333 research outputs found
Coherent population trapping in ruby crystal at room temperature
Observation of coherent population trapping (CPT) at ground-state Zeeman
sublevels of -ion in ruby is reported. The experiments are performed
at room temperature by using both nanosecond optical pulses and nanosecond
trains of ultrashort pulses. In both cases sharp drops in the resonantly
induced fluorescence are detected as the external magnetic field is varied.
Theoretical analysis of CPT in a transient regime due to pulsed action of
optical pulses is presented.Comment: 4 pages, 4 figures, submitted to PR
Generation of coherent terahertz pulses in Ruby at room temperature
We have shown that a coherently driven solid state medium can potentially
produce strong controllable short pulses of THz radiation. The high efficiency
of the technique is based on excitation of maximal THz coherence by applying
resonant optical pulses to the medium. The excited coherence in the medium is
connected to macroscopic polarization coupled to THz radiation. We have
performed detailed simulations by solving the coupled density matrix and
Maxwell equations. By using a simple -type energy scheme for ruby, we have
demonstrated that the energy of generated THz pulses ranges from hundreds of
pico-Joules to nano-Joules at room temperature and micro-Joules at liquid
helium temperature, with pulse durations from picoseconds to tens of
nanoseconds. We have also suggested a coherent ruby source that lases on two
optical wavelengths and simultaneously generates THz radiation. We discussed
also possibilities of extension of the technique to different solid-state
materials
Effective unidirectional pumping for steady-state amplification without inversion
We discuss an opportunity to achieve amplification without inversion in
three-level cascade scheme using an effective unidirectional pumping via
bidirectional incoherent pump. Analytical solution to the population and the
coherence are obtained in the steady-state regime. With a proper choice of the
parameters, obtained here, the possibility for amplification without inversion
is presented.Comment: 8 Pages, 7 figure
Infrared generation in low-dimensional semiconductor heterostructures via quantum coherence
A new scheme for infrared generation without population inversion between
subbands in quantum-well and quantum-dot lasers is presented and documented by
detailed calculations. The scheme is based on the simultaneous generation at
three frequencies: optical lasing at the two interband transitions which take
place simultaneously, in the same active region, and serve as the coherent
drive for the IR field. This mechanism for frequency down-conversion does not
rely upon any ad hoc assumptions of long-lived coherences in the semiconductor
active medium. And it should work efficiently at room temperature with
injection current pumping. For optimized waveguide and cavity parameters, the
intrinsic efficiency of the down-conversion process can reach the limiting
quantum value corresponding to one infrared photon per one optical photon. Due
to the parametric nature of IR generation, the proposed inversionless scheme is
especially promising for long-wavelength (far- infrared) operation.Comment: 4 pages, 1 Postscript figure, Revtex style. Replacement corrects a
printing error in the authors fiel
Superradiance in media with a near-zero refractive index
The dependence of the efficiency of collective spontaneous emission in a spherical medium on the modulus of a complex refractive index approaching zero and on the ordering of optical centers is studied. © Allerton Press, Inc., 2012
Ultraslow light in inhomogeneously broadened media
We calculate the characteristics of ultraslow light in an inhomogeneously
broadened medium. We present analytical and numerical results for the group
delay as a function of power of the propagating pulse. We apply these results
to explain the recently reported saturation behavior [Baldit {\it et al.}, \prl
{\bf 95}, 143601 (2005)] of ultraslow light in rare earth ion doped crystal.Comment: 4 pages, 5 figure
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