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Accepted papers to appear in an upcoming issue

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Review of recent progress on single-frequency fiber lasers

Shijie Fu, Wei Shi, Yan Feng, Zhongmin Yang, lei zhang, Shanhui Xu, Xiushan Zhu, Robert Norwood, and Nasser Peyghambarian

Doc ID: 277898 Received 30 Sep 2016; Accepted 19 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: Single-frequency fiber lasers have drawn intense attention for their extensive applications from high-resolution spectroscopy and gravitational wave detection to materials processing due to the outstanding properties of low noise, narrow linewidth and the resulting long coherence length. In this paper, the recent advances of single-frequency fiber oscillators and amplifiers are briefly reviewed in the broad wavelength region of 1~3 μm. Performance improvements in laser noise and linewidth are addressed with the newly developed physical mechanisms. The solution to achieving higher power/energy is also discussed, accompanied by the start-of-the-art results achieved to date.

Control of dynamics in loss-modulated erbium doped fiber ring laser

R. Vijaya and Gyanendra Kumar

Doc ID: 280461 Received 08 Nov 2016; Accepted 18 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: Experimental investigation of the time-domain dynamics of an erbium doped fiber ring laser (EDFRL) by the loss modulation technique is carried out using an intensity modulator in the ring cavity, for the modulation frequency range of 1-60 kHz. By changing the four control parameters of pumping ratio, modulation frequency, modulation index, and modulator bias voltage, the laser dynamics can be modified all the way from period-1 to the chaotic regime. The presence of period-1, period-2, period-4, higher periods and chaos confirm that the chaos is achieved through period-doubling route. However, period-3 and period-6 are also obtained through other routes for certain parametric choices. The effect of pumping ratio is also discussed. A higher value of pumping ratio requires a higher modulating signal amplitude to push the laser into the chaotic regime till the second laser threshold. Besides this, the chaotic regimes for the higher pumping ratio are wider and shifted towards higher frequencies. Calculations done with the appropriate theoretical model provide a suitable handle on the parameters and help in emphasizing the control possible in this multi-parameter dynamical system.

Tunable photon statistics in a non-Hermitian system

sama shakeri, Mohammad-Hossein Zandi, and Alireza Bahrampour

Doc ID: 273533 Received 10 Aug 2016; Accepted 17 Jan 2017; Posted 19 Jan 2017  View: PDF

Abstract: We propose a PT-symmetric system using of recently proposed non-Hermitian model for resonant cavities coupled by a chiral mirror. Our model consists of a nonlinear cavity coupled to an optomechanical system by chiral mirror with both cavities being driven coherently. We consider the photon statistics and compute the optimal conditions of strong antibunching in non-Hermitian system. The results show, this model presented the best control of the strong antibunching effect by tuning the non-reciprocal coupling strength between the cavities, the strength ratio between two fields and nonlinearity strength which Hermitian system can not access it.

Influence of thermal fluctuations on optical properties of liquid metacrystals

Alexander Zharov, Alexander Zharov, and Nina Zharova

Doc ID: 282023 Received 01 Dec 2016; Accepted 14 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: We analyse the influence of thermal disordering of meta-atoms on the electromagnetic properties of liquid metacrystals (LMCs) which comprise of ellipsoidal plasmonic nanoparticles suspended in viscous liquid. Within the kinetic approach we find the temperature dependence of the components of LMC permittivity tensor. We show that thermal transitions between dispersion states with different topologies of isofrequency surfaceare possible. We also study the impact of thermal fluctuations on optical nonlinearity of LMC.

