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December


Experimental verifications on an effective model for photonic coupling

  • Lei Zhou, Meng Qiu, Shiyi Xiao, Qiong He, and Shulin Sun
  • received 10/27/2014; accepted 12/04/2014; posted 12/16/2014; Doc. ID 225787
  • [full text: PDF (1455) KB)]
  • Abstract: Combining near-field measurements with coupled-mode-theory analyses, we unambiguously identify all resonant modes in coupled systems containing two photonic resonators. Based on this technique, we perform extensive microwave experiments to study how the inter-resonator coupling varies against various configurational parameters. Our experimental results quantitatively verify a previously established effective model for photonic coupling, and highlight the importance of quadrupole terms in certain situations.

Keywords (OCIS):

  • (230.5750) Optical devices : Resonators
  • (230.4555) Optical devices : Coupled resonators

High contrast imaging of reversibly switchable fluorescent proteins via temporally unmixed Multispectral Optoacoustic Tomography (tuMSOT)

  • Gil Westmeyer, Andre Stiel, Xose Luis Dean Ben, Yuanyuan Jiang, Daniel Razansky, and Vasilis Ntziachristos
  • received 09/29/2014; accepted 12/03/2014; posted 12/17/2014; Doc. ID 223208
  • [full text: PDF (399) KB)]
  • Abstract: Photocontrol of reversibly switching fluorescent proteins (RSFPs) was used to program optoacoustic signal time courses that were temporally unmixed to increase their contrast-to-noise-ratios (CNR) in optoacoustic imaging. In this way, two variants of the RSFP Dronpa with very similar optoacoustic spectra could be readily discriminated in the presence of highly absorbing blood. Addition of temporal unmixing to multispectral optoacoustic tomography (tuMSOT) in conjunction with synthetic and genetically controlled photochromic contrast agents and customized photocontrol-readout schemes can increase the performance of multiplexed and high contrast molecular optoacoustic imaging.

Keywords (OCIS):

  • (160.4670) Materials : Optical materials
  • (160.4760) Materials : Optical properties
  • (170.3010) Medical optics and biotechnology : Image reconstruction techniques
  • (170.5120) Medical optics and biotechnology : Photoacoustic imaging
  • (170.6920) Medical optics and biotechnology : Time-resolved imaging
  • (160.1435) Materials : Biomaterials

In-band-Pumped Ho:KLu(WO4)2 Microchip Laser With 84% Slope Efficiency

  • Xavier Mateos, Pavel Loiko, Josep Maria Serres, Konstantin Yumashev, Nikolai Kuleshov, Valentin Petrov, Uwe Griebner, Magdalena Aguiló, and Francesc Diaz
  • received 10/27/2014; accepted 12/03/2014; posted 12/16/2014; Doc. ID 225754
  • [full text: PDF (1964) KB)]
  • Abstract: We report on a continuous-wave Ho:KLu(WO4)2 (KLuW) microchip laser with a record slope efficiency of 84%, the highest value among the holmium inband-pumped lasers, delivering 201 mW output power at 2105 nm. The Ho laser operating at room temperature on the 5I8→5I7 transition is in-band-pumped by a diode-pumped Tm:KLuW microchip laser at 1946 nm. Ho:KLuW laser operation at 2061 and 2079 nm is also demonstrated with a maximum slope efficiency of 79%. The microchip laser generates an almost diffraction-limited output beam with a Gaussian profile and a M2 < 1.1. The laser performance of the Ng-cut Ho:KLuW crystal is very similar for pump light polarizations || Nm and Np. The positive thermal lens plays a key role in the laser mode stabilization and proper mode-matching. The latter, together with the low quantum defect under in-band-pumping (~0.08), is responsible for the extraordinary high slope efficiency.

