Simultaneously measuring two ultrashort laser pulses on a single shot using “Double Blind Frequency-Resolved Optical Gating”

• Tsz Chun Wong, Justin Ratner, Vikrant Chauhan, Jacob Cohen, Peter Vaughan, Lina Xu, Antonio Consoli, and Rick Trebino
• received 11/22/2011; accepted 02/02/2012; posted 02/02/2012; Doc. ID 158454
• [full text: PDF (1818) KB)]
• Abstract: We demonstrate a simple self-referenced single-shot method for simultaneously measuring two different arbitrary pulses, which can potentially be complex and also have very different wavelengths. The method is a variation of cross-correlation frequency-resolved optical gating (XFROG) that we call “Double Blind” (DB) FROG. It involves measuring two spectrograms, both of which are obtained simultaneously in a single apparatus. DB FROG retrieves both pulses robustly by using the standard XFROG algorithm, implemented alternately on each of the traces, taking one pulse to be “known” and solving for the other. We show both theoretically and experimentally that DB FROG using a polarization-gating beam geometry works reliably and appears to have no nontrivial ambiguities.

Keywords (OCIS):

• (320.0320) Ultrafast optics : Ultrafast optics
• (320.7100) Ultrafast optics : Ultrafast measurements

Calculation of waveguide modes in linear chains of metallic nanorods

• Christos Tserkezis and Nikolaos Stefanou
• received 01/13/2012; accepted 01/31/2012; posted 02/02/2012; Doc. ID 161523
• [full text: PDF (3685) KB)]
• Abstract: We report on the calculation of the fundamental plasmon waveguide modes in linear periodic chains of finite silver nanorods, aligned perpendicular to the chain. The results of rigorous full-electrodynamic calculations by the layer-multiple-scattering method are discussed in conjunction with the results of the widely used coupled-dipole model and a critical evaluation of the latter is provided. More specifically, it is shown that both diameter and height of the nanorods must be much smaller than the interparticle distance; otherwise, for relatively long nanorods close to each other, the coupled-dipole model can fail completely to predict the waveguide dispersion diagram. Moreover, the model systematically underestimates the effect of dissipative losses and cannot describe the effect of a supporting substrate, which is always present in realistic cases and induces considerable changes in the waveguide dispersion diagram.

Keywords (OCIS):

• (130.3130) Integrated optics : Integrated optics materials
• (230.7370) Optical devices : Waveguides
• (250.5403) Optoelectronics : Plasmonics

Optical self-trapping in a photopolymer doped with Ag nanoparticles: a single-step route to metallodielectric cylindrical waveguides

• Liqun Qiu and Kalaichelvi Saravanamuttu
• received 11/28/2011; accepted 01/31/2012; posted 01/31/2012; Doc. ID 158802
• [full text: PDF (1437) KB)]
• Abstract: A continuous wave, visible laser beam self-traps by initiating free-radical polymerization in an organosiloxane photopolymer doped with a well-characterised distribution of Ag nanoparticles. The self-trapped beam propagates over long distances (>> Rayleigh range) without diverging and permanently inscribes a cylindrical metallodielectric waveguide containing a dispersion of Ag nanoparticles. The self-trapped beam evolves from single-mode to multimode guidance over time; the effects of nanoparticle concentration on multimode dynamics were investigated. These findings open room temperature, soft polymer-based pathways where self-action effects including self-trapping and modulation instability can be exploited to spontaneously generate 3-D metallodielectric of single or multiple cylindrical waveguides.

