We consider mid-infrared (5 - 25 μm), optically cooled detectors based on a microcantilever sensor of the radiation
pressure. The significant enhancement of sensitivity is due the combination of low effective temperature (10 K), non-absorption
detection and a high quality optical microcavity. Spectrometry applications are analyzed. It is shown that an
optically cooled radiation pressure sensor potentially has an order of magnitude better sensitivity than the best
conventional uncooled detectors.
We numerically examine the spatial evolution of the structure of coherent and partially coherent laser beams (PCBs),
including the optical vortices, propagating in turbulent atmospheres. The influence of beam fragmentation and
wandering relative to the axis of propagation (z-axis) on the value of the scintillation index (SI) of the signal at the
detector is analyzed. A method for significantly reducing the SI, by averaging the signal at the detector over a set of
PCBs, is described. This novel method is to generate the PCBs by combining two laser beams - Gaussian and vortex
beams, with different frequencies (the difference between these two frequencies being significantly smaller than the
frequencies themselves). In this case, the SI is effectively suppressed without any high-frequency modulators.
We consider theoretically and numerically the suppression of fluctuations (scintillations) of a laser
beam propagating through turbulent atmospheres by applying a phase modulator. Both spatial and
temporal phase variations introduced by this phase modulator are analyzed. The explicit
dependences of the scintillation index on the initial correlation length and finite-time phase
variations for long propagation paths are obtained. Results of modeling and numerical simulations
are presented. We demonstrate that an appropriately chosen phase modulator can significantly
suppress the scintillations of the laser beam caused by turbulent atmospheres.
Recently we proposed a new approach which potentially has single spin sensitivity, sub-nanometer
spatial resolution, and ability to operate at room temperature (J. Appl. Phys. 97, 014903 (2005);
U.S. Patent No. 7,305,869, 2007). In our approach a nanoscale photoluminescent center exhibits
optically detected magnetic resonance (ODMR) in the vicinity of magnetic moment in the sample
related with unpaired individual electron or nuclear spins, or ensemble of spins. We consider as a
sensor material that exhibit ODMR properties nitrogen-vacancy (N-V) centers in diamond. N-V
centers in diamond has serious advantage having extraordinary chemical and photostability, very
long spin lifetimes, and ability single-spin detection at room temperature. The variety of possible
scanning schemes has been considered. The potential application to 3D imaging of biological
structure has been analyzed.
A new concept of a free-space, high-speed optical communication (FSOC) system based on spectral encoding of radiation
from a broadband pulsed laser is developed. It is known that the intensity fluctuations of a partially coherent beam in
combination with a time-averaging photodetector leads to a significant scintillation reduction with the corresponding
improvement of the bit error rate by several orders of magnitude. Unfortunately, the time-averaging method cannot be
applied directly to gigabit data rate communication. The main limitation of this method is related to the requirement that the
correlation time between different spatially coherent spots be shorter than the response time of the photodetector. We
propose to extend the technique of scintillation suppression, based on time averaging of a partially coherent beam, to gigabit
data rate FSOC. In our approach, information is encoded in the form of amplitude modulation of the spectral components of
the laser pulse which has a broad spectrum. To examine the intensity fluctuations of a partially coherent beam under the
conditions of strong turbulence, we developed an asymptotic method for solution of the kinetic equation for the photon
distribution function. We show that, for long distances, scintillations and beam wandering can be significantly suppressed.
We consider midinfrared (5 - 25 μm) and terahertz (100 - 1000 μm), room-temperature detectors based on a
microcantilever/micromirror sensor of the radiation pressure. The significant enhancement of sensitivity is due the
combination of non-absorption detection and a high quality optical microcavity. Applications for spectrometry and imaging
are analyzed. It is shown that the radiation pressure sensor potentially has sensitivity at the level of or better than the best
conventional uncooled detectors.
The photon density operator function is used to describe the propagation of single-photon pulses through a
turbulent atmosphere. The effects of statistical properties of photon source and the effects of a random phase
screen on the variance of photon counting are studied. A procedure for reducing the total noise is discussed.
The physical mechanisms responsible for this reduction are explained.
The role of interference and entanglement in quantum neural processing is discussed. It is argued that on contrast to the quantum computing the problem of the use of exponential resources as the payment for the absence of entanglement does not exist for quantum neural processing. This is because of corresponding systems, as any modern classical artificial neural system, do not realize functions precisely, but approximate them by training on small sets of examples. It can permit to implement quantum neural systems optically, because in this case there is no need in exponential resources of optical devices (beam-splitters etc.). On the other hand, the role of entanglement in quantum neural processing is still very important, because it actually associates qubit states: this is necessary feature of quantum neural memory models.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.