Keywords (OCIS):

  • (140.3380) Lasers and laser optics : Laser materials
  • (140.3480) Lasers and laser optics : Lasers, diode-pumped
  • (140.5680) Lasers and laser optics : Rare earth and transition metal solid-state lasers
  • (140.6810) Lasers and laser optics : Thermal effects

Sub-diffuse interstitial optical tomography to improve the safety of brain needle biopsies: a proof-of-concept study

  • Andreanne Goyette, Julien Pichette, Marie-Andrée Tremblay, Audrey Laurence, Michael Jermyn, Kelvin Mok, Keith Paulsen, David Roberts, Kevin Petrecca, Brian Wilson, and Frederic Leblond
  • received 10/21/2014; accepted 12/03/2014; posted 12/08/2014; Doc. ID 224752
  • [full text: PDF (1060) KB)]
  • Abstract: The extraction of tissue samples during brain needle biopsy can cause life-threatening hemorrhage due to significant blood vessels injury during the procedure. Vessel rupture can have significant consequences for patient health, ranging from transient neurological deficits to death. Here, we present a sub-diffuse optical tomography technique that can be integrated into neurosurgical workflow to detect the presence of blood vessels. A proof-of-concept performed on a realistic brain tissue phantom is presented and demonstrates that interstitial optical tomography (iOT) can detect several 1 mm-diameter high-contrast absorbing objects located < 2 mm from the needle.

Keywords (OCIS):

  • (060.2350) Fiber optics and optical communications : Fiber optics imaging
  • (100.3010) Image processing : Image reconstruction techniques
  • (110.0110) Imaging systems : Imaging systems
  • (170.1610) Medical optics and biotechnology : Clinical applications

Strong triplet excited-state absorption in a phenanthrolinyl iridium(III) complex with benzothiazolylfluorenyl-substituted ligands

  • Timothy Pritchett, Michael Ferry, William Shensky, Andrew Mott, David Stewart, Stephanie Long, Joy Haley, Wenfang Sun, and Zhongjing Li
  • received 10/15/2014; accepted 12/03/2014; posted 12/08/2014; Doc. ID 224831
  • [full text: PDF (462) KB)]
  • Abstract: Femtosecond transient difference absorption (fs TA) measurements, together with a series of open-aperture Z scans at picosecond and nanosecond pulse widths and a variety of pulse energies were performed on a 1,10-phenanthrolinyl iridium(III) complex bearing ligands containing a benzothiazolylfluorenyl motif. An analysis of decay data from the fs TA experiment yields a value of 1.24 ± 0.26 ns for the singlet excited-state lifetime τS of the complex. By fitting the Z scans to a five-level dynamic model incorporating the independently measured value of τS and previously reported values of the complex’s triplet quantum yield (0.13) and triplet excited-state lifetime (230 ns), we obtain values of 3.5 × 10–17 cm² (singlet) and 5.0 × 10–16 cm² (triplet) for the excited-state absorption cross-sections of the complex in toluene solution at 532 nm; the latter value represents one of the largest triplet excited-state absorption cross sections ever reported at this wavelength. The ratio of the triplet excited-state cross section to the ground-state absorption cross section exceeds 3800.

Keywords (OCIS):

  • (160.4890) Materials : Organic materials
  • (190.4710) Nonlinear optics : Optical nonlinearities in organic materials

1.55 μm DFB laser monolithically integrated with amplifier array

  • Lianping Hou and John Marsh
  • received 10/03/2014; accepted 12/03/2014; posted 12/08/2014; Doc. ID 224344
  • [full text: PDF (1774) KB)]
  • Abstract: We present a laterally-coupled 1.55 μm distributed feedback laser monolithically integrated with multistage multi-mode interferences and semiconductor optical amplifiers, using low bias currents and providing an output power of ~100 mW with a quasi-single spatial mode far field pattern and low divergence angle of 3.5º in the horizontal direction. The fabrication techniques are based on side-wall gratings and quantum-well intermixing and offer a simple, flexible and low cost alternative to conventional methods.

