18 research outputs found
Broadband optical gain via interference in the free electron laser: principles and proposed realizations
We propose experimentally simplified schemes of an optically dispersive
interface region between two coupled free electron lasers (FELs), aimed at
achieving a much broader gain bandwidth than in a conventional FEL or a
conventional optical klystron composed of two separated FELs. The proposed
schemes can {\it universally} enhance the gain of FELs, regardless of their
design when operated in the short pulsed regime
Coherent control of ac Stark allowed transition in system
We show that quantum-interference-related phenomena, such as
electromagnetically induced transparency, gain without inversion and enhanced
refractive index may occur on electric-dipole forbidden transitions.
Gain/dispersion characteristics of such transitions strongly depend upon the
relative phase between the driving and probe fields. Unlike allowed
transitions, gain/absorption behavior of forbidden transitions exhibit
antisymmetric feature on the Rabi sidebands. Absorption/gain spectra possess
extremely narrow sub-natural resonances.Comment: 5 pages, 5 figure
Quantum Coherence in a Single Ion due to strong Excitation of a metastable Transition
We consider pump-probe spectroscopy of a single ion with a highly metastable
(probe) clock transition which is monitored by using the quantum jump
technique. For a weak clock laser we obtain the well known Autler-Townes
splitting. For stronger powers of the clock laser we demonstrate the transition
to a new regime. The two regimes are distinguished by the transition of two
complex eigenvalues to purely imaginary ones which can be very different in
magnitude. The transition is controlled by the power of the clock laser. For
pump on resonance we present simple analytical expressions for various
linewidths and line positions.Comment: 6 figures. accepted for publication in PR
Gain without population inversion in V-type systems driven by a frequency-modulated field
We obtain gain of the probe field at multiple frequencies in a closed
three-level V-type system using frequency modulated pump field. There is no
associated population inversion among the atomic states of the probe
transition. We describe both the steady-state and transient dynamics of this
system. Under suitable conditions, the system exhibits large gain
simultaneously at series of frequencies far removed from resonance. Moreover,
the system can be tailored to exhibit multiple frequency regimes where the
probe experiences anomalous dispersion accompanied by negligible
gain-absorption over a large bandwidth, a desirable feature for obtaining
superluminal propagation of pulses with negligible distortion.Comment: 10 pages + 8 figures; To appear in Physical Review
Observation of absorptive photon switching by quantum interference
We report an experimental demonstration of photon switching by quantum
interference in a four-level atomic system proposed by Harris and Yamamoto
(Phys. Rev. Lett. 81, 3611 (1998)). Quantum interference inhibits single-photon
absorption but enhances third-order, two-photon type absorption in the
four-level system. We have observed greatly enhanced nonlinear absorption in
the four-level system realized with cold 87Rb atoms and demonstrated fast
switching of the nonlinear absorption with a pulsed pump laser.Comment: 12 pages, 4 figure
Lasing without inversion in three-level systems without external coherent driving
We have studied an incoherently pumped laser operating with a Doppler-broadened three-level system placed in a doubly resonant cavity. This system generates two laser fields, one of them without population inversion. Both ladder and V-type three-level schemes are considered with a ratio R=ωα/ωβ of inversionless laser frequency ωα to ordinary laser frequency ωβ of R=0.67 and R=1.88, respectively. Dual-wavelength lasing extends up to Doppler-broadening values for optical transitions of atoms in a vapor cell. Some considerations for the practical realization of this dual-wavelength laser are discussed