Nonlinear version of Einstein coefficients in parametric conversions

Shin Arahira, Hitoshi Murai, and Hironori Sasaki

Doc ID: 280833 Received 14 Nov 2016; Accepted 12 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: In this paper we report experimental investigation on relation between efficiencies of stimulated and spontaneous parametric conversion processes in nonlinear optical devices. We have found that the generation rate of photon-pairs in the spontaneous process, μ, and the conversion efficiency in the stimulated process, η, had a simple linear relationship of μ=Kη. The factor of proportionality, K, was found to be 1 pair/Hz/s, regardless of the types of the devices and the parametric processes. This new finding implies that there is a simple relationship, like the Einstein coefficients, between the spontaneous and the stimulated processes of optical nonlinearities.

Spatial localization of electromagnetic modes in noise-like random one-dimensional dielectric heterostructures

Miguel Eduardo Mora-Ramos, José Escorcia-García, and David Becerra-García

Doc ID: 279003 Received 18 Oct 2016; Accepted 10 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: This work theoretically investigates the propagation of electromagnetic signals in a new-type of layered systems denominated noise-like random heterostructures. These heterostructures, designed on the basis of two different porous silicon layers, showed a wide photonic bandgap and can be modulated with the noise amplitude. These systems are also suitable for strong spatial localization of electromagnetic modes, depending on the noise amplitude and seed of generation, reaching high values up to 104. In addition, the localization length decreased with the noise amplitude and showed at minimum inside the bandgap. This kind of heterostructures can be used in photonics applications such as omnidirectional mirrors as well as in lasing devices.

Analysis of the modification of four-wave mixing phasematching by stimulated Brillouin scattering

el-abed haidar, Benjamin Eggleton, and C. Martijn de Sterke

Doc ID: 281080 Received 29 Nov 2016; Accepted 10 Jan 2017; Posted 10 Jan 2017  View: PDF

Abstract: Controlling the phase matching condition of four-wave mixing (FWM) using stimulated Brillouin scattering (SBS) was experimentally demonstrated but the full extent of the capabilities of this method have remained unknown. Here we theoretically and numerically investigate these capabilities, considering theSBS and the FWM separately. We show that, with modest optical power, exponential gain is achievable for normal dispersion. The method is limited by SBS-induced power variations and by the need to limit the SBS power levels.

Error analysis for noise reduction in 3D deformation measurement with digital color holography

Pascal Picart, Silvio Montresor, Leonid Muravsky, and Oleksandr Sakharuk

Doc ID: 281780 Received 29 Nov 2016; Accepted 10 Jan 2017; Posted 17 Jan 2017  View: PDF

Abstract: This paper presents an analysis of phase errors generated by advanced noise removal algorithms applied to phase measurements obtained from digital holographic interferometry. The output phase error is analyzed considering two contributions that are the error generated by the de-noising method and the error due to the phase noise. In addition, a third type of error allows quantifying the ability of any algorithm to estimate the initial noise level. A comparison of several de-noising algorithms is presented to independently assess the three types of errors from a dataset of simulated fringe patterns with controlled realistic noise. The results exhibit the best method for which the output error, together with the method error, is the smaller one. Knowing the error method is advantageously applied to digital color holography experiments in which deformation measurements of an object submitted to mechanical strength are given with a percentage of error due to the de-noising algorithm.

Fabry-Perot cavity locking with phase-locked frequency-synthesized light

Sheng Feng and peng yang

Doc ID: 279263 Received 21 Oct 2016; Accepted 07 Jan 2017; Posted 09 Jan 2017  View: PDF

Abstract: We propose to use frequency-synthesized light for Fabry-Perot cavity locking. The scheme allows arbitrary control of the amplitudes and the phases of the modulation sidebands relative to the carrier. In comparison with phase-modulated light, use of frequency-synthesized light provides an artful way to suppress laser instability arising from intracavity relative intensity fluctuation and residual amplitude modulation (RAM) of light and, thereby, may considerably facilitate laser frequency stabilization at an unprecedented level. We experimentally demonstrate the scheme with RAM fluctuation between 0.3 mHz - 100 mHz reduced by 2 orders of magnitude and being 10 dB below the RAM noise of a phase-modulated light, when a simple RAM servo is activated.

