function of the intensity of an external applied magnetic fieldH. Different relative orientations of the field with respect tothe light-polarization direction were investigated. When the externalmagnetic field is applied to the colloidal sample (H parallel tothe light-polarization direction), the two-photon absorption coefficientincreases with the field, ranging from β=1.5 cm/GW(without field) to β=2.4 cm/GW (2700 Oe).For the field direction perpendicular to the light polarization direction,β decreases to β=1.0 cm/GW (2700 Oe)and after remains constant. These values evidence a two-photon absorption anisotropy in magnetite, and allowed us to evaluate some elements of the third-order nonlinear optical susceptibility tensorχ(³). The SAXS experiments revealed that when the field isapplied, small linear aggregates are formed in the direction of H.

Second Harmonic Generation in PPLN waveguides with stitching errors

Maxim Neradovskiy, elizaveta neradovskaia, Dmitry Chezganov, Evgeny Vlasov, Vladimir Shur, Hervé Tronche, Florent Doutre, Getachew ayenew, Pascal Baldi, Marc Micheli, and Carlos Montes

Doc ID: 308310 Received 10 Oct 2017; Accepted 15 Dec 2017; Posted 18 Dec 2017  View: PDF

Abstract: Depending on the chosen fabrication process, nonlinear waveguides realized inperiodically oriented material such as Periodic Poled Lithium Niobate (PPLN)can present different fabrication errors. In this paper we present a detailednumerical study of the impact on the nonlinear performancesof one or severalstitching errors occurring during the realization of the periodic domainsby e-beam writing.This study shows that contrarily to what was expected, a si ngle finite stitching error does notsimply decrease the nonlinear efficiency, but splits the Second Harmonic (SH) signal into a doublepeak spectrum, where the position of the peaks and their width at half maximum depend not only onthe poling period, the total length of the grating, and the waveguide parameters but also on theamplitude and the position of the defect. The numerical results are confirmed by Second HarmonicGeneration (SHG) experiments performed in PPLN waveguides obtained by Soft Proton Exchange andwhere the nonlinear grating was composed of one to four e-beam written 1.5 mm long PPLN sectionsbetween which important stitching error can occur. In this case the spectrum can be quite complicated.It is worth noting that similar errors (domains merging or missing domains)can occur also in e-field poling process but they are randomly distributed along the propagation path.Therefore this study is a first attempt to take them into account to explain experimental resultsand indicate the steps that have to be taken to improve the quality of the components.

Supercontinuum generation in organic liquid-liquid core-cladding photonic crystal fiber in visible and near infrared regions

rasoul raei

Doc ID: 305293 Received 31 Aug 2017; Accepted 15 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: In this paper, we propose liquid core-cladding photonic crystal fiber (PCF), which engineered with different available organic optofluidics to generate supercontinuum in visible and near infrared (NIR) regime by using symmetrized split-step Fourier method (S-SSFM). Simulations reveal, in response to launching 50 fs input pulses of 10 kW peak power, centered about λ0=1032 and 1560 nm, into 10 mm long liquid core-cladding PCF, maximum 2 μm supercontinua from 500 to 2500 nm can be achieved. Our numerical study is important for the novel field of visible and near-IR supercontinuum generation in liquid-core optical fibers.

An perturbation-iteration method for multi-peak solitons in nonlocal nonlinear media

Weiyi Hong, B Tian, Rui Li, Qi Guo, and Wei Hu

Doc ID: 306447 Received 05 Sep 2017; Accepted 13 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: An perturbation-iteration method is developed for the computation of the Hermite-Gauss-like solitons with arbitrary peak numbers in nonlocal nonlinear media. This method is based on the perturbed model of the Schrödinger equation for the harmonic oscillator, in which the minimum perturbation is obtained by the iteration. This method takes a few tens of iteration loops to achieve enough high accuracy, and never involves the initial condition problem. The method we developed might also be extended to the numerical integration of the Schrödinger equations in any type of potentials.

