674 research outputs found
Influence of relaxation on propagation, storage and retrieving of light pulses in electromagnetically induced transparency medium
By solving the self-consistent system of Maxwell and density matrix equations
to the first order with respect to nonadiabaticity, we obtain an analytical
solution for the probe pulse propagation. The conditions for efficient storage
of light are analyzed. The necessary conditions for optical propagation
distance has been obtained.Comment: 7 pages, 7 figure
Electromagnetically induced transparency in an inverted Y-type four-level system
The interaction of a weak probe laser with an inverted-Y type four-level
atomic system driven by two additional coherent fields is investigated
theoretically. Under the influence of the coherent coupling fields, the
steady-state linear susceptibility of the probe laser shows that the system can
have single or double electromagnetically induced transparency windows
depending on the amplitude and the detuning of the coupling lasers. The
corresponding index of refraction associated with the group velocity of the
probe laser can be controlled at both transparency windows by the coupling
fields. The propagation of the probe field can be switched from superluminal
near the resonance to subluminal on resonance within the single transparency
window when two coupling lasers are on resonance. This provides a potential
application in quantum information processing. We propose an atomic
system for experimental observation
Self-referenced characterization of space-time couplings in near single-cycle laser pulses
We report on the characterization of space-time couplings in high energy
sub-2-cycle 770nm laser pulses using a self-referencing single-shot method.
Using spatially-encoded arrangement filter-based spectral phase interferometry
for direct electric field reconstruction (SEA-F-SPIDER) we characterize
few-cycle pulses with a wave-front rotation of 2.8x?10^11 rev/sec (1.38 mrad
per half-cycle) and pulses with pulse front tilts ranging from to -0.33 fs/um
to -3.03 fs/um.Comment: 6 pages, 6 figure
Coherent Patterning of Matter Waves with Subwavelength Localization
We propose the Subwavelength Localization via Adiabatic Passage (SLAP)
technique to coherently achieve state-selective patterning of matter waves well
beyond the diffraction limit. The SLAP technique consists in coupling two
partially overlapping and spatially structured laser fields to three internal
levels of the matter wave yielding state-selective localization at those
positions where the adiabatic passage process does not occur. We show that by
means of this technique matter wave localization down to the single nanometer
scale can be achieved. We analyze in detail the potential implementation of the
SLAP technique for nano-lithography with an atomic beam of metastable Ne* and
for coherent patterning of a two-component 87Rb Bose-Einstein condensate.Comment: 6 pages, 5 figure
Phase-sensitive Manipulations of Squeezed Vacuum Field in an Optical Parametric Amplifier inside an Optical Cavity
Squeezed vacuum field can be amplified or deamplified when it is injected, as
the signal beam, into a phase-sensitive optical parametric amplifier (OPA)
inside an optical cavity. The spectral features of the reflected quantized
signal field are controlled by the relative phase between the injected squeezed
vacuum field and the pump field for the OPA. The experimental results
demonstrate coherent phenomena of OPA in the quantum regime, and show
phase-sensitive manipulations of quantum fluctuations for quantum information
processing.Comment: 4 pages, 3 figures, appear in Phys. Rev. Let
Scanning Acoustic Microscopy Investigation of Frequency-Dependent Reflectance of Acid-Etched Human Dentin Using Homotopic Measurements
Composite restorations in modern restorative dentistry rely on the bond formed in the adhesive-infiltrated acid-etched dentin. The physical characteristics of etched dentin are, therefore, of paramount interest. However, characterization of the acid-etched zone in its natural state is fraught with problems stemming from a variety of sources including its narrow size, the presence of water, heterogeneity, and spatial scale dependency. We have developed a novel homotopic (same location) measurement methodology utilizing scanning acoustic microscopy (SAM). Homotopic measurements with SAM overcome the problems encountered by other characterization/ imaging methods. These measurements provide us with acoustic reflectance at the same location of both the pre- and post-etched dentin in its natural state. We have applied this methodology for in vitro measurements on dentin samples. Fourier spectra from acid-etched dentin showed amplitude reduction and shifts of the central frequency that were location dependent. Through calibration, the acoustic reflectance of acid-etched dentin was found to have complex and non-monotonic frequency dependence. These data suggest that acid-etching of dentin results in a near-surface graded layer of varying thickness and property gradations. The measurement methodology described in this paper can be applied to systematically characterize mechanical properties of heterogeneous soft layers and interfaces in biological materials
Analogue to multiple electromagnetically induced transparency in all-optical drop-filter systems
We theoretically study a parallel optical configuration which includes N
periodically coupled whispering-gallery-mode resonators. The model shows an
obvious effect which has a direct analogy with the phenomenon of multiple
electromagnetically induced transparency in quantum systems. The numerical
simulations illuminate that the frequency transparency windows are sharp and
highly transparent. We also briefly discuss the experimental feasibility of the
current scheme in two practical systems, microrings and microdisks.Comment: 4 pages, 4 figure
ATP transients accompany spontaneous contractions in isolated guinea-pig detrusor smooth muscle
Oocytes progress beyond prophase in the presence of DNA damage.
In the female germline, DNA damage has the potential to induce infertility and even to lead to genetic abnormalities that may be propagated to the resulting embryo [1, 2]. The protracted arrest in meiotic prophase makes oocytes particularly susceptible to the accumulation of environmental insults, including DNA damage. Despite this significant potential to harm reproductive capacity, surprisingly little is known about the DNA damage response in oocytes. We show that double-strand breaks in meiotically competent G2/prophase-arrested mouse oocytes do not prevent entry into M phase, unless levels of damage are severe. This lack of an efficient DNA damage checkpoint is because oocytes fail to effectively activate the master regulator of the DNA damage response pathway, ATM (ataxia telangiectasia mutated) kinase. In addition, instead of inhibiting cyclin B-CDK1 through destruction of Cdc25A phosphatase, oocytes utilize an inhibitory phosphorylation of Cdc25B. We conclude that oocytes are the only nontransformed cells that fail to launch a robust G2 phase DNA damage checkpoint and that this renders them sensitive to genomic instability
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