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Journal of the Optical Society of America B

Journal of the Optical Society of America B

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Early Posting

Accepted papers to appear in an upcoming issue

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Articles 1 to 20 of 27 Next Page >>

November


Modulated photonic band gaps generated by high-order wave mixing

  • Mengqin Gao, Zhiguo Wang, Zakir Ullah, Haixia Chen, Dan Zhang, Yiqi Zhang, and Yanpeng Zhang
  • received 09/23/2014; accepted 11/20/2014; posted 11/20/2014; Doc. ID 223519
  • [full text: PDF (1319) KB)]
  • Abstract: For the first time, we investigate the photonic band gap (PBG) structure through scanning the frequency detunings of the probe field, dressing field and coupling field in the static and moving electromagnetically induced grating (EIG) field. When we scan the frequency detuning of the coupling field, the PBG structure and six wave mixing band gap signal (SWM BGS) appear at the right of the electromagnetically induced transparency (EIT) position. But the PBG structure and SWM BGS appear at the left of the EIT position in case of scanning the probe field frequency detuning. Also, on the condition of scanning the probe field frequency detuning, the SWM BGS appears in two frequency ranges. Moreover, in the moving PBG structure, the nonreciprocity of SWM BGS can be obtained. Furthermore, the intensity, width, location of the SWM BGS can be modulated through changing the frequency detunings and intensities of the probe field, dressing field and coupling field, sample length and the frequency difference of coupling fields in EIG. Such scheme could have potential applications in optical diodes, amplifiers and quantum information processing.

Keywords (OCIS):

  • (190.0190) Nonlinear optics : Nonlinear optics
  • (190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
  • (300.2570) Spectroscopy : Four-wave mixing
  • (190.4223) Nonlinear optics : Nonlinear wave mixing

Propagation of Airy Gaussian vortex beams through slabs of right-handed materials and left-handed materials

  • Bo Chen, Chidao Chen, Xi Peng, and Dongmei Deng
  • received 09/12/2014; accepted 11/19/2014; posted 11/20/2014; Doc. ID 223054
  • [full text: PDF (4535) KB)]
  • Abstract: By using the method of ABCD matrix, the propagation of Airy Gaussian vortex (AiGV) beams through slabs of right-handed materials (RHMs) and left-handed materials (LHMs) is reported. Based on the Huygens diffraction integral, an approximate analytical propagation equation of AiGV beams is derived. Using numerical simulations, we study the intensity and phase distributions of the AiGV beams in RHMs and LHMs. We find that the optical vortex can destroy the center lobe of the AiGV beams, and the center lobe can reconstruct due to the acceleration of the vortex and the AiGV beam is not consistent. We also investigate the influence of different χ0 on the propagation of the AiGV beams through slabs of RHMs and LHMs, which can control the AiGV beams that tends to an Airy vortex beam with the smaller value, and a Gaussian vortex beam with the larger one. In addition, we elucidate the energy flow and the angular momentum of the AiGV beams.

Keywords (OCIS):

  • (010.3310) Atmospheric and oceanic optics : Laser beam transmission
  • (070.2590) Fourier optics and signal processing : ABCD transforms
  • (350.3618) Other areas of optics : Left-handed materials

A refined model for Talbot-Lau matter-wave optics with pulsed photo-depletion gratings

  • Nadine Dörre, Philipp Haslinger, Jonas Rodewald, Philipp Geyer, and Markus Arndt
  • received 09/24/2014; accepted 11/18/2014; posted 11/19/2014; Doc. ID 223456
  • [full text: PDF (3810) KB)]
  • Abstract: We analyze time-domain Talbot-Lau interferometry of organic cluster beams that are exposed to pulsed photo-depletion gratings in the vacuum ultraviolet (VUV). We focus in particular on the analysis of the complex (phase and absorption) character of the optical elements. The discussion includes the role of wave front distortions due to mirror imperfections on the nanometer level and the effect of finite coherence in the diffraction gratings. This improved understanding of the interferometer allows us to extract new information on optical properties of anthracene and ferrocene clusters and to define conditions for future matter-wave experiments.