High-gain, Low threshold and Small footprint Optical Parametric Amplifier for Photonic Integrated Circuits

Shatrughna Kumar and Mrinal Sen

Doc ID: 312553 Received 06 Nov 2017; Accepted 13 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: A new model of an optical parametric amplifier is proposed based on silicon-slab slotted photonic crystal waveguide (SPCW). The slot is considered to be filled with silicon nanocrystal material (SiNC/SiO2) having a high Kerr nonlinearity. The extreme optical confinement (spatial and temporal) of the SPCW has enhanced the optical nonlinearity and, thus, a high parametric gain is attained in a small length of the waveguide. Further, for analyses of pulse propagation, the coupled nonlinear Schrodinger’s equations have been modified to incorporate the enhancements in the linear and the nonlinear coefficients due to the slow-light effect. Simulations have been performed both on the high group index region and the low dispersion regions of the guided band. The simulations on the high group index region, centered at ≈ 1584 nm, depicts a 22.6 dB parametric gain and a 20.9 dB conversionefficiency at a waveguide length of 152 μm; with an effective pump power and peak input signal power of 700 mW and 0.25 mW respectively. The pulsating signal, with a pulse width of 5 ps, also experienced a negligible deterioration in their pulse shapes in this length of the SPCW. On the other hand, the simulations on the region of negligible dispersion, centered at 1530 nm, have produced an over 10 dB parametric gain and conversionefficiency through a long range of wavelengths, i.e. 1490 − 1568 nm, which covers half of the S-band and the complete C-band of the optical communication windows. The significant gain at a micron scale lengthof the waveguide is expected to advance the possibility of on-chip integration of high-speed all-optical amplifier in photonic integrated circuits.

Experimental simulation of a decohering Schrödinger's cat state in wave optics

Makoto Takeuchi, Keisuke Nishimura, and Takahiro Kuga

Doc ID: 313504 Received 15 Nov 2017; Accepted 13 Dec 2017; Posted 15 Dec 2017  View: PDF

Abstract: The study of decoherence properties improves our understanding of the fundamental principles of quantum mechanics and advances the study of quantum information processing.Herein, we report a wave-optical experiment that can simulate the decoherence process of a Schrödinger's cat state (SCS) by photon loss.The method is based on an analogy between image rotation in wave optics and a beam splitter in quantum optics.Experimental results show that the SCS rapidly decays into a statistical mixture of two Gaussian distributions with approximately 10 % photon loss.This behavior can be well described within the framework of quantum optics.

Holograms for power-efficient excitation of optical surface waves

Anton Ignatov and Alexander Merzlikin

Doc ID: 305618 Received 24 Aug 2017; Accepted 11 Dec 2017; Posted 13 Dec 2017  View: PDF

Abstract: A method for effective excitation of optical surface waves based on holography principles has been proposed. For a particular example of excitation of a plasmonic wave in a dielectric layer on metal the efficiency of proposed volume holograms in the dielectric layer has been analyzed in comparison with optimized periodic gratings in the dielectric layer. Conditions when the holograms are considerably more efficient than the gratings have been found out. In addition, holograms recorded in two iterations have been proposed and studied. Such holograms are substantially more efficient than the optimized periodic gratings for all incidence angles of an exciting Gaussian beam. The proposed method is universal: it can be extended for efficient excitation of different types of optical surface waves and optical waveguide modes.

Vortex solitons produced in spatially modulated linear and nonlinear refractive index waveguides

Siliu Xu, Milivoj Belic, Dong-Ping Cai, li xue, jiaxi cheng, and Jun-Rong He

Doc ID: 304260 Received 08 Aug 2017; Accepted 25 Oct 2017; Posted 04 Jan 2018  View: PDF

Abstract: We discuss analytical localized soliton solutions to the generalized nonautonomous nonlinear Schrödinger equation (NLSE) in waveguides featuring transverse modulation of both the linear and nonlinear refractive indices. We utilized the similarity transformation technique to obtain these solutions. Constraints on the linear and nonlinear refractive indices are presented at the same distance. It turns out that the generalized nonautonomous NLSE with space-dependent coefficients can be reduced to the stationary NLSE . Various shapes of exact vortex soliton solutions are studied theoretically and analytically. Finally, the stability analysis of the solutions is discussed numerically. Our findings address an alternative way for the realization of stable vortex solitons with higher topological charges and the radial quantum numbers.

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