Keywords (OCIS):

• (160.3900) Materials : Metals
• (160.5470) Materials : Polymers
• (190.5940) Nonlinear optics : Self-action effects

Photoluminescence of lithium thiogallate LiGaS2

• Alexander Yelisseyev, Marina Starikova, Valery Korolev, Ludmila Isaenko, and Sergey Lobanov
• received 11/14/2011; accepted 01/31/2012; posted 02/02/2012; Doc. ID 157264
• [full text: PDF (2097) KB)]
• Abstract: Annealing in appropriate atmosphere affects considerably transparency and photo luminescence (PL) of lithium thiogallate LiGaS2 (LGS). Intense violet to blue PL in 2.74 and 2.986 eV bands appears after vacuum annealing or irradiation: PL is associated with two types of crystallographically nonequivalent anion vacancies (F-centers). The 2.986 eV emission of more stable center decays exponentially with decay times τ =19 μsec и 218 nsec at 80 and 300 K, respectively and quenches to 650 K. PL in a 2.0 eV band, excited near the fundamental absorption edge, with a large Stokes shift and fast temperature quenching is related to recombination of the self-trapped excitons. LGS with F-centers can be used as a light-emitting medium in different laser and optoelectronic devices.

Keywords (OCIS):

• (140.3380) Lasers and laser optics : Laser materials
• (300.6250) Spectroscopy : Spectroscopy, condensed matter
• (300.6280) Spectroscopy : Spectroscopy, fluorescence and luminescence

Optimizing the design of planar heterostructures for plasmonic waveguiding

• Dayan Handapangoda, Ivan Rukhlenko, and Malin Premaratne
• received 10/28/2011; accepted 01/30/2012; posted 01/31/2012; Doc. ID 157323
• [full text: PDF (372) KB)]
• Abstract: We theoretically investigate planar heterostructures for subwavelength guiding of surface plasmon modes and optimize their design to enhance the waveguiding efficiency. We show that by appropriately selecting the thicknesses of metallic and dielectric layers of a two-layer waveguide, one can compensate the intrinsic damping of the mode by having minimal optical gain in the dielectric region. We also reveal that mode confinement can be significantly improved by the use of an additional metal layer adjacent to the dielectric, to form a metal–dielectric–metal(MDM) structure. By varying the layer thicknesses in the MDM waveguide, we demonstrate that the propagation length of the plasmonic mode can be maximized. We further show that the losses may be suppressed by minimal gain in the dielectric region by the careful choice of geometrical parameters. We note that the associated gain levels are relatively small, for example, the losses in a 300 nm-thick Ag–ZnO–Ag waveguide can be compensated by a gain of ∼ 110 cm−1. Our results may prove useful for the realization of efficient optical interconnects in high-density nanophotonic circuity.

Keywords (OCIS):

• (230.7390) Optical devices : Waveguides, planar
• (240.6680) Optics at surfaces : Surface plasmons
• (250.5403) Optoelectronics : Plasmonics

Dispersion relations in metal nano-particle chains: Necessity of the multipole approach

• Brice Rolly, Nicolas Bonod, and Brian Stout
• received 12/13/2011; accepted 01/30/2012; posted 02/02/2012; Doc. ID 159722
• [full text: PDF (315) KB)]
• Abstract: Lorenz-Mie multiple-scattering theory is used to perform quasi-exact calculations of the lossy dispersion relations of propagating modes in infinite chains of metallic spheres. Lossy modes are described by allowing the projection of the wave vector along the chain axis to be a complex number rather than the more common complex frequency description. We show that even when the constituent particles are much smaller than the wavelength, one generally needs to go well beyond the coupled dipole approximation to achieve stable predictions.

Keywords (OCIS):

• (230.7370) Optical devices : Waveguides
• (290.4020) Scattering : Mie theory
• (290.4210) Scattering : Multiple scattering
• (250.5403) Optoelectronics : Plasmonics
• (290.5825) Scattering : Scattering theory

Fast and effective implementation of discrete quantum Fourier transform via virtual-photon-induced process in separate cavities

• Hong-Fu Wang, Shou Zhang, Ai-Dong Zhu, X. X. Yi, and Kyu-Hwang Yeon
• received 12/13/2011; accepted 01/28/2012; posted 02/02/2012; Doc. ID 159837
• [full text: PDF (333) KB)]
• Abstract: We present a fast and effective scheme to implement multi-qubit discrete quantum Fourier transform for distant atoms trapped in separate cavities connected by optical fibers via virtual-photon-induced process. The effective coupling between two distributed atoms is achieved without exciting and transporting photons through the optical fiber and the gate operation is robust against the decoherence effect when the thermal photons in the environment are negligible. The implementation of the scheme is appealingly simple because the complex combination of quantum gate operations, which act on each two qubits in the rearranged discrete quantum Fourier transform circuit, are achieved only in one step through the interaction controlled by optical switches between two adjacent cavities. The scheme opens promising perspectives for scalable quantum communication networks and distributed quantum computation.