Keywords (OCIS):

  • (020.0020) Atomic and molecular physics : Atomic and molecular physics
  • (260.3160) Physical optics : Interference
  • (260.7210) Physical optics : Ultraviolet, vacuum
  • (270.0270) Quantum optics : Quantum optics
  • (020.1335) Atomic and molecular physics : Atom optics

Femtosecond laser filamentation with microlens array in air

  • Tingting Xi, Zuoqiang Hao, and Zhijie Zhao
  • received 07/23/2014; accepted 11/17/2014; posted 11/19/2014; Doc. ID 217599
  • [full text: PDF (804) KB)]
  • Abstract: By performing numerical studies, we have shown that during the propagation of femtosecond laser pulses with microlens array in air, the filamentation with an earlier onset can be prolonged almost twice as long as that generated in the case of single lens. The elongation of the filamentation results from the interaction of the regular filaments whose positions correspond to those of the lenslets. The enhancement of supercontinuum is also observed with different ratio as a function of wavelength. More efficient enhancement in the blue side of the spectrum can be obtained by increasing the size of lenslet but at the cost of shortening the filamentation. This process is strongly influenced by the spatiotemporal dynamics of the laser pulse. The microlens array offers a new way to control the filamentation and supercontinuum emission for the long-distance applications of the femtosecond laser pulse.

Keywords (OCIS):

  • (260.5950) Physical optics : Self-focusing
  • (320.2250) Ultrafast optics : Femtosecond phenomena

Exact Dispersion Equation of TE Leaky Modes for Nonhomogeneous Optical Waveguides

  • Jianxin Zhu and Jia Zheng
  • received 07/29/2014; accepted 11/14/2014; posted 11/18/2014; Doc. ID 219975
  • [full text: PDF (373) KB)]
  • Abstract: For the modal expansion in the nonhomogeneous optical waveguides, it is necessary to develop a high precision mode solver. In this paper, the differential transfer matrix method is applied, and an exact dispersion equation is built generally by the matrix similarity transformation and may be solved iteratively by Newton’s method. In justification of our proposed method, the truncation error analysis for the old method is provided. Further, the asymptotic solutions in the form of simpler formulae for the approximated equation are derived. These approximate analytic results are valuable and may well act as initial guesses for numerical methods. More accurate results can be gotten by our method in numerical simulations.

Keywords (OCIS):

  • (060.2270) Fiber optics and optical communications : Fiber characterization
  • (230.7400) Optical devices : Waveguides, slab

Investigating the impact of correlated white noises on the bistability behaviour in an optical three-level bistable system

  • Tayebeh Naseri and Rasoul Sadighi-Bonabi
  • received 07/01/2014; accepted 11/14/2014; posted 11/14/2014; Doc. ID 214513
  • [full text: PDF (474) KB)]
  • Abstract: The effect of correlated white noises on the optical bistability behavior of three-level atomic system is investigated theoretically. Noise-induced bistability caused by fluctuating atomic coherence is demonstrated in an atomic optical bistable system consisting of three-level atoms in -type configurations confined in an optical ring cavity. The output field as a result of enhanced Kerr nonlinearity induced by atomic coherence in the electromagnetically induced transparency system is fluctuating due to the noise in laser parameters and cooperativity parameter and is mainly responsible for such induced bistability in the system. It is found that with the cross-correlation noises, the hysteresis loop of optical bistability can be clearly expanded in comparison with the deterministic case and the atomic system could show multistability behavior. This is specifically considerable for positive cross-correlation noises where it could expand the domain of hysteresis loop. In the presented atomic system the numerical result shows that noise can induce bistability in the absence of spontaneous generated coherence (SGC). Furthermore, it was more interesting when it is noticed that the noise could induce bistability when the system is below its deterministic threshold for bistability.

