We investigate the transmission of focused beams through single subwavelength holes in a silver film. We use radially and azimuthally polarized light to excite higher-order waveguide modes as well as to match the radial symmetry of the aperture geometry. Remarkably, the transmission properties can be described by a classical waveguide model even for thicknesses of the silver film as thin as a quarter of a wavelength.
Tailored polarization patterns for performance optimization of optical devices
In the case of strong focusing the smallest possible focal spot can be reached, provided one uses a specially designed polarization pattern. Other optical set-ups also employing high numerical aperture imaging are likewise expected to improve performance under polarization optimization. We propose a strategy for calculating the polarization pattern required for system optimization. A single element modulating only the polarization and not amplitude and phase may lead to satisfactory performance in some cases.
Experimental demonstration of macroscopic quantum coherence in Gaussian
states
Christoph Marquardt,
Ulrik L. Andersen,
Gerd Leuchs,
Yuishi Takeno,
Mitsuyoshi Yukawa,
Hidehiro Yonezawa,
Akira Furusawa
We witness experimentally the presence of macroscopic coherence in Gaussian quantum states using a recently proposed criterion [E. G. Cavalcanti and M. D. Reid, Phys. Rev. Lett. 97 170405 (2006)]. The macroscopic coherence stems from interference between macroscopically distinct states in phase space, and we prove experimentally that a coherent state contains these features with a distance in phase space of 0.51 +/- 0.02 shot noise units. This is surprising because coherent states are generally considered being at the border between classical and quantum states, not yet displaying any nonclassical effect. For squeezed and entangled states the effect may be larger but depends critically on the state purity.
Optimization of a nonlinear amplifying loop mirror for amplitude
regeneration in phase-shift-keyed transmission
Klaus Sponsel,
Kristian Cvecek,
Christian Stephan,
Georgy Onishchukov,
Bernhard Schmauss,
Gerd Leuchs
We present the numerical optimization of the transmission characteristics of a nonlinear amplifying loop mirror for amplitude regeneration of phase-encoded optical transmission formats. Adjusting the splitting factor, the amplifier gain and the phase bias, minimal phase distortions can be achieved while strong amplitude fluctuations are regenerated. The limiting effects of noise from the built-in amplifier and of amplified Rayleigh backscattering are also discussed.
Dynamic and steady state current response to light excitation of
multilayered organic photodiodes
E. S. Zaus,
S. Tedde,
J. Fuerst,
D. Henseler,
G. H. Doehler
JOURNAL OF APPLIED PHYSICS
101
(4)
044501
(2007)
| Journal
Measurements of current transients are used to gain insight into the mechanism of charge transport and extraction of photodiodes based on bulk heterojunction blends of poly-3-hexyl-thiophene and [6,6]-phenyl C-61 butyric acid methyl ester. It is shown that the implementation of an appropriate hole conducting layer leads to a reduction of the dark current in the reverse direction. It is observed that the dynamic response to light excitation is strongly influenced by the thickness of the hole conducting layer, the light intensity, and the applied bias. Charge accumulation at the interface is assumed to result in the characteristic shape of the transients. The shape of the switch-off transient can be understood qualitatively by an equivalent circuit diagram. (c) 2007 American Institute of Physics.
2R-regeneration of an RZ-DPSK signal using a nonlinear amplifying loop
mirror
K. Cvecek,
K. Sponsel,
G. Onishchukov,
B. Schmauss,
G. Leuchs
The performance of a nonlinear amplifying loop mirror as a 2R-regenerator for return-to-zero differential-phase-shift-keyed signals has been investigated experimentally. The measured power characteristics and phase functions show that the signal amplitude is regenerated while the signal phase is preserved in the setup. A significant eye-opening improvement and a negative power penalty of about 1.5 dB were obtained.
A new 4 pi geometry optimized for focusing on an atom with a dipole-like
radiation pattern
N. Lindlein,
R. Maiwald,
H. Konermann,
M. Sondermann,
U. Peschel,
G. Leuchs
Focusing electromagnetic radiation efficiently onto an atom requires an open geometry, which is as close to the full solid angle as possible. Additionally, the radiant intensity should be as close as possible to a dipole radiation in order to have a similar field distribution as in the emission process. Here, we propose to make use of a novel combination of a parabolic mirror and a diffractive optical element.
Generation of polarization squeezing with periodically poled KTP at 1064
nm
Mikael Lassen,
Metin Sabuncu,
Preben Buchhave,
Ulrik L. Andersen
We report the experimental demonstration of directly produced polarization squeezing at 1064 nm from a type I optical parametric amplifier (OPA) based on a periodically poled KTP crystal (PPKTP). The orthogonal polarization modes of the polarization squeezed state are both defined by the OPA cavity mode, and the birefringence induced by the PPKTP crystal is compensated by a second, but inactive, PPKTP crystal. Stokes parameter squeezing of 3.6 dB and anti squeezing of 9.4 dB is observed. (c) 2007 Optical Society of America.