Keywords (OCIS):

• (270.0270) Quantum optics : Quantum optics
• (270.5585) Quantum optics : Quantum information and processing

Spatio-temporal phasematching in capillary high-harmonic generation

• Edward Rogers, Sarah Stebbings, Ana de Paula, Christopher Froud, Matthew Praeger, Benjamin Mills, James Grant-Jacob, William Brocklesby, and Jeremy Frey
• received 07/11/2011; accepted 01/26/2012; posted 01/27/2012; Doc. ID 150928
• [full text: PDF (450) KB)]
• Abstract: We present a simple phasematching model that takes into account the full spatio-temporal nature of capillary high-harmonic generation. Spectra predicted from the model are compared to experimental results for a number of gases and are shown to reproduce the spectral envelope of experimentally generated harmonics. The model demonstrates that an ionisation-induced phase mismatch is limiting the cutoff energy of current capillary high-harmonic generation experiments. The success of this model shows that phasematching processes play a dominant role in determining the emission from capillary high-harmonic generation.

Keywords (OCIS):

• (190.7110) Nonlinear optics : Ultrafast nonlinear optics
• (320.7110) Ultrafast optics : Ultrafast nonlinear optics
• (020.2649) Atomic and molecular physics : Strong field laser physics
• (260.6048) Physical optics : Soft x-rays

Characteristics of defect modes in side-coupled and mutually-coupled microresonator arrays

• Landobasa Tobing, Liliana Tjahjana, and Dao Hua Zhang
• received 11/22/2011; accepted 01/24/2012; posted 01/24/2012; Doc. ID 158406
• [full text: PDF (788) KB)]
• Abstract: We present both theoretically and experimentally the existence of defect modes in side-coupled and mutually-coupled microresonator arrays. The qualitative difference between the two types of defect modes is investigated. The Q-factor of both defect modes for varying defect sizes is characterized and shown to generate Q enhancement of ~30x relative to individual loaded resonators. The defect modes are then compared with coupled resonator induced transparency (CRIT), from which it can be shown that the defect modes based on side-coupled microresonator arrays are actually the extension of the CRIT-resonance in two-resonator structure.

Keywords (OCIS):

• (130.0130) Integrated optics : Integrated optics
• (230.4555) Optical devices : Coupled resonators

Comparison between Spectral Optical Coherence Tomography and the FFT-based Impulse Response Reconstruction Method in the transmission configuration

• Yaron Levy, Er'el Granot, and Shmuel Sternklar
• received 10/06/2011; accepted 01/23/2012; posted 01/24/2012; Doc. ID 156085
• [full text: PDF (481) KB)]
• Abstract: We present a comparison between the well-known Spectral Optical Coherence Tomography (SOCT) technology and the FFT-based Impulse Response Reconstruction Method (FIRRM) which we developed – both in the transmission configuration. It is shown that since the transmission configuration requires relatively long interferometers, the SOCT measurements are less stable than those of the FIRRM, as seen in the impulse response reconstruction of the two methods. FIRRM results show much better agreement with theoretical predictions.

Keywords (OCIS):

• (290.1990) Scattering : Diffusion
• (110.0113) Imaging systems : Imaging through turbid media

Analysis of light wave diffraction and amplification by reflection grating operating in the second-order Bragg regime. 1. Approximate theory

• Volodymyr Fitio and T. Smirnova
• received 09/22/2011; accepted 01/23/2012; posted 01/24/2012; Doc. ID 155073
• [full text: PDF (397) KB)]
• Abstract: A new approximate theory was developed and applied to analysis of the second-order Bragg diffraction by a thick reflection grating formed in a medium with and without optical gain. To derive the general system of equations describing the optical wave interaction with a grating the method of constant variation was used that allowed obtaining the analytical formulas for the electric-field strength of transmitted and reflected wave. The proposed approach was extended to the case of grating formed in a material with nonlinear response to the recording field when dielectric permittivity modulation of a medium includes higher spatial harmonics.