Keywords (OCIS):

  • (140.3490) Lasers and laser optics : Lasers, distributed-feedback
  • (230.3120) Optical devices : Integrated optics devices
  • (250.5980) Optoelectronics : Semiconductor optical amplifiers

Mode switch based on electro-optic long-period waveguide grating in lithium niobate

  • Kin Chiang and Wei Jin
  • received 10/28/2014; accepted 12/03/2014; posted 12/11/2014; Doc. ID 225899
  • [full text: PDF (445) KB)]
  • Abstract: We propose a mode switch based on an electro-optic long-period grating formed in a lithium-niobate (LN) two-mode waveguide. Our fabricated device consists of an 8-mm-long grating in a proton-exchanged z-cut LN waveguide. At a driving voltage of 35 V, it can switch between the fundamental mode and the higher-order mode with a mode extinction ratio of -18 dB and a 3-dB bandwidth of ~25 nm at the wavelength 1544 nm. The performance of the device is insensitive to temperature variations. The experimental results agree well with the simulation. This mode switch could find applications in reconfigurable mode-division-multiplexing systems.

Keywords (OCIS):

  • (050.2770) Diffraction and gratings : Gratings
  • (130.3730) Integrated optics : Lithium niobate
  • (130.4815) Integrated optics : Optical switching devices

Experimental investigation on anticolliding-pulse mode-locked semiconductor lasers

  • Jun-Ping Zhuang, Vincenzo Pusino, Ding Ying, Sze-Chun Chan, and Marc Sorel
  • received 10/22/2014; accepted 12/03/2014; posted 12/11/2014; Doc. ID 225431
  • [full text: PDF (1209) KB)]
  • Abstract: We experimentally demonstrate anticolliding-pulse mode-locking (ACPML) in an integrated semiconductor laser. The device geometry consists of a gain section and a saturable absorber (SA) section located immediately next to one of the cavity facets. By depositing a low-reflection coating on the SA facet and a high-reflection coating on the gain section facet, the threshold is unchanged but the modulation of the SA is increased. The data presented here confirm that the ACPML configuration improves the output peak power of the pulses, reduces the amplitude fluctuation and timing jitter, and expands the biasing parameter range over which stable mode-locking operation occurs.

Keywords (OCIS):

  • (140.4050) Lasers and laser optics : Mode-locked lasers
  • (250.5960) Optoelectronics : Semiconductor lasers

Controlling the carrier-envelope phase of single-cycle pulses with two-color filamentation

  • Takao Fuji, Yutaka Nomura, Yu-Ting Wang, Atsushi Yabushita, Chih wei Luo, Yutaka Nomura, Chih wei Luo, Yu-Ting Wang, and Atsushi Yabushita
  • received 10/28/2014; accepted 12/03/2014; posted 12/08/2014; Doc. ID 219868
  • [full text: PDF (684) KB)]
  • Abstract: Carrier-envelope phase (CEP) of the single-cycle pulses generated through two-color filamentation has been investigated. We have observed a particular behavior of the phase, the phase of high frequency components of the generated pulses changes continuously and linearly with the relative phase between the two-color input pulses, whereas the phase of the low frequency components takes only two discrete values. The transition of the phase behavior has been clearly observed by using frequency-resolved optical gating capable of CEP determination. We have found out that such phase behavior is a unique feature of single-cycle pulses generated with a passive CEP stabilization scheme.

Keywords (OCIS):

  • (120.5050) Instrumentation, measurement, and metrology : Phase measurement
  • (320.7110) Ultrafast optics : Ultrafast nonlinear optics
  • (190.4975) Nonlinear optics : Parametric processes

Experimental demonstration of an SOI high performance double microring filter using MZI-based coupling

  • Robert Boeck, Michael Caverley, Lukas Chrostowski, and Nicolas Jaeger
  • received 09/05/2014; accepted 12/02/2014; posted 12/08/2014; Doc. ID 222495
  • [full text: PDF (433) KB)]
  • Abstract: We have experimentally demonstrated, in silicon, a double microring resonator with Mach-Zehnder interferometer-based coupling that meets many commercial specifications. Our device has a ripple of 0.5 dB, an adjacent channel isolation of at least 41.0 dB, a non-adjacent channel isolation of at least 38.6 dB, an interstitial peak suppression of at least 37.5 dB, an express channel isolation of 10.0 dB, and a free spectral range greater than the span of the C-band of 37.23 nm.

