Scintillation properties of a rectangular dark hollow beam
Yangjian Cai, Yan Zhang
JOURNAL OF MODERN OPTICS
56(4)
502507
(2009)

Journal
The scintillation properties of a rectangular dark hollow beam (DHB) in a weak turbulent atmosphere are investigated. Explicit expression for the onaxis scintillation index of a rectangular DHB is derived. It is found that the scintillation index value of a rectangular DHB can be smaller than that of Gaussian, elliptical Gaussian and rectangular flattopped beams in a weak turbulent atmosphere under certain conditions. Our results will be useful in longdistance freespace optical communications. The scintillation properties of a rectangular DHB are closely controlled by its initial beam parameters.
Optimizing antiStokes Raman scattering in gasfilled hollowcore
photonic crystal fibers
AntiStokes Raman scattering in gasfilled hollowcore photonic crystal fibers is discussed. It is shown that the efficient antiStokes generation observed under conditions of significant wave mismatch is caused by phase locking of the interacting fields. This leads to the establishment of a phase difference that is independent of the optical path. An optimization technique, based on the adjustment of the wave mismatch along a gasfilled hollow fiber using pressure control, is proposed. AntiStokes conversion efficiencies close to the theoretical maximum of 50% are predicted.
Reduction of Nonlinear Phase Noise in DPSK Transmission Using a NALM
C. Stephan, K. Sponsel, G. Onishchukov, B. Schmauss, G. Leuchs
2009 IEEE/LEOS WINTER TOPICALS MEETING SERIES (WTM 2009)
209210
(2009)
Performance of a NALM as phasepreserving amplitude 2Rregenerator in a DPSK transmission system has been investigated experimentally and numerically. A 3dB improvement of eye opening or alternatively a 3dB increase of fibrelaunched power are demonstrated.
A vibrationinsensitive optical cavity and absolute determination of its
ultrahigh stability
Y. N. Zhao, J. Zhang, A. Stejskal, T. Liu, V. Elman, Z. H. Lu, L. J. Wang
We use the threecorneredhat method to evaluate the absolute frequency stabilities of three different ultrastable reference cavities, one of which has a vibrationinsensitive design that does not even require vibration isolation. An Nd: YAG laser and a diode laser are implemented as light sources. We observe similar to 1 Hz beat note linewidths between all three cavities. The measurement demonstrates that the vibrationinsensitive cavity has a good frequency stability over the entire measurement time from 100 mu s to 200 s. An absolute, correlationremoved Allan deviation of 1.4 x 10(15) at 1 s of this cavity is obtained, giving a frequency uncertainty of only 0.44 Hz. (C) 2009 Optical Society of America
Continuous Variable Entanglement and Squeezing of Orbital Angular
Momentum States
We report the first experimental characterization of the firstorder continuous variable orbital angular momentum states. Using a spatially nondegenerate optical parametric oscillator (OPO) we produce quadrature entanglement between the two firstorder LaguerreGauss modes. The family of orbital angular momentum modes is mapped on an orbital Poincare sphere, where the mode's position on the sphere is spanned by the three orbital parameters. Using a nondegenerate OPO we produce squeezing of these parameters, and as an illustration, we reconstruct the "cigarshaped" uncertainty volume on the orbital Poincare sphere.
Solitary Pulse Generation by Backward Raman Scattering in H2Filled
Photonic Crystal Fibers
A. Abdolvand, A. Nazarkin, A. V. Chugreev, C. F. Kaminski, P. St. J. Russell
Using a hydrogenfilled hollowcore photonic crystal fiber as a nonlinear optical gas cell, we study amplification of nslaser pulses by backward rotational Raman scattering. We find that the amplification process has two characteristic stages. Initially, the pulse energy grows and its duration shortens due to gain saturation at the trailing edge of the pulse. This phase is followed by formation of a symmetric pulse with a duration significantly shorter than the phase relaxation time of the Raman transition. Stabilization of the Stokes pulse profile to a solitonlike hyperbolic secant shape occurs as a result of nonlinear amplification at its front edge and nonlinear absorption at its trailing edge (caused by energy conversion back to the pump field), leading to a reshaped pulse envelope that travels at superluminal velocity.
Correlation measurement of squeezed light
Leonid A. Krivitsky, Ulrik L. Andersen, Ruifang Dong, Alexander Huck, Christoffer Wittmann, Gerd Leuchs
We study the implementation of a correlation measurement technique for the characterization of squeezed light which is nearly free of electronic noise. With two different sources of squeezed light, we show that the sign of the covariance coefficient, revealed from the timeresolved correlation data, is witnessing the presence of squeezing in the system. Furthermore, we estimate the degree of squeezing using the correlation method and compare it to the standard homodyne measurement scheme. We show that the role of electronic detector noise is minimized using the correlation approach as opposed to homodyning where it often becomes a crucial issue.
A method to unmix multiple fluorophores in microscopy images with
minimal a priori information
S. Schlachter, S. Schwedler, A. Esposito, G. S. Kaminski Schierle, G. D. Moggridge, C. F. Kaminski
The ability to quantify the fluorescence signals from multiply labeled biological samples is highly desirable in the life sciences but often difficult, because of spectral overlap between fluorescent species and the presence of autofluorescence. Several so called unmixing algorithms have been developed to address this problem. Here, we present a novel algorithm that combines measurements of lifetime and spectrum to achieve unmixing without a priori information on the spectral properties of the fluorophore labels. The only assumption made is that the lifetimes of the fluorophores differ. Our method combines global analysis for a measurement of lifetime distributions with singular value decomposition to recover individual fluorescence spectra. We demonstrate the technique on simulated datasets and subsequently by an experiment on a biological sample. The method is computationally efficient and straightforward to implement. Applications range from histopathology of complex and multiply labelled samples to functional imaging in live cells. (C) 2009 Optical Society of America
Demonstration of a universal oneway quantum quadratic phase gate
Yoshichika Miwa, Junichi Yoshikawa, Peter van Loock, Akira Furusawa
We demonstrate a quadratic phase gate for oneway quantum computation in the continuousvariable regime. This canonical gate, together with phasespace displacements and Fourier rotations, completes the set of universal gates for realizing any singlemode Gaussian transformation such as arbitrary squeezing. As opposed to previous implementations of measurementbased squeezers, the current gate is fully controlled by the local oscillator phase of the homodyne detector. Verifying this controllability, we give an experimental demonstration of the principles of oneway quantum computation over continuous variables. Moreover, we can observe subshotnoise quadrature variances in the output states, confirming that nonclassical states are created through cluster computation.
Experimental observation of spectral Bloch oscillations
Christoph Bersch, Georgy Onishchukov, Ulf Peschel
OPTICS LETTERS
34(15)
23722374
(2009)
We report on the first, to our knowledge, experimental observation of spectral Bloch oscillations in an optical fiber employing the interaction between a probe signal and a travelingwave periodic potential. The spectrum of weak probe pulses is shown to oscillate on account of their groupvelocity mismatch to the periodic field. The behavior of a cw probe spectrum reveals the actual discrete nature of the effect. Recurrences of the spectrum after one and two Bloch periods are demonstrated. (C) 2009 Optical Society of America
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