An adaptive mode solver for varying refractive-index profile's waveguides with modified spectral element method

Jianxin Zhu and HAO YANG

Doc ID: 278833 Received 14 Oct 2016; Accepted 07 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: A mode solver based on the spectral element method with mesh adaptation is proposed to calculate the modal characteristics of a semivectorial field in open varying-index optical waveguides. General optical waveguides with varying refractive-indices are studied for the transverse electric (TE) and transverse magnetic (TM) cases, where perfectly matched layers (PMLs) are used to truncate the unbounded waveguides. The optical field expanded by a suitable set of orthogonal basis points (Gauss-Lobatto-Legendre (GLL) or Gauss-Chebyshev-Collocation (GCC) points) through spectral element method are all represented by processing of characterization of composite material through mesh adaptation. By this combined solver, a large number of accurate PML modes can be easily calculated. And our results are still found to be in good agreement with those produced by other various numerical methods, however, more efficiency. By the way, the relations of the PML modes distribution to the parameters of PMLs are analysed through the pitchfork phenomenon in the spectrum.

Limits of Femtosecond Fiber Amplification by Parabolic Pre-Shaping

Walter Fu, Yuxing Tang, Timothy McComb, Tyson Lowder, and Frank Wise

Doc ID: 277970 Received 03 Oct 2016; Accepted 05 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: We explore parabolic pre-shaping as a means of generating and amplifying ultrashort pulses. We develop a theoretical framework for modeling the technique and use its conclusions to design a femtosecond fiber amplifier. Starting from 9 ps solitons, we obtain 4.3 μJ, nearly transform-limited pulses 275 fs in duration, simultaneously achieving over 40 dB gain and 33-fold compression. Finally, we show that this amplification scheme is limited by Raman scattering, and outline a method by which the pulse duration and energy may be further improved and tailored for a given application.

Engineering of closely packed SOI waveguide arraysfor Mode Division Multiplexing applications

Philippe Velha, Isabella Cerutti, and Nicola Andriolli

Doc ID: 278826 Received 14 Oct 2016; Accepted 04 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: On-chip optical communications require high-performance, energy-efficient, and scalable multiplexingtechniques for enabling high parallelism. Mode division multiplexing (MDM) is gaining momentum,but its scalability is limited by the crosstalk and the (de)multiplexing complexity.To overcome such limitations, this paper proposes the exploitation of super-modes in closely-spaced arrays of waveguides. A theoretical approach demonstrates the generation of super-modes achieved byperturbing the uniformity of waveguide arrays. Spectral characterization shows a crosstalk of about -20dB on the C band, in a non-uniform array of five silicon-on-isolator waveguides.

Analysis of the Polarization of a single-mode VCSEL Subject to Parallel Optical Injection

Angel Valle, Ana Quirce, Alexandra Popp, Florian Denis-le Coarer, Pablo Pérez, Luis Pesquera, Yanhua Hong, Hugo Thienpont, Krassimir Panajotov, and Marc Sciamanna

Doc ID: 281057 Received 17 Nov 2016; Accepted 03 Jan 2017; Posted 03 Jan 2017  View: PDF

Abstract: We investigate experimentally and theoretically the polarization switching found in a single-transverse mode VCSEL when subject to parallel optical injection. Our analysis focuses on a recently observed state in which injection locking of the parallel polarization and excitation of the free-running orthogonal polarization of the VCSEL are obtained. A simple nonlinear dependence between the power of both linear polarizations and the frequency detuning is found. Also the total power emitted by the VCSEL is constant and independent on the injected optical power and on the frequency detuning. We check these results experimentally for a variety of frequency detunings and bias currents applied to the device. We report experimental and theoretical stability maps in the injected power-frequency detuning plane for different bias currents identifying the regions in which the state is observed. A simple analytical expression that describes the map boundary for large and negative frequency detunings is obtained. This provides a simple method to extract the linear dichroism of the device.