Keywords (OCIS):

  • (230.4555) Optical devices : Coupled resonators
  • (130.7408) Integrated optics : Wavelength filtering devices

Integrated in-fiber coupler for microsphere whispering gallery modes resonator excitation

  • Ruohui Wang, Michael Fraser, jiacheng Li, Xue-Guang Qiao, and Anbo Wang
  • received 11/07/2014; accepted 12/02/2014; posted 12/11/2014; Doc. ID 226395
  • [full text: PDF (581) KB)]
  • Abstract: We present an integrated in-fiber coupler for excitation of whispering-gallery modes of a microsphere resonator. The coupler is simply fabricated by chemical etching away the holey area of a photonic crystal fiber, leaving a free-standing solid core enclosed in a silica housing. Light is coupled into a microsphere through the suspended core with a diameter of 2.1μm. Since the coupler itself performs as a Fabry-Perot interferometer, asymmetric Fano resonances can be observed in the mixed reflection spectrum. The silica housing of the coupler provides a robust mechanical support to the microsphere resonator. The new Fano resonance coupler shows great potential in biochemical sensing and optical switching applications.

Keywords (OCIS):

  • (060.2310) Fiber optics and optical communications : Fiber optics
  • (230.3990) Optical devices : Micro-optical devices
  • (060.4005) Fiber optics and optical communications : Microstructured fibers
  • (070.5753) Fourier optics and signal processing : Resonators

Numerical modeling of Schell-model beams with arbitrary far-field patterns

  • David Voelz, Xifeng Xiao, and Olga Korotkova
  • received 11/13/2014; accepted 12/01/2014; posted 12/16/2014; Doc. ID 226795
  • [full text: PDF (568) KB)]
  • Abstract: An approach is described for creating random complex screens to be used in computer simulations of arbitrary Schell-model beams with a prescribed far-field intensity distribution. Simulation examples including beam profiles with reflection symmetry and rotational symmetry, flat-top, and pyramidal shapes are presented to verify the proposed approach. A more general scenario with a non-symmetric far-field beam shape is illustrated to demonstrate the field evolution in the free space propagation from the source plane to the far zone.

Keywords (OCIS):

  • (010.3310) Atmospheric and oceanic optics : Laser beam transmission
  • (030.1670) Coherence and statistical optics : Coherent optical effects
  • (030.6600) Coherence and statistical optics : Statistical optics
  • (140.3300) Lasers and laser optics : Laser beam shaping
  • (060.2605) Fiber optics and optical communications : Free-space optical communication

Influencing supercontinuum generation by phase distorting an ultrashort laser pulse

  • Aditya Dharmadhikari, Deepak Mathur, Jayashree Dharmadhikari, and Krithika Dota
  • received 11/18/2014; accepted 12/01/2014; posted 12/16/2014; Doc. ID 227127
  • [full text: PDF (559) KB)]
  • Abstract: We show that the spectral distribution of the supercontinuum generated in barium fluoride is amenable to alteration simply by controlling the second- and third-order phase distortion of incident femtosecond-duration pulses. The second- and third-order phase distortions are controlled by an acoustic-optic programmable dispersive filter (AOPDF). Spectral extent in the blue side of the SC is influenced by independently varying the phase distortion of an ultrashort laser pulse.