Keywords (OCIS):

• (050.1960) Diffraction and gratings : Diffraction theory
• (140.3490) Lasers and laser optics : Lasers, distributed-feedback

Propagation of vectorial laser beams

• Peter Muys
• received 12/19/2011; accepted 01/23/2012; posted 01/27/2012; Doc. ID 159962
• [full text: PDF (302) KB)]
• Abstract: The angular spectrum of a vectorial laser beam is expressed in terms of an intrinsic coordinate system instead of the usual Cartesian laboratory coordinates. This switch leads to simple, elegant and new expressions such as for the angular spectrum of the Hertz vectors corresponding to the electromagnetic fields. As an application of this approach, we consider axially symmetric vector beams, showing non-diffracting properties of these beams, without invoking the paraxial approximation.

Keywords (OCIS):

• (260.1960) Physical optics : Diffraction theory
• (260.5430) Physical optics : Polarization

Excitation of multiple surface-plasmon-polariton waves guided by the periodically corrugated interface of a metal and a periodic multi-layered isotropic dielectric material

• Muhammad Faryad, Anthony Hall, Greg Barber, Thomas Mallouk, and Akhlesh Lakhtakia
• received 12/21/2011; accepted 01/23/2012; posted 01/24/2012; Doc. ID 160421
• [full text: PDF (631) KB)]
• Abstract: The excitation of multiple surface-plasmon-polariton (SPP) waves guided by the periodically corrugated interface of a homogeneous metal and a periodic multi-layered isotropic dielectric (PMLID) material was studied theoretically. The solution of the underlying canonical boundary-value problem (with a planar interface) indicates that multiple SPP waves of different polarization states, phase speeds, and attenuation rates can be guided by the periodically corrugated interface. Accordingly, the boundary-value problem was formulated using rigorous coupled-wave analysis and solved using a numerically stable al- gorithm. A linearly polarized plane wave was considered obliquely incident on a PMLID material of finite thickness and backed by a metallic surface-relief grating. The total reflectance, total transmittance, and the absorptance were calculated as functions of the incidence angle for different numbers of unit cells in the PMLID material of fixed period. The excitation of SPP waves was indicated by those peaks in the absorptance curves that were independent of the number of unit cells and these peaks were also correlated with the solutions of a dispersion equation obtained from the canonical boundary-value problem.

Keywords (OCIS):

• (240.0310) Optics at surfaces : Thin films
• (240.6680) Optics at surfaces : Surface plasmons
• (240.6690) Optics at surfaces : Surface waves

Frequency Modulation Background Signals from Fiber-based Electro Optic Modulators are Caused by Crosstalk

• Isak Silander, Patrick Ehlers, Junyang Wang, and Ove Axner
• received 10/21/2011; accepted 01/18/2012; posted 01/18/2012; Doc. ID 156948
• [full text: PDF (547) KB)]
• Abstract: Frequency modulated spectroscopy (FMS) performed by the use of fiber-coupled electro optic modulators (FC-EOM) is often plagued by background signals that bring in noise and, by their temperature dependence, severe drifts. These signals cannot be zeroed out by the conventional technique of using a carefully adjusted polarizer that can be applied to free space EOMs. This can limit the use of FC-EOM in high performance detection techniques. Here we provide an explanation to these background signals that is based upon crosstalk between various polarization directions of light in the fixed mounted polarization-maintaining fibers and the electro optic crystal. The description provides a basis for the previously demonstrated technique that utilizes an EOM regulated simultaneously by temperature and DC voltage to eliminate background signals from systems encompassing FC-EOMs.