Keywords (OCIS):

  • (190.0190) Nonlinear optics : Nonlinear optics
  • (190.1450) Nonlinear optics : Bistability
  • (190.4360) Nonlinear optics : Nonlinear optics, devices
  • (270.1670) Quantum optics : Coherent optical effects

Increased bandwidth with flattened and low dispersion in a horizontal double-slot silicon waveguide

  • Changjing Bao, Yan Yan, Lin Zhang, Yang Yue, Nisar Ahmed, Anuradha Agarwal, Lionel Kimerling, Jurgen Michel, and Alan Willner
  • received 09/12/2014; accepted 11/14/2014; posted 11/14/2014; Doc. ID 223037
  • [full text: PDF (833) KB)]
  • Abstract: We propose a horizontal double-slot silicon waveguide to achieve flattened and low dispersion from -26 ps/(km•nm) to 21 ps/(km•nm) over an 878 nm wavelength range, which is much larger than that obtained from a single-slot waveguide. The mechanism of using this double-slot structure to increase the bandwidth is studied. Our study shows that the mode transition process from one strip mode to two slot modes helps extend the bandwidth of the flattened and low dispersion to longer wavelengths compared to a single-slot waveguide. Furthermore, we show by simulation the supercontinuum generation with a 3-dB bandwidth of 188 nm in all-normal-dispersion profile with an input pulse of 50 fs.

Keywords (OCIS):

  • (130.3120) Integrated optics : Integrated optics devices
  • (260.2030) Physical optics : Dispersion
  • (250.4390) Optoelectronics : Nonlinear optics, integrated optics

Casimir force between metal and graphene sheets

  • J. Martinez and M. Jalil
  • received 09/10/2014; accepted 11/13/2014; posted 11/20/2014; Doc. ID 222836
  • [full text: PDF (1050) KB)]
  • Abstract: The Casimir force between neutral plates is attractive. For the Casimir force to be really useful one must be able to switch between attraction and repulsion. Exploiting the experimentalist's ability to change the sign of the charge carriers in graphene, we show how the sign of the Fresnel reflection coefficients can be reversed. This gives rise to a Casimir force between a metal sheet and graphene which can be either attracrive or repulsive; we illustrate it for a dielectric cylinder and a graphene sheet.

Keywords (OCIS):

  • (270.5580) Quantum optics : Quantum electrodynamics
  • (160.4236) Materials : Nanomaterials

Mini-Review: Examining Nanophotonics for Integrated Hybrid Systems: A Review of Plasmonics Interconnects and Modulators Using Traditional and Novel Materials

  • Alexandra Boltasseva, Marcello Ferrera, Vladimir Shalaev, and Nathaniel Kinsey
  • received 11/04/2014; accepted 11/12/2014; posted 11/21/2014; Doc. ID 226079
  • [full text: PDF (674) KB)]
  • Abstract: The scaling which has governed the continual increase in density, performance, and efficiency of electronic devices is rapidly reaching its inevitable limitations. In order to sustain the trend of ever increasing bandwidth and performance, new technologies are being considered. Among the many competitors, nanophotonic technologies are especially poised to impact the field of integrated devices. Here, we examine the available technologies, both traditional photonics and plasmonics, with an emphasis on the latter. A summary of the previous advances in the field of nanophotonics (interconnects and modulators), along with more recent works investigating novel and CMOS-compatible materials, are presented with a graphical comparison of their performance. We suggest that nanophotonic technologies offer key advantages for future hybrid electro-photonic devices, where the movement towards new material platforms is a precursor to high-performance, industry-ready devices.

Keywords (OCIS):

  • (130.0130) Integrated optics : Integrated optics
  • (160.3130) Materials : Integrated optics materials
  • (230.4110) Optical devices : Modulators
  • (230.7370) Optical devices : Waveguides
  • (250.5403) Optoelectronics : Plasmonics

Scaling of the nonlinear response of the surface plasmon polariton at a metal/dielectric interface