Keywords (OCIS):

  • (190.7110) Nonlinear optics : Ultrafast nonlinear optics
  • (230.1040) Optical devices : Acousto-optical devices
  • (320.1590) Ultrafast optics : Chirping
  • (320.5540) Ultrafast optics : Pulse shaping
  • (320.6629) Ultrafast optics : Supercontinuum generation

Fast bi-exponential fluorescence lifetime imaging analysis methods

  • David Li, Yu Chen, and Hongqi Yu
  • received 11/12/2014; accepted 12/01/2014; posted 12/02/2014; Doc. ID 226735
  • [full text: PDF (1648) KB)]
  • Abstract: A new hardware-friendly bi-exponential fluorescence lifetime imaging (FLIM) algorithm has been proposed. Compared to conventional FLIM software, the proposed algorithms are non-iterative offering direct calculation of lifetimes and therefore suitable for real-time applications. They can be applicable to single-channel or 2D multi-channel time-correlated single-photon counting (TCSPC) systems. The proposed methods have been tested on both synthesized and realistic FLIM data, and we have compared their performances with other recently proposed non-fitting bi-exponential techniques showing promising applications in future massive solid-state TCSPC imagers.

Keywords (OCIS):

  • (030.5260) Coherence and statistical optics : Photon counting
  • (110.0180) Imaging systems : Microscopy
  • (170.3650) Medical optics and biotechnology : Lifetime-based sensing
  • (170.6920) Medical optics and biotechnology : Time-resolved imaging
  • (040.1345) Detectors : Avalanche photodiodes (APDs)

Experimental investigation of phase-sensitive amplification of data signals in a 4-mode fiber-based PSA

  • André Albuquerque, Miguel Drummond, Rogerio Nogueira, Benjamin Puttnam, Jose Manuel Delgado Mendinueta, Satoshi Shinada, and Naoya Wada
  • received 09/25/2014; accepted 12/01/2014; posted 12/01/2014; Doc. ID 223811
  • [full text: PDF (368) KB)]
  • Abstract: In this letter we investigate the influence of the phase and power of pump and signal waves on the gain of a 4-mode phase-sensitive amplifier (PSA) built with a highly nonlinear fiber (HNLF), using a copier + PSA scheme to generate phase- and frequency-correlated idler. Using such an amplifier, low noise amplification of a 10 Gsymbol/s quadrature phase-shift keying (QPSK) signal with net gain of ~20 dB and less than 1 dB optical signal-to-noise ratio (OSNR) penalty at a bit error ratio (BER) of 10-3 were achieved. We also verified an additional net gain of 11.6 dB when switching from phase-insensitive to phase-sensitive operation, which is in good agreement with theoretical predictions of 12 dB.

Keywords (OCIS):

  • (060.0060) Fiber optics and optical communications : Fiber optics and optical communications
  • (060.2320) Fiber optics and optical communications : Fiber optics amplifiers and oscillators
  • (060.4370) Fiber optics and optical communications : Nonlinear optics, fibers
  • (190.0190) Nonlinear optics : Nonlinear optics
  • (190.4380) Nonlinear optics : Nonlinear optics, four-wave mixing
  • (190.4410) Nonlinear optics : Nonlinear optics, parametric processes

November


Multi-megagauss magnetic field generation by amplitude modulated surface plasma wave over a rippled metal surface

  • Pawan Kumar
  • received 10/07/2014; accepted 11/30/2014; posted 12/01/2014; Doc. ID 224482
  • [full text: PDF (367) KB)]
  • Abstract: The mechanism of self - generated megagauss magnetic field by an amplitude modulated surface plasma wave (SPW) over a rippled metallic surface is proposed. The amplitude modulated SPW exerts a ponderomotive force on free electrons in the metallic ripple, giving them an oscillatory velocity at the modulation frequency. The oscillatory velocity couples to the electron density in metallic ripple and drives a nonlinear current with . This irrotational nonlinear current generates the megagauss magnetic field.