Keywords (OCIS):

• (060.2340) Fiber optics and optical communications : Fiber optics components
• (060.2630) Fiber optics and optical communications : Frequency modulation
• (130.3120) Integrated optics : Integrated optics devices
• (300.6310) Spectroscopy : Spectroscopy, heterodyne
• (300.6380) Spectroscopy : Spectroscopy, modulation
• (140.3518) Lasers and laser optics : Lasers, frequency modulated

Observation of magneto-optical effect in extremely dilute ferrofluids under weak magnetic field

• Jingjing Sun, Cheng Yin, Changping Zhu, Xianping Wang, Wen Yuan, Pingping Xiao, Xianfeng Chen, and Zhuangqi Cao
• received 12/09/2011; accepted 01/18/2012; posted 01/18/2012; Doc. ID 159752
• [full text: PDF (2007) KB)]
• Abstract: A novel liquid-core waveguide using water-based ferrofluids as the guiding layer in a symmetrical metal cladding waveguide (SMCW) structure was proposed to investigate the magneto-optical effect of extremely dilute ferrofluids. Owing to the high sensitivity of the ultra-high order modes, the reflection intensity can be effectively tuned even by a weak magnetic field and the modulated reflectivity exhibits no threshold behavior. Furthermore, by properly adjusting the transmission axes of the polarizer, the detected laser intensity can be magnetic field independent since the refractive index for ordinary and extraordinary rays vary oppositely under the external field.

Keywords (OCIS):

• (160.3820) Materials : Magneto-optical materials
• (230.7390) Optical devices : Waveguides, planar
• (310.6860) Thin films : Thin films, optical properties

Using a fiber stretcher as a fast phase modulator in a continuous-wave terahertz spectrometer

• Axel Roggenbuck, Komalavalli Thirunavukkuarasu, Holger Schmitz, Jennifer Marx, Anselm Deninger, Ivan Cámara Mayorga, Rolf Güsten, Joachim Hemberger, and Markus Grüninger
• received 12/06/2011; accepted 01/17/2012; posted 01/24/2012; Doc. ID 159508
• [full text: PDF (596) KB)]
• Abstract: Continuous-wave terahertz spectroscopy based on photomixing offers the attractive feature of detecting both amplitude and phase of the terahertz radiation. Experimentally, it is challenging to achieve sufficient accuracy at a high data acquisition rate. We use two fiber stretchers as fast phase modulators in a symmetric setup. The central advantage is that the fiber stretchers are rather fast compared to a mechanical delay stage. We achieve a stability of the optical path difference of around 10 μm and use low-doped Si as an example to demonstrate the performance of our spectrometer.

Keywords (OCIS):

• (060.5060) Fiber optics and optical communications : Phase modulation
• (120.6200) Instrumentation, measurement, and metrology : Spectrometers and spectroscopic instrumentation
• (300.6495) Spectroscopy : Spectroscopy, teraherz

Radiation Characteristics of Large-area Photomixer‎ Used for Generation of Continuous-Wave Terahertz Radiation‎

• Armaghan Eshaghi, Mahmoud Shahabadi, and Lukas Chrostowski
• received 12/21/2011; accepted 01/17/2012; posted 01/31/2012; Doc. ID 160274
• [full text: PDF (405) KB)]
• Abstract: Generation of 2-microwatt continuous-wave (CW) terahertz (THz) radiation at 1.2THz using a large-area photomixer with interdigitated electrodes is ‎reported.‎ ‎The‎‎ ‎structure‎‎ ‎of‎‎ ‎the‎‎ ‎utilized‎‎‎‎‎‎‎‎ ‎photomixer‎‎ ‎allows‎‎‎ ‎for‎‎‎‎‎ unidirectional carrier acceleration‎ ‎over‎‎ ‎the‎‎ ‎illuminated‎‎‎‎ ‎areas‎‎. ‎We determine the characteristics of the generated CW-THz beam and show that ‎the‎‎ divergence of this beam is dependent on the ‎spot‎ ‎size‎‎ of the pump beams focused on the large-area photomixer‎. ‎An‎ ‎illuminated‎‎ ‎area‎‎ with dimensions much larger than the THz ‎wavelength ‎helps ‎to‎‎‎ ‎eliminate‎‎ the focusing optics for the THz ‎beam‎‎‎. ‎Additionally‎, ‎we demonstrate that the THz beam radiated from the large-area photomixer is steerable by changing the incidence angles of the CW laser ‎beams,‎ ‎as‎‎ ‎a‎ ‎result‎‎ ‎of‎‎‎ ‎which‎‎ the phase distribution of the photocurrent along the contact stripes‎ ‎varies‎‎‎‎. ‎In ‎the‎‎ ‎proposed‎‎ experimental setup‎, ‎the ‎generated‎ THz beam is steerable in the range of -30 to +30 degrees‎.

