We experimentally investigate the amplitude and phase transfer characteristics of a modified nonlinear optical loop mirror (NOLM) with a directional attenuator (DA-NOLM) optimized for differential phase-shift keying signal regeneration. The results show that the phase relation is preserved in the setup and thus the DA-NOLM is suitable for amplitude regeneration of phase-shift-keyed signals.
Nonunity gain quantum nondemolition measurements based on measurement
and repreparation
Jessica Schneider,
Oliver Gloeckl,
Gerd Leuchs,
Ulrik L. Andersen
We demonstrate experimentally a nonunity gain quantum nondemolition measurement based on a simple homodyne measurement and recreation strategy. Although the output state is an amplified version of the input state, the device meets standard criteria for QND measurements: the transfer coefficient was measured to 1,78, and the conditional variance was measured to 0.66. (c) 2006 Optical Society of America.
Distillation of squeezing from non-Gaussian quantum states
J. Heersink,
Ch. Marquardt,
R. Dong,
R. Filip,
S. Lorenz,
G. Leuchs,
U. L. Andersen
We show that single copy distillation of squeezing from continuous variable non-Gaussian states is possible using linear optics and conditional homodyne detection. A specific non-Gaussian noise source, corresponding to a random linear displacement, is investigated experimentally. Conditioning the signal on a tap measurement, we observe probabilistic recovery of squeezing.
Reduction of guided acoustic wave Brillouin scattering in photonic
crystal fibers
D. Elser,
U. L. Andersen,
A. Korn,
O. Gloeckl,
S. Lorenz,
Ch. Marquardt,
G. Leuchs
Guided acoustic wave Brillouin scattering (GAWBS) generates phase and polarization noise of light propagating in glass fibers. This excess noise affects the performance of various experiments operating at the quantum noise limit. We experimentally demonstrate the reduction of GAWBS noise in a photonic crystal fiber in a broad frequency range by tailoring the acoustic modes using the photonic also as a phononic crystal. We compare the noise spectrum to the one of a standard fiber and observe a tenfold noise reduction in the frequency range up to 200 MHz. Based on our measurement results as well as on numerical simulations, we establish a model for the reduction of GAWBS noise in photonic crystal fibers.
Using a quantum well heterostructure to study the longitudinal and
transverse electric field components of a strongly focused laser beam
G. Kihara Rurimo,
M. Schardt,
S. Quabis,
S. Malzer,
Ch. Dotzler,
A. Winkler,
G. Leuchs,
G. H. Dohler,
D. Driscoll, et al.
JOURNAL OF APPLIED PHYSICS
100
(2)
023112
(2006)
| Journal
We report a method to measure the electric energy density of longitudinal and transverse electric field components of strongly focused polarized laser beams. We used a quantum well photodetector and exploited the polarization dependent optical transitions of light holes and heavy holes to probe the electric field distribution in the focal region. A comparison of the measured photocurrent spectra for radially and azimuthally polarized beams at the light and heavy hole absorption peaks provides a measure of the amount of the longitudinal electric field component. (c) 2006 American Institute of Physics.
Verifying continuous-variable entanglement of intense light pulses
Three different methods have been discussed to verify continuous variable entanglement of intense light beams. We demonstrate all three methods using the same setup to facilitate the comparison. The nonlinearity used to generate entanglement is the Kerr effect in optical fibers. Due to the brightness of the entangled pulses, standard homodyne detection is not an appropriate tool for the verification. However, we show that by using large asymmetric interferometers on each beam individually, two noncommuting variables can be accessed and the presence of entanglement verified via joint measurements on the two beams. Alternatively, we witness entanglement by combining the two beams on a beam splitter that yields certain linear combinations of quadrature amplitudes which suffice to prove the presence of entanglement.
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