Keywords (OCIS):

  • (190.4410) Nonlinear optics : Nonlinear optics, parametric processes
  • (240.4350) Optics at surfaces : Nonlinear optics at surfaces
  • (240.6680) Optics at surfaces : Surface plasmons
  • (240.6690) Optics at surfaces : Surface waves

Application of point diffraction interferometry for middle spatial frequency roughness detection

  • Michael Svechnikov, Nikolay Chkhalo, Michael Toropov, Nikolay Salashchenko, and Mariya Zorina
  • received 10/24/2014; accepted 11/30/2014; posted 12/01/2014; Doc. ID 225719
  • [full text: PDF (796) KB)]
  • Abstract: The possibilities of applying the point diffraction interferometry (PDI) method for the detection of the middle spatial frequency roughness of superpolished optical surfaces are analyzed. The roughness spectra obtained by both the PDI and atomic-force microscopy (AFM) methods are shown.

Keywords (OCIS):

  • (120.4800) Instrumentation, measurement, and metrology : Optical standards and testing
  • (120.6660) Instrumentation, measurement, and metrology : Surface measurements, roughness
  • (240.5770) Optics at surfaces : Roughness

Time multiplexing super resolution using Barker-based array

  • Asaf Ilovitsh, Zeev Zalevsky, Eyal Preter, and Nadav Levanon
  • received 11/05/2014; accepted 11/30/2014; posted 12/02/2014; Doc. ID 226364
  • [full text: PDF (706) KB)]
  • Abstract: We propose the use of a new encoding mask in order to improve the performance of the conventional time multiplexing super resolution method. The resolution improvement is obtained using a 2D Barker-based array which is placed upon the object, and shifted laterally. The Barker-based array is a 2D generalization of the standard 1D Barker code. The Barker-based array has stable auto-correlation sidelobes, making it ideal for the encoding process. A sequence of low resolution images are captured at different positions of the array, and are decoded properly using the same array. After removing the low resolution image from the resulting reconstruction, a high resolution image is established. The proposed method is presented analytically, demonstrated via numerical simulation, and validated by laboratory experiment.

Keywords (OCIS):

  • (100.0100) Image processing : Image processing
  • (100.6640) Image processing : Superresolution

Ultrafast oscilloscope based on laser-triggered field emitters

  • Brannon Klopfer, Seth Foreman, Thomas Juffmann, Mark Kasevich, Gunnar Skulason, and Catherine Kealhofer
  • received 11/05/2014; accepted 11/30/2014; posted 12/16/2014; Doc. ID 225953
  • [full text: PDF (398) KB)]
  • Abstract: Laser-triggered electron emission from sharp metal tips has been demonstrated in recent years as a high brightness ultrafast electron source, with possible applications ranging from ultrafast electron microscopy to laser-based particle accelerators to electron interferometry. The ultrafast nature of the emission process allows sampling of an instantaneous RF voltage applied to a field emitter. For a proof-of-concept, we use an RF signal derived from our laser's repetition rate, mapping a 9.28 GHz signal in 22.4 fs steps with 28 mV accuracy.

Keywords (OCIS):

  • (120.3930) Instrumentation, measurement, and metrology : Metrological instrumentation
  • (130.0250) Integrated optics : Optoelectronics
  • (320.2250) Ultrafast optics : Femtosecond phenomena
  • (320.7100) Ultrafast optics : Ultrafast measurements

Soliton Stability and Trapping in Multimode Fibers

  • Shaival Buch and Govind Agrawal
  • received 11/06/2014; accepted 11/30/2014; posted 12/08/2014; Doc. ID 226335
  • [full text: PDF (1406) KB)]
  • Abstract: We investigate stability of optical solitons in few-mode fibers by solving numerically coupled nonlinear Schrödinger equations that include intermodal nonlinear coupling. While a single fundamental soliton propagating in any fiber mode is stable, simultaneous propagation of two or more solitons in different fiber modes is not always stable and leads to interesting effects resulting from intermodal nonlinear coupling. Under some conditions, soliton trapping is observed such that two solitons in different modes shift their spectra and travel at the same speed in spite of considerable intermodal differential group delay between them.

Keywords (OCIS):

  • (060.4370) Fiber optics and optical communications : Nonlinear optics, fibers
  • (190.5530) Nonlinear optics : Pulse propagation and temporal solitons

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