Keywords (OCIS):

• (160.5140) Materials : Photoconductive materials
• (190.7070) Nonlinear optics : Two-wave mixing

Measurement of second-order nonlinear optical coefficients of BaMgF4

• Junjie Chen, Xianfeng Chen, Yanzhi Ma, Yuanlin Zheng, Anhua Wu, Hongjun Li, Linwen Jiang, and Jun Xu
• received 10/27/2011; accepted 01/16/2012; posted 01/17/2012; Doc. ID 157187
• [full text: PDF (805) KB)]
• Abstract: The three independent second-order nonlinear optical coefficients of BaMgF4 are determined by Maker fringe method with nanosecond pulsed Nd: YAG laser at 1064nm wavelength. All the results are relative to the reference crystal congruent LiNbO3. The largest element in second-order nonlinear optical matrix of BaMgF4 is d32 with the value of 0.36pm/V.

Keywords (OCIS):

• (140.3380) Lasers and laser optics : Laser materials
• (160.3380) Materials : Laser materials

Nonclassicality and decoherence of photon-added squeezed thermal state in thermal environment

• Li-yun Hu and Zhi-Ming Zhang
• received 11/22/2011; accepted 01/10/2012; posted 01/12/2012; Doc. ID 158587
• [full text: PDF (627) KB)]
• Abstract: Theoretical analysis is given of nonclassicality and decoherence of the field states generated by adding any number of photons to the squeezed thermal state (STS). Based on the fact that the squeezed number state can be considered as a single-variable Hermite polynomial excited state, the compact expression of the normalization factor is derived, a Legendre polynomial. The nonclassicality is investigated by exploring the sub-Poissonian and negative Wigner function (WF). The results show that the WF of single photon-added STS (PASTS) always has negative values at the phase space center. The decoherence effect on PASTS is examined by the analytical expression of WF. It is found that a longer threshold value of decay time is included in single PASTS than in single-photon subtraction STS.

Keywords (OCIS):

• (270.0270) Quantum optics : Quantum optics
• (270.6570) Quantum optics : Squeezed states

The role of pump coherence in the evolution of continuous-wave supercontinuum generation initiated by modulation instability

• E. J. R. Kelleher, J. C. Travers, S. V. Popov, and J. R. Taylor
• received 11/22/2011; accepted 01/09/2012; posted 01/13/2012; Doc. ID 158233
• [full text: PDF (3147) KB)]
• Abstract: We report in detail, both experimentally and using numerical simulation, the efficiency of generation of supercontinua in optical fiber driven by modulation instability of a continuous wave pump source. It is shown that the degree of pump coherence has a dramatic effect on the resulting spectral expansion and it is discussed how this can be explained by having the proper conditions for efficient modulation instability to break the continuous wave pump light into a train of fundamental solitons that subsequently undergo self-Raman shift to longer wavelengths. It is proposed that an optimal pump bandwidth exists corresponding to the optimal degree of pump incoherence, defined as a function of the modulation instability period.

Keywords (OCIS):

• (060.4370) Fiber optics and optical communications : Nonlinear optics, fibers
• (060.5530) Fiber optics and optical communications : Pulse propagation and temporal solitons
• (140.3510) Lasers and laser optics : Lasers, fiber
• (060.3510) Fiber optics and optical communications : Lasers, fiber