509 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
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
The DNA damage response in mammalian oocytes
DNA damage is one of the most common insults that challenge all cells. To cope, an elaborate molecular and cellular response has evolved to sense, respond to and correct the damage. This allows the maintenance of DNA fidelity essential for normal cell viability and the prevention of genomic instability that can lead to tumor formation. In the context of oocytes, the impact of DNA damage is not one of tumor formation but of the maintenance of fertility. Mammalian oocytes are particularly vulnerable to DNA damage because physiologically they may lie dormant in the ovary for many years (>40 in humans) until they receive the stimulus to grow and acquire the competence to become fertilized. The implication of this is that in some organisms, such as humans, oocytes face the danger of cumulative genetic damage for decades. Thus, the ability to detect and repair DNA damage is essential to maintain the supply of oocytes necessary for reproduction. Therefore, failure to confront DNA damage in oocytes could cause serious anomalies in the embryo that may be propagated in the form of mutations to the next generation allowing the appearance of hereditary disease. Despite the potential impact of DNA damage on reproductive capacity and genetic fidelity of embryos, the mechanisms available to the oocyte for monitoring and repairing such insults have remained largely unexplored until recently. Here, we review the different aspects of the response to DNA damage in mammalian oocytes. Specifically, we address the oocyte DNA damage response from embryonic life to adulthood and throughout oocyte development
Three level atom optics via the tunneling interaction
Three level atom optics (TLAO) is introduced as a simple, efficient and
robust method to coherently manipulate and transport neutral atoms. The
tunneling interaction among three trapped states allows to realize the spatial
analog of the stimulated Raman adiabatic passage (STIRAP), coherent population
trapping (CPT), and electromagnetically induced transparency (EIT) techniques.
We investigate a particular implementation in optical microtrap arrays and show
that under realistic parameters the coherent manipulation and transfer of
neutral atoms among dipole traps could be realized in the millisecond range.Comment: 5 pages, 6 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
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
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
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