  • Alexandre Baron, Stéphane Larouche, Daniel Gauthier, and David Smith
  • received 10/06/2014; accepted 11/12/2014; posted 11/14/2014; Doc. ID 223982
  • [full text: PDF (677) KB)]
  • Abstract: Plasmonic systems involve interfaces containing both a metal and a dielectric material. In an effort to investigate the scaling of the nonlinear response of the surface plasmon polariton at a metal/dielectric interface, where both the metal and the dielectric present optical nonlinearity, we introduce a figure-of-merit that quantifies the contribution of the metal and the dielectric to the nonlinear response in this specific situation. In the case of self-action of the surface plasmon polariton for the gold/dielectric interface, we predict that the dielectric nonlinear response is dominant for strongly nonlinear dielectrics such as polydiacetylenes, chalcogenide glasses or even semiconductors. The gold nonlinear response is dominant only in cases involving weakly nonlinear dielectrics such as silicon dioxide or aluminium oxide. We verify the relevance of the metric by investigating the process of optical switching via the third-order nonlinear response and discuss which gold/dielectric combinations have better switching behaviors.

Keywords (OCIS):

  • (190.4350) Nonlinear optics : Nonlinear optics at surfaces
  • (190.5940) Nonlinear optics : Self-action effects
  • (240.6680) Optics at surfaces : Surface plasmons

A low loss dual-band double negative chirped metamaterial

  • Tun Cao, Chenwei Wei, and Martin Cryan
  • received 09/24/2014; accepted 11/12/2014; posted 11/14/2014; Doc. ID 220252
  • [full text: PDF (2362) KB)]
  • Abstract: We present numerical modelling of a dual-band double negative chirped metamaterial(MM) in the optical region. The MM has an elliptical nanohole array (ENA) penetrating through a metal/dielectric material/metal (Au- Al2O3-Au) film. We consider the case when the chirp is introduced by displacing the positions of the ENA along the short axis of the elliptical apertures inside the primitive cell. We demonstrate that these chirped MMs can provide a dual-band negative refractive index (NRI) with simultaneous negative permittivity and permeability in both near infrared (N-IR) region and mid infrared (M-IR) region respectively. As the neighbouring elliptical holes are moved closer to each other the NRI in the N-IR region blue shifts to the shorter wavelength with a decreasing magnetic resonance, whereas the NRI in the M-IR region red shifts to the longer wavelength with an increasing magnetic resonance. This structure possesses a high value of Figure-of-Merit owing to the large size of the elliptical apertures.

Keywords (OCIS):

  • (240.6680) Optics at surfaces : Surface plasmons
  • (350.3618) Other areas of optics : Left-handed materials
  • (160.3918) Materials : Metamaterials

Second order sensitivity analysis for a photonic crystal waveguide bend

  • Zhen Hu and Ya Yan Lu
  • received 08/28/2014; accepted 11/11/2014; posted 11/14/2014; Doc. ID 221920
  • [full text: PDF (367) KB)]
  • Abstract: Sensitivity analysis provides important information on the tolerance to fabrication imperfections for any designed devices. Standard sensitivity analysis relies on the first order partial derivatives of a response function of the device with respect to the design parameters. These derivatives are also useful in the device optimization process when a gradient based optimization method is used. The first order sensitivity analysis becomes inadequate if the first order derivatives are small or zero. In this paper, an efficient method for computing the second order partial derivatives is developed for idealized two-dimensional photonic crystal devices with circular cylinders, where the response function is the normalized power transmission coefficient in an output waveguide and the design parameters are the radii of the cylinders. Based on that, a second order sensitivity analysis is performed for a $90^\circ$ photonic crystal waveguide at the frequency where the transmission coefficient is close to 1.

Keywords (OCIS):

  • (000.3860) General : Mathematical methods in physics
  • (130.5296) Integrated optics : Photonic crystal waveguides
  • (230.5298) Optical devices : Photonic crystals

Phase-controlled optical Faraday rotation in a closed-loop atomic system

  • Mariye Veisi, Azar Vafafard, and Mohammad Mahmoudi
  • received 09/02/2014; accepted 11/11/2014; posted 11/14/2014; Doc. ID 222371
  • [full text: PDF (537) KB)]
  • Abstract: We investigate the nonlinear optical Faraday rotation (OFR) of a probe field passing through a double V–type closed-loop atomic system in the absence of external static magnetic field. Enhancement OFR is obtained by applying the control fields to establish the closed-loop configuration. It is shown that the scattering of both control fields into the probe field mode via wave mixing induce an OFR enhancement. We find that the rotation of polarization plane in the nonlinear OFR depends on the intensity and relative phase of applied fields and can be controlled by these parameters. It is demonstrated that applying a microwave field to the system has a constructive role in enhancement of phase-controlled nonlinear OFR.