Achieving Gaussian outputs from large-mode-area higher-order-mode fibers
We describe an alternative to fiber-gratings for converting higher-order LP0m (m > 1) fiber modes into a nearly fundamental Gaussian shape at the output of a fiber. This schematic enables the use of light propagation in higher-order modes of a fiber, a fiber-platform that has recently shown great promise for achieving very large mode areas needed for future high-power lasers and amplifiers. The conversion will be done by using a binary phase plate in the near field of the fiber, which emits the LP0m mode. Since the binary phase plate alone cannot increase the quality factor M-2 of the laser beam because of some broad sidebands, a filtering of the sidebands is done in the Fourier plane of a telescope. Of course, this will cost some of the total light power, but on the other side the M-2 factor can be reduced to nearly the ideal value near 1.0, and it is shown that similar to 76% of the total light power can be conserved for all investigated modes (2 <= m <= 8). A tolerance analysis for the phase plate and its adjustment is made, and different optical imaging systems to form a magnified image of the fiber mode on the phase plate are discussed in order to have more tolerance for the adjustment of the phase plate. (c) 2007 Optical Society of America.
Design of a mode converter for efficient light-atom coupling in free
space
M. Sondermann,
R. Maiwald,
H. Konermann,
N. Lindlein,
U. Peschel,
G. Leuchs
In this article, we describe how to develop a mode converter that transforms a plane electromagnetic wave into an inward-moving dipole wave. The latter one is intended to bring a single atom or ion from its ground state to an excited state by absorption of a single photon wave packet with near-100% efficiency.
2R-Regeneration of an 80-Gb/s RZ-DQPSK signal by a nonlinear amplifying
loop mirror
K. Cvecek,
K. Sponsel,
R. Ludwig,
C. Schubert,
C. Stephan,
G. Onishchukov,
B. Schmauss,
G. Leuchs
The performance of a nonlinear amplifying loop mirror as a 2R-regenerator for an 80-Gb/s return-to-zero differential-quadrature-phase-shift-keyed signal has been investigated. experimentally. A significant eye-opening improvement and a negative power penalty of up to 2.6 dB were obtained.
Quantum reconstruction of an intense polarization squeezed optical state
Ch. Marquardt,
J. Heersink,
R. Dong,
M. V. Chekhova,
A. B. Klimov,
L. L. Sanchez-Soto,
U. L. Andersen,
G. Leuchs
We perform a reconstruction of the polarization sector of the density matrix of an intense polarization squeezed beam starting from a complete set of Stokes measurements. By using an appropriate quasidistribution, we map this onto the Poincare space, providing a full quantum mechanical characterization of the measured polarization state.
High numerical aperture imaging with different polarization patterns
The modulation transfer function (MTF) is calculated for imaging with linearly, circularly and radially polarized light as well as for different numerical apertures and aperture shapes. Special detectors are only sensitive to one component of the electric energy density, e. g. the longitudinal component. For certain parameters this has advantages concerning the resolution when comparing to polarization insensitive detectors. It is also shown that in the latter case zeros of the MTF may appear which are purely due to polarization effects and which depend on the aperture angle. Finally some ideas are presented how to use these results for improving the resolution in lithography. (c) 2007 Optical Society of America
An efficient source of continuous variable polarization entanglement
Ruifang Dong,
Joel Heersink,
Jun-Ichi Yoshikawa,
Oliver Gloeckl,
Ulrik L. Andersen,
Gerd Leuchs
We have experimentally demonstrated the efficient creation of highly entangled bipartite continuous variable polarization states. Exploiting an optimized scheme for the production of squeezing using the Kerr non-linearity of a glass fibre we generated polarization squeezed pulses with a mean classical excitation in (S)over-cap(3). Polarization entanglement was generated by interfering two independent polarization squeezed fields on a symmetric beam splitter. The resultant beams exhibit strong quantum noise correlations in the dark (S)over-cap(1)-(S)over-cap(2) polarization plane. To verify entanglement generation, we characterized the quantum correlations of the system for two different sets of conjugate Stokes parameters. The quantum correlations along the squeezed and the anti-squeezed Stokes parameters were observed to be - 4.1 +/- 0.3 and - 2.6 +/- 0.3 dB below the shot noise level, respectively. The degree of correlations was found to depend critically on the beam-splitting ratio of the entangling beam splitter. Carrying out measurements on a different set of conjugate Stokes parameters, correlations of -3.6 +/- 0.3 and -3.4 +/- 0.3 dB have been observed. This result is more robust against asymmetries in the entangling beam splitter, even in the presence of excess noise.
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