36 research outputs found
Noiseless electro-optic processing of optical signals generated with squeezed light
We demonstrate an elegant way of handling optical signals which are generated using squeezed states of light without losing their improved signal to noise ratio. We do this by amplifying, without significant noise penalty, both signal and noise away from the quantum noise limit into the classical domain. This makes the information robust to losses. Our system achieves a signal transfer coefficient, T-s, close to unity. As a demonstration we amplify a small signal carried by 35% amplitude squeezed light and show that unlike the fragile squeezed input, the signal amplified output is robust to propagation losses. A signal transfer coefficient of T-s = 0.75 is achieved even in the presence of large introduced (86%) downstream losses. (C) 1998 Optical Society of America
Intensity-noise properties of injection-locked lasers
We present experimental results that illustrate how laser intensity noise near the quantum-noise limit is transferred in an injection-locked cw Nd:(yttrium aluminum garnet) nonplanar ring-oscillator laser. We show that these results are in extremely good agreement with our quantum-mechanical model describing the injection locking process [T. C. Ralph, C. C. Harb, and H.-A. Bachor, Phys. Rev. A]. Three regions in the intensity-noise spectrum are identified and we show that different minimum noise levels exist in these regions. Finally, we show that the injection-locked laser can generate and preserve nonclassical states
Shot Noise in Digital Holography
We discuss on noise in heterodyne holography in an off-axis configuration. We
show that, for a weak signal, the noise is dominated by the shot noise on the
reference beam. This noise corresponds to an equivalent noise on the signal
beam of one photoelectron per pixel, for the whole sequence of images used to
build the digital hologram
Experimental realization of sub-shot-noise quantum imaging
Properties of quantum states have disclosed new technologies, ranging from
quantum information to quantum metrology. Among them a recent research field is
quantum imaging, addressed to overcome limits of classical imaging by
exploiting spatial properties of quantum states of light . In particular
quantum correlations between twin beams represent a fundamental resource for
these studies. One of the most interesting proposed scheme exploits spatial
quantum correlations between parametric down conversion light beams for
realizing sub-shot-noise imaging of the weak absorbing objects, leading ideally
to a noise-free imaging. Here we present the first experimental realisation of
this scheme, showing its capability to reach a larger signal to noise ratio
(SNR) with respect to classical imaging methods. This work represents the
starting point of this quantum technology that can have relevant applications,
especially whenever there is a need of a low photon flux illumination (e.g. as
with certain biological samples)
NOISELESS AMPLIFICATION OF THE COHERENT AMPLITUDE OF BRIGHT SQUEEZED-LIGHT USING A STANDARD LASER-AMPLIFIER (VOL 119, PG 301, 1995)
We propose a new arrangement of a laser amplifier which enables the coherent amplitude of bright squeezed light to be amplified without destroying the noise suppression. In addition the signal to noise for a modulation of the input beam is maintained in the amplified output beam
Noiseless Amplification of the Coherent Amplitude of Bright Squeezed-Light Using a Standard Laser-Amplifier
We propose a new arrangement of a laser amplifier which enables the coherent amplitude of bright squeezed light to be amplified without destroying the noise suppression. In addition the signal to noise for a modulation of the input beam is maintained in the amplified output beam
Active versus passive squeezing by second-harmonic generation
The characteristics of squeezed light generated by both passive (occurring in a cavity external to a laser) and active (occurring within a laser cavity) second-harmonic generation (SHG) are investigated and contrasted. Squeezing of both the fundamental and the second harmonic is discussed, and the issue of doubly versus singly resonant behavior is addressed. We examine passive squeezing by explicitly modeling the intrinsically noisy output of the pump laser and coupling it to a passive, multiport, lossy SHG cavity. Low-frequency degradation of the squeezing caused by the laser pump noise is predicted and provides a probable explanation for previous discrepancies between theory and experiment. Active squeezing is quantitatively modeled by a three-level laser model that retains all laser dynamics. Previously disparate predictions are reconciled. For one parameter set two regimes of squeezing are predicted: 50% squeezing at frequencies lower than the laser relaxation oscillation, and near-perfect squeezing at frequencies above. A particular problem of active squeezing is highlighted: The fast dephasing of the laser coherence introduces considerable excess noise likely to mask squeezing in experimental situations. We conclude that, although passive SHG is a practical source of squeezing, active SHG is unlikely to be so in the foreseeable future. (C) 1996 Optical Society of Americ