Keywords (OCIS):

  • (230.2240) Optical devices : Faraday effect
  • (270.1670) Quantum optics : Coherent optical effects
  • (270.4180) Quantum optics : Multiphoton processes
  • (190.4223) Nonlinear optics : Nonlinear wave mixing

Controlling ablation mechanisms in sapphire by tuning the temporal shape of fs-laser pulses

  • J. Hernandez-Rueda, J. Siegel, M. Galvan-Sosa, A. Ruiz de la Cruz, M. Garcia Lechuga, and J. Solis
  • received 08/12/2014; accepted 11/10/2014; posted 11/14/2014; Doc. ID 220848
  • [full text: PDF (6781) KB)]
  • Abstract: We have analyzed the influence of the temporal pulse shape on femtosecond laser-induced surface ablation processes in Sapphire. To this end, single transform-limited (TL), stretched (ST) and third-order-dispersion (TOD) shaped femtosecond pulses have been used, while the dynamics of the interaction was analyzed by fs-resolved microscopy and correlated with the plasma emission intensity and crater morphology. The modification of the pulse shape enables changing the ablation mechanism from a strong, thermally-mediated ablation process to a gentle ablation process mediated by Coulomb explosion (CE), with respective ablation depths of 100-200 nm and 5-10 nm. The analysis of the transient optical response allows a direct comparison of the transient plasma carrier densities involved, observing comparable peak values for both processes. While for strong ablation induced by TL-pulses, a direct relation between plasma density and local ablation depth is found, this does not hold for the CE-mediated process observed for TOD-shaped pulses. For TOD-shaped pulses at very high fluence, a different ablation mechanism involving explosive boiling is identified. This mechanism leads to the formation of deep craters with reduced lateral extension and steep walls. This amount of control over the ablation mechanisms by a simple selection of the pulse shape should be of interest for new surface structuring approaches.

Keywords (OCIS):

  • (140.3390) Lasers and laser optics : Laser materials processing
  • (140.3440) Lasers and laser optics : Laser-induced breakdown
  • (300.2140) Spectroscopy : Emission
  • (320.5540) Ultrafast optics : Pulse shaping
  • (320.7120) Ultrafast optics : Ultrafast phenomena
  • (240.6648) Optics at surfaces : Surface dynamics

Mapping of Transmission Spectrum between Plasmonic and Non-plasmonic Single Slit I: Resonant Transmission

  • Shih-Hui Chang and Yu-Lun Su
  • received 08/07/2014; accepted 11/08/2014; posted 11/10/2014; Doc. ID 220538
  • [full text: PDF (951) KB)]
  • Abstract: In contrast to conventional emphases on plasmonic effects, similar transmission properties between a plasmonic and non-plasmonic 2D single slit are demonstrated in a series of two papers. In the first paper, a special case of resonant transmissions and the underlying physics of the similarities are explored. Extension to non-resonant transmission and the general transformation are discussed in the second paper. At resonant transmission, plasmonic and non-plasmonic single slits exhibit similar far-field and near-field properties at their corresponding resonant wavelengths. Their resonant transmission wavelengths can be transformed via a simple mapping with surface plasmon dispersion relation. Revisit of the Babinet’s principle implies that localized surface plasmon resonances play no role in the enhanced transmission of a 2D single slit. Fabry-Perot resonance, funneling at slit end faces and waveguide dispersion dominate the enhanced resonant transmission properties. Furthermore, an illusive optical property of a plasmonic slit can be achieved by a non-plasmonic slit via dimension scaling.

