241,468 research outputs found
Grating induced transparency (GIT) and the dark mode in optical waveguides
We propose and describe a new class of optical modes consisting of superposition of three waveguide modes which can be supported by a few-mode waveguide spatially modulated by two co-spatial gratings. These supermodes bear a close, but not exact, formal analogy to the three-level quantum states involved in EIT and its attendant slow light propagation characteristics. Of particular interest is the supermode which we call the dark mode in which, in analogy with the dark state of EIT, one of the three uncoupled waveguide modes is not excited. This mode has unique dispersion characteristics that translate into a slow light propagation which possesses high bandwidth-delay product and can form the basis for a new generation of optical resonators and lasers
Modal Spectroscopy of Optoexcited Vibrations of a Micron-Scale On-Chip Resonator at Greater than 1 GHz Frequency
We analyze experimentally and theoretically >1 GHz optoexcited mechanical vibration in an on-chip micron-scaled sphere. Different eigen-mechanical modes are excited upon demand by the centrifugal radiation pressure of the optical whispering-gallery-mode, enabling an optomechanical modal spectroscopy investigation of many vibrational modes. Spectral analysis of the light emitted from the device enables deduction of its natural vibrational modes in analogy with spectroscopy of a molecule's vibrational levels, and its eccentricity perturbation is shown to induce spectral splitting
Basis-dependent dynamics of trapped Bose-Einstein condensates and analogies with semi-classical laser theory
We present a consistent second order perturbation theory for the lowest-lying
condensed modes of very small, weakly-interacting Bose-Einstein condensates in
terms of bare particle eigenstates in a harmonic trap. After presenting our
general approach, we focus on explicit expressions for a simple three-level
system, mainly in order to discuss the analogy of a single condensate occupying
two modes of a trap with the semi-classical theory for two-mode photon lasers.
A subsequent renormalization of the single-particle energies to include the
dressing imposed by mean fields demonstrates clearly the consistency of our
treatment with other kinetic approaches.Comment: 2 Modified Sections: (i) Analogy between 2-mode BEC and
Semi-classical laser theory (ii) Links to other kinetic theories made more
explicit. European Physical Journal D (accepted for publication): Laser
Cooling and Quantum Gas Sectio
Leaky modes of waveguides as a classical optics analogy of quantum resonances
A classical optics waveguide structure is proposed to simulate resonances of
short range one-dimensional potentials in quantum mechanics. The analogy is