58 research outputs found
Role of population transfer under strong probe conditions in electromagnetically induced transparency
We analyze theoretically the phenomenon of electromagnetically induced
transparency (EIT) under conditions where the probe laser is not in the usual
weak limit. We consider the effects in both three-level and four-level systems,
which are either closed or open (due to losses to an external metastable
level). We find that the EIT dip almost disappears in a closed three-level
system but survives in an open system. In four-level systems, there is a narrow
enhanced-absorption peak (EITA) at line center, which has applications as an
optical clock. The peak converts to an EIT dip in a closed system, but again
survives in an open system.Comment: 4 pages, 4 figure, accepted in Optics Communication
Velocity-selective resonance dips in the probe absorption spectra of Rb D2 transitions induced by a pump laser
We report experimental observation of velocity-selective resonances in the
Doppler-broadened probe absorption spectra of 85Rb and 87Rb D2 transitions in
the presence of a strong copropagating pump laser locked to a frequency within
the Doppler profile of the transition. The set of three dips having the
separation of allowed hyperfine transitions can be moved along the Doppler
profile by tuning the pump laser frequency indicating a resonance between the
pump laser frequency and the velocity shifted probe laser frequency.Comment: 7 pages, 4 figure
Laser induced breakdown of the magnetic field reversal symmetry in the propagation of unpolarized light
We show how a medium, under the influece of a coherent control field which is
resonant or close to resonance to an appropriate atomic transition, can lead to
very strong asymmetries in the propagation of unpolarized light when the
direction of the magnetic field is reversed. We show how EIT can be used to
mimic effects occuring in natural systems and that EIT can produce very large
asymmetries as we use electric dipole allowed transitions. Using density matrix
calculations we present results for the breakdown of the magnetic field
reversal symmetry for two different atomic configurations.Comment: RevTex, 6 pages, 10 figures, Two Column format, submitted to Phys.
Rev.
Coherent Control of Magneto-optical Rotation in Inhomogeneously Broadened Medium
We extend our earlier investigations [Opt. Commun. {\bf 179}, 97 (2000)] on
the enhancement of magneto-optical rotation (MOR) to include inhomogeneous
broadening. We introduce a control field that counter-propagates with respect
to the probe field. We derive analytical results for the susceptibilities
corresponding to the two circular polarization components of the probe field.
From the analytical results we identify and numerically demonstrate the
region of parameters where significantly large magneto-optical rotation (MOR)
can be obtained. From the numerical results we isolate the significance of the
magnetic field and the control field in enhancement of MOR. The control field
opens up many new regions of the frequencies of the probe where large
magneto-optical rotation occurs. We also report that a large enhancement of MOR
can be obtained by operating the probe and control field in two-photon
resonance condition.Comment: REVTex format, 14 pages including 6 figures, to be published in
Optics Communication
Hybrid Ytterbium-doped large-mode-area photonic crystal fiber amplifier for long wavelengths.
A large-mode-area Ytterbium-doped photonic crystal fiber amplifier with build-in gain shaping is presented. The fiber cladding consists of a hexagonal lattice of air holes, where three rows are replaced with circular high-index inclusions. Seven missing air holes define the large-mode-area core. Light confinement is achieved by combined index and bandgap guiding, which allows for single-mode operation and gain shaping through distributed spectral filtering of amplified spontaneous emission. The fiber properties are ideal for amplification in the long wavelength regime of the Ytterbium gain spectrum above 1100 nm, and red shifting of the maximum gain to 1130 nm is demonstrated
Automatic DGD and GVD compensation at 640 Gb/s based on scalar radio-frequency spectrum measurement
We demonstrate what we believe to be the first real-time impairment-cancellation system for groupvelocity dispersion (GVD) and differential group delay (DGD) for a 640 Gb/s single-channel signal. Simultaneous compensation of two independent parameters is demonstrated by feedback control of separate GVD and DGD compensators using an impairment monitor based on an integrated all-optical radio-frequency (RF) spectrum analyzer.We show that low-bandwidth measurement of only a single tone in the RF spectrum is sufficient for automatic compensation for multiple degrees of freedom using a multivariate optimization scheme
Cross-correlated imaging of single-mode photonic crystal rod fiber with distributed mode filtering
Enhancement of Magneto-Optic Effects via Large Atomic Coherence
We utilize the generation of large atomic coherence to enhance the resonant
nonlinear magneto-optic effect by several orders of magnitude, thereby
eliminating power broadening and improving the fundamental signal-to-noise
ratio. A proof-of-principle experiment is carried out in a dense vapor of Rb
atoms. Detailed numerical calculations are in good agreement with the
experimental results. Applications such as optical magnetometry or the search
for violations of parity and time reversal symmetry are feasible
Electromagnetically induced transparency with a standing-wave drive in the frequency up-conversion regime
We study electromagnetically induced transparency for a probe traveling-wave (TW) laser field in closed Doppler-broadened three-level systems driven by a standing-wave (SW) laser field of moderate intensity (its Rabi frequencies are smaller than the Doppler width of the driven transition). We show that probe windows of transparency occur for values of the probe to drive field frequency ratio R close to half-integer values. For optical transitions and typical values of Doppler broadening for atoms in a vapor cell, we show that for R>1 a SW drive field is appreciably more efficient than a TW drive in inducing probe transparency. As examples, we consider parameters for real cascade schemes in barium atoms with R≈1.5 and in beryllium atoms with R≈3.5 showing that probe transmission values well above 50% are possible for conditions in which it is almost negligible either without driving field or with only one of the TW components of the drive. We show that a strongly asymmetric drive having two TW components with unequal intensities is even more eficient than a symmetric SW drive in inducing probe transparency. The case of arbitrary probe intensity is also considered
Simultaneous optical performance monitoring of chromatic dispersion and PMD for 40 Gb/s data transmission
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