Keywords (OCIS):

  • (230.7400) Optical devices : Waveguides, slab
  • (240.6680) Optics at surfaces : Surface plasmons
  • (310.6805) Thin films : Theory and design

Mapping of Transmission Spectrum between Plasmonic and Non-plasmonic Single Slit II : Non-resonant Transmission

  • Shih-Hui Chang and Yu-Lun Su
  • received 08/07/2014; accepted 11/08/2014; posted 11/10/2014; Doc. ID 220539
  • [full text: PDF (971) KB)]
  • Abstract: In our previous work, the similarity in resonant transmission properties for plasmonic and non plasmonic 2D single slits can be realized by mapping their resonant wavelengths through waveguide dispersion. To further extend the mapping for non-resonant condition, complex reflection and transmission coefficients at the end faces of a semi-infinite slit are analyzed to reconstruct the whole spectra. These coefficients normalized by the waveguide mode (WGM) power are found identical at the same effective wavelength for both plasmonic and non-plasmonic cases. The reconstructed spectrum by a Fabry-Perot model matches the WGM-normalized transmission spectrum of a non-plasmonic slit and can be transformed into that of a plasmonic case by wavelength stretching with plasmonic waveguide dispersion. The normalized transmission power is bounded by 1+(λ/πd). Width-dependent red shifts of the transmission spectrum are associated with effective capacitances at the slit end faces. Same mapping method applies for a single slit with substrate and periodic case. Finally the focusing lens effect of a plasmonic slit array can be mimicked by a non-plasmonic slit array with dimension scaling. The unified transmission properties of plasmonic and non-plasmonic 2D single slits can simplify the design of slit structures for plasmonic applications.

Keywords (OCIS):

  • (230.7400) Optical devices : Waveguides, slab
  • (240.6680) Optics at surfaces : Surface plasmons
  • (310.6805) Thin films : Theory and design

Second harmonic generation from metallic arrays of rectangular holes

  • Sergio G. Rodrigo, V. Laliena, and L. Martin-Moreno
  • received 08/28/2014; accepted 11/08/2014; posted 11/10/2014; Doc. ID 221783
  • [full text: PDF (3978) KB)]
  • Abstract: The generation process of second harmonic radiation from holes periodically arranged on a metal surface is investigated. Three main modulating factors aecting the far-field distribution and the transmission eciency are identified: the near-field distribution at the wavelength of the driving source (fundamental harmonic), how second harmonic light couples to the diraction orders of the lattice and its propagation properties inside the holes. It is shown that light generated at second harmonic can excite electromagnetic modes otherwise unac- cessible in the linear regime under normal incidence illumination, a singularity of second harmonic fields that aects the radiation process. For instance, the least decaying transversal electric TE0;1 mode accessible to the external beam is able to generate a superposition of high order modes (TE1;1 and TM1;1) at second harmonic. It is demonstrated that the emission of second harmonic radiation is only allowed along o-normal paths precisely due to that symmetry. In this work, two dierent regimes are studied in the context of extraordinary optical transmission, where enhanced linear transmission either occurs through localized electromagnetic modes or is aided by surface plasmon polaritons. While localized resonances in metallic hole arrays have been previously investigated, the role played by surface plasmons in second harmonic generation has not been addressed so far. In general, good agreement is found between our calculations (based on the finite dierence time domain method) and the experimental results on localized resonances, even though no free fitting parameters were used in describing the materials. It is found that second harmonic emission is strongly modulated by enhanced fields at the fundamental wavelength (either localized or surface plasmon modes) on the glass-metal interface. This is so in the transmission side but also in re ection, where emission can only be explained by an ecient tunneling of second harmonic photons through the holes from the output to the input side. Finally, the existence of a dark surface plasmon polariton at the fundamental field is identified through a non-invasive method for the first time, by analyzing the eciency and far-field pattern distribution in transmission at second harmonic.