1030 nm Yb3+ DFB short cavity silica-based fiber laser

Oleg Butov, Alexey Bazakutsa, Konstantin Golant, Mikhail Vyatkin, Sergei Popov, Yuri Chamorovsky, and Andrey Rybaltovsky

Doc ID: 277947 Received 30 Sep 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: Narrow line distributed feedback (DFB) fiber laser based on a 16mm-long Bragg grating inscribed in a purpose-made strongly activated and highly photosensitive silica fiber was fabricated and tested. A fiber preform synthesized by means of the surface-plasma vapor deposition (SPCVD) and a standard Bragg grating writing technology with the use of an ArF excimer laser and a π-shifted phase mask were applied to fiber drawing and grating writing respectively. A single-mode generation regime of the DFB laser core-pumped at a wavelength of 976 nm was obtained, measured line width being less than 8 kHz.

High power fiber laser based on tandem pumping

Pu Zhou, Hu Xiao, Jinyong Leng, Xu Jiangming, Zilun Chen, hanwei zhang, and Zejin Liu

Doc ID: 278037 Received 03 Oct 2016; Accepted 03 Jan 2017; Posted 05 Jan 2017  View: PDF

Abstract: Power scaling of fiber laser is challenged by the brightness of pump source, nonlinear effect, modal instability and so on. Pumping active fiber by using high-brightness fiber laser instead of laser diode might be a solution for the brightness limitation and modal instability. In this paper, we will present a general review on the advancement of various kinds of high power fiber laser based on tandem pumping scheme in the past few years for the first time. The requirements for tandem pumping Ytterbium (Yb), Erbium (Er), Thulium (Tm) and Holmium (Ho) doped fiber are analyzed and corresponding achievement are summarized, hundreds watt of ~1020 nm, ~1500 nm, and 1900 nm fiber laser, hundred-watt level ~1150 nm and ~1180 nm fiber laser have been successfully achieved. Those powerful fiber lasers with high brightness are employed as pump source for Yb, Er, Tm and Ho doped fiber. We will present the recent experimental result of a 3.5 kilowatt Yb-doped fiber amplifier in all-fiber format in addition to previous typical achievements. The underlying challenging for further power scaling, including the nonlinear effect suppression and special fiber design requirement, is briefly discussed. Exploring tandem pumping to novel application fields is provided.

Pulse dynamics in all-normal dispersion ultrafast fiber lasers

Xuewen Shu and Du Yueqing

Doc ID: 278177 Received 05 Oct 2016; Accepted 30 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We present a numerical investigation of pulse shape evolution and pulse regime transformation in an all-normal dispersion mode-locked fiber laser. We find that the pump strength and spectral filtering have great effects on the properties of the generated dissipative solitons. The pulse has a parabolic intensity profile and linear chirp when the pump strength is large enough under certain bandwidth of the spectral filter. Such a parabolic pulse works in the intermediate regime between the dissipative soliton and similariton, however, the pulse looks more like a dissipative soliton. Pulse regime transformation will happen when the pump strength is large enough, the pulse will become multi-pulse, bound-state pulse or noise-like pulse under different filter bandwidth and pump strength. The results of our numerical simulations could offer a better understanding of the dynamics of all-normal dispersion mode-locked fiber lasers and also provide an insight into the dissipative fiber laser systems.

Resolution matching in laser direct printing of computer-generated hologram

Xingpeng Yan, Jian Su, Xiaoyu Jiang, Yingqing Huang, and Yibei Chen

Doc ID: 278912 Received 21 Oct 2016; Accepted 29 Dec 2016; Posted 13 Jan 2017  View: PDF

Abstract: A configuration for laser direct printing(LDP) of computer-generated hologram(CGH) is proposed and implemented. The CGH is generated by ray-tracing method, displayed by a digital micromirror device(DMD), demagnified by a bi-telecentric lens, and recorded on a holographic plate. In order to prevent aliasing and distortion, the resolution matching between the generation and printing of CGH is established and analyzed, and the parameters of the system are optimized. The theoretical results demonstrate that the proposed LDP system of CGH and the parameter-optimizing criterion for the LDP can record and reconstruct the hologram well.