Keywords (OCIS):

  • (050.1960) Diffraction and gratings : Diffraction theory
  • (160.4330) Materials : Nonlinear optical materials
  • (190.2620) Nonlinear optics : Harmonic generation and mixing
  • (240.6680) Optics at surfaces : Surface plasmons
  • (160.4236) Materials : Nanomaterials
  • (050.6624) Diffraction and gratings : Subwavelength structures

Ultra-widely tunable OPOs based on Relaxed Phase Matching – theoretical analysis

  • Quentin Clement, Jean-Michel Melkonian, Myriam Raybaut, Jean-Baptiste Dherbecourt, Antoine Godard, Benoit Boulanger, and Michel Lefebvre
  • received 09/15/2014; accepted 11/04/2014; posted 11/06/2014; Doc. ID 222688
  • [full text: PDF (933) KB)]
  • Abstract: We present a thorough study of sub-millimeter long OPOs, also known as sheet-like OPOs (SOPO). We explain how the phase matching condition can be relaxed to enable ultra-wide tuning. Owing to a theoretical formalism based on integer modal numbers, we derive the conditions for double resonance and thus predict the emission spectrum of the doubly resonant SOPO. Our approach allows us to straightforwardly model several tuning methods based on pump wavelength, cavity length and crystal temperature. The calculations are compared with previously reported experimental results.

Keywords (OCIS):

  • (190.4410) Nonlinear optics : Nonlinear optics, parametric processes
  • (190.4970) Nonlinear optics : Parametric oscillators and amplifiers

Measuring principal modes in a multimode optical fiber using the mode dependent signal delay method

  • Giovanni Milione, Daniel Nolan, and Robert Alfano
  • received 07/18/2014; accepted 11/03/2014; posted 11/04/2014; Doc. ID 216296
  • [full text: PDF (551) KB)]
  • Abstract: A method to determine principle modes in a multimode optical fifiber is described. This method is referred to as the mode dependent signal delay method and is an extension of the analogous method to determine principal states of polarization in a single mode optical fifiber. In the mode dependent signal delay, principal modes can be determined by measuring N²-1 mean signal time delays at the output of a multimode optical fifiber for N²-1 linear combinations of modes launched at the input of the optical fifiber. The derivation of principal modes as eigenstates to a mode dispersion operator is reviewed. It is shown the mode dispersion operator is Hermitian and can be expanded by the N²-1 generators of the Lie algebra of the Lie group SU(N) which leads to a corresponding mode dispersion vector in an N²-1 dimensional Stokes space. Finally, using these results, the mean signal time delay of a light pulse at the output of a multimode optical fifiber is derived from which the mode dependent signal delay method is described. The differences between the mode dependent signal delay method and the analogous method in a single mode optical fifiber are discussed.

Keywords (OCIS):

  • (030.4070) Coherence and statistical optics : Modes
  • (060.0060) Fiber optics and optical communications : Fiber optics and optical communications
  • (060.4230) Fiber optics and optical communications : Multiplexing
  • (260.5430) Physical optics : Polarization
  • (070.6120) Fourier optics and signal processing : Spatial light modulators

Numerical study on the minimum modulation depth of a saturable absorber for stable fiber laser mode-locking

  • Jinwoo Jeon, Junsu Lee, and Ju Han Lee
  • received 09/19/2014; accepted 11/03/2014; posted 11/04/2014; Doc. ID 223451
  • [full text: PDF (607) KB)]
  • Abstract: We conducted a numerical study to investigate the minimum modulation depth of a saturable absorber that is essentially required for stable optical pulses to be generated from a passively mode-locked fiber laser cavity. More specifically, an extended nonlinear Schrödinger equation was numerically solved in order to analyze the impact of the cavity group velocity dispersion (GVD), cavity χ(3) nonlinearity, and saturation gain of an active fiber on the minimum modulation depth that is required. The net cavity GVD is shown to significantly influence the required minimum modulation depth level of a saturable absorber. A cavity with little net anomalous dispersion is found to be readily mode-locked through the use of a saturable absorber with a very small amount of modulation depth. Furthermore, the reason for which a fiber laser cavity with a zero cavity GVD becomes unstable and needs a much higher modulation depth was investigated, and such a conditions was found to be associated with the fiber χ(3) nonlinearity. The minimum modulation depth is also shown to vary according to the saturation gain level of an active fiber.

Keywords (OCIS):

  • (140.3430) Lasers and laser optics : Laser theory
  • (140.3510) Lasers and laser optics : Lasers, fiber
  • (140.4050) Lasers and laser optics : Mode-locked lasers

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