Ultra-Broadband LWIR Metamaterial Absorber based on a Double-Layer Metasurface Structure

Kadir Ustün and GONUL TURHAN-SAYAN

Doc ID: 277920 Received 30 Sep 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: In this paper, we report a metamaterial absorber design that achieves a broad absorption band encompassing the whole long wavelength infrared region (LWIR). The structure consists of two parallel metasurfaces buried into the amorphous silicon dielectric layer where the minimum size for all possible planar details does not go below 1 µm making the use of standard optical lithography possible for fabrication. Namely, the suggested metamaterial absorber is an easy to fabricate structure as well. The dielectric layer of the structure is placed over a metallic ground plane layer that inhibits the transmission of incident waves. A substrate underneath the ground plane may also be needed only for mechanical support. This structure achieves the absorptivity of about 90% in the full LWIR band in case of normal incidence being independent of polarization. The polarization insensitivity is achieved by the four-fold symmetry of the structural geometry. The absorber also shows reduced sensitivity to off-normal incidence angles, achieving approximately 80% of absorptivity up to the incidence angle of 45 degrees. Such a metamaterial absorber design would find applications in thermal emitters/coolers and in thermal infrared sensors.

Development of weak coherent 0π optical pulses in a ring resonator with a dynamic recurrent loop

Makoto Tomita and Yukari Suzuki

Doc ID: 278032 Received 24 Oct 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: We investigated the development of weak coherent 0π optical pulses in a ring resonator with a dynamic recurrent loop. Using this recurrent system, we measured transmitted pulse profiles as a function of the recurrence time, i.e., the number of times pulses passed through the resonator. As the number increased, the transmitted pulse profiles developed oscillating structures characteristic of weak coherent 0π optical pulses. The pulse area decayed exponentially to 0π, independent of the pulse duration and pulse shape, thus obeying the pulse area theorem described by McCall and Hahn in the linear regime. Successful observation of the coherent 0π pulses demonstrated the potential application of the system to a wide variety of experiments in which pulse states are examined after passing through resonators of exactly the same resonance frequency, with an ultra-high Q value, an arbitrary number of times.

Interaction of doughnut-shaped laser pulses with glasses

Vladimir Zhukov, Alexander Rubenchik, Mikhail Fedoruk, and Nadezhda Bulgakova

Doc ID: 279191 Received 21 Oct 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Non-Gaussian laser beams can open new opportunities for microfabrication, including ultrashort laser direct writing. Using a model based on Maxwell’s equations, we have investigated the dynamics of doughnut-shaped laser beams focused inside fused silica glass, in comparison with Gaussian pulses of the same energy. The laser propagation dynamics reveals intriguing features of beam splitting and sudden collapse toward the beam axis, overcoming the intensity clamping effect. The resulting structure of light absorption represents a very hot, hollow nanocylinder which can lead to an implosion process that brings matter to extreme thermodynamic states. Monitoring the simulations of the laser beam scattering has shown considerable difference in both the blue shift and the angular distribution of scattered light for different laser energies, suggesting that investigations of the spectra of scattered radiation can be used as a diagnostic of laser-produced electron plasmas in transparent materials.

Dispersion Control in Coated Wire Media Slabs

John Brownless, C. Martijn de Sterke, Björn C. P. Sturmberg, Alexander Argyros, and Boris Kuhlmey

Doc ID: 280420 Received 09 Nov 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Wire media (WM) metamaterials have many applications, specifically imaging, due to their hyperbolic dispersion properties. Here we consider WM comprised of wires with dielectric coatings, and explore how the coating affects the dispersion and its possible applications. Using an effective medium approximation we find the slab modes of dielectric coated WM and compare results to numerical simulations. This shows that for potential applications we must consider parameters where these approximations cannot be used. We use numerical results to further explore the effect of strong coatings and lattice distortion, and develop a semi-analytic approach to tailor the dispersion relation of WM slabs. We use this to find a coating that optimizes control over the dispersion in one dimension, and discuss advantages for imaging applications such as the metamaterial hyperlens and the resonant metalens.

Laser cooling of solids under influence of surface phonon polaritons

Galina Nemova and Raman Kashyap

Doc ID: 280575 Received 10 Nov 2016; Accepted 27 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Laser cooling of solids with anti-Stokes fluorescence in rare-earth doped low-phonon samples, which support surface phonon polaritons (SPhPs), placed in the vicinity of the sample supporting SPhP in the same or different wavelength region is considered in this paper. As an example, the laser cooling process in an ytterbium-doped yttrium aluminium garnet (Yb3+:YAG) sample placed near YAG as well as silicon carbide (SiC) samples has been investigated. All Yb3+:YAG, YAG, and SiC samples can support SPhPs but in different frequency ranges. It is shown that for short distances between samples, when SPhPs propagating in the sample undergoing laser cooling and SPhPs propagating in the next sample supported at room temperature, are coupled the laser cooling process can deteriorate substantially. In opposite case the SPhPs do not influence the cooling process significantly even if the distance between the samples is less than the dominant wavelength of thermal radiation. The influence of coupled SPhPs on the laser cooling process in the case of samples with different sizes and for the different distances between samples is investigated. These results are important for development of optical solid state cryocoolers.

Finite Pulse Effects in the Single and Double Quantum Spectroscopies

Václav Perlík, Juergen Hauer, and Frantisek Sanda

Doc ID: 273545 Received 10 Aug 2016; Accepted 23 Dec 2016; Posted 23 Dec 2016  View: PDF

Abstract: When modelling experimental 2D spectra, the effects of finite pulse durations are usually neglected to optimize computational costs. We present an analytic treatment of finite pulse duration effects on electronic 2D spectra. While photon echo signal is more robust, the double quantum signal shows unexpected dependencies, based on mixing of absorptive and dispersive components. In the limit of Lorentzian pulse shapes, we compare the exact results of our analytically solvable approach to standard approximations made for finite pulse effects. We show how these approximations fail to reproduce the correct the phase and amplitudes of vibrational oscillations.

Study of slow-light-enhanced membrane photodetector for realizing on-chip interconnection with low power consumption

Zhichen Gu, Takuo Hiratani, Tomo Amemiya, Shigehisa Arai, and nobuhiko nishiyama

Doc ID: 278692 Received 13 Oct 2016; Accepted 21 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Slow-light propagation can be used to enhance light-matter interactions such as material loss and gain, enabling, for example, to realize an ultracompact photodetector (PD) with extremely short absorption length. This type of ultrasmall-capacitance PD can be expected to simultaneously provide large bandwidth and sufficient voltage output without using electrical amplifiers such as trans-impedance amplifiers in conventional receiver circuits, thus realizing ultralow-power-consumption optical-to-electrical conversion, which is one of the key issues faced in an on-chip optical interconnection. We designed a slow-light-enhanced waveguide-type GaInAs p-i-n-PD by using the 3D finite-difference time domain method. As a result, it was found that a cut-off frequency of 19.6 GHz with moderate output voltage, which was attributed to the high impedance characteristic, can be obtained with a 5.5-µm-long PD.

Three-dimensional vector wave bound states in the continuum

Xiangdong Zhang, Jinhua Li, and Jun Ren

Doc ID: 280711 Received 11 Nov 2016; Accepted 21 Dec 2016; Posted 03 Jan 2017  View: PDF

Abstract: Recently, bound states for a certain polarized electromagnetic wave have been demonstrated to exist within the radiation continuum in large periodic arrays and open resonators, in analogy with embedded eigenvalues in certain quantum systems. Here we demonstrate that it may be possible to induce three-dimensional photonic embedded eigenvalues for vector waves with both polarizations in a subwavelength open scattering system. These bound states have infinitely large lifetimes, which are very sensitive to the absorption and fluctuation of the structure. Although the effect of absorption on the bound states in the continuum (BICs) is strong, they can always be overcome by introducing optical gains in the systems. However, to obtain the BICs, precise control of the aspect ratio of the structure is needed.

Generation of High Power Short Terahertz Pulses using Chirped Aperiodically Poled Structures

Alireza Yahaghi, Koustuban Ravi, Arya Fallahi, and Franz Kaertner

Doc ID: 279975 Received 03 Nov 2016; Accepted 07 Dec 2016; Posted 07 Dec 2016  View: PDF

Abstract: We introduce a collinear scheme for the highly efficient generation of broadband, single or few-cycle high power terahertz (THz) pulses using optical rectification. For this purpose, two concepts are introduced and thoroughly analyzed. The first concept is the generation of chirped broadband terahertz pulses using chirped aperiodically poled electro optic crystals. The second concept involves the compression of the terahertz pulses extracted from the aperiodically poled structure using a chirped mirror. An illustrative design employing cryogenically cooled aperiodically poled lithium niobate (APPLN) crystals and appropriate chirped mirrors ispresented. It is shown that the the presented design allows the optical pulse to be re-used in subsequent generation stages, resulting in optical-to-THz conversion efficiencies in excess of 5% for terahertz radiation centered around 0.3 THz. Analytic solutions and numerical calculations are presented. In order to design a crystal with optimum conversion efficiency, we take advantage of binary optimization techniques. This work paves the way for the generation of broadband terahertz radiation with several mJ of pulse energy using large area aperiodically poled structures.

Analytical solutions to the finite-pulse Bloch model for multidimensional coherent spectroscopy

Christopher Smallwood, Travis Autry, and Steven Cundiff

Doc ID: 273905 Received 18 Aug 2016; Accepted 08 Nov 2016; Posted 09 Nov 2016  View: PDF

Abstract: We present perturbative analytical solutions to the optical Bloch equations at third-order, with finite duration Gaussian pulse envelopes. We find that a given double-sided Feynman diagram in this approximation can be conveniently described in the frequency domain as a product of the expression in the impulsive limit and a finite-pulse factor. Finite-pulse effects are Feynman-diagram-dependent, however, and include nontrivial phase corrections that can occur even in the case of transform-limited pulses. The results constitute a practical framework for modeling phenomena in multidimensional coherent spectroscopy that cannot easily be captured in the impulsive limit, including the roles of bandwidth, resonance, and pulse chirp.

Modulation instability induced by higher-order nonlinear dispersions in nonlinear positive-negative index couplers with exponential saturable nonlinearity

Mohamadou Alidou, Aboukar NO LAST NAME GIVEN, and Alim Dia

Doc ID: 264583 Received 04 May 2016; Accepted 04 Oct 2016; Posted 04 Oct 2016  View: PDF

Abstract: We study the modulational instability (MI) in positive-negative couplers with higher-order effects and exponential saturable nonlinearity. Special attention is paid tothe influence of self-steepening (SS); intrapulse Raman scattering and second-order nonlinear dispersion (SOND) on the MI gain. The results show that saturable nonlinearity can be used to control the generation of sidebands through the coupler. We show that in normal dispersion regime, the instability gain exists even if theperturbation frequency ($\Omega$) is zero. The instability gain at $\Omega=0$ is nil, when the dispersion is anomalous. We find that the magnitude and sign of SOND exert strong influences on MI sideband. Moreover, by adjusting the various parameters such as SS, intrapulse Raman scattering, and SOND we obtain new instability regions.These results can be helpful to understand the generation of soliton-like exitaction in nonlinear oppositely coupler and can be potentially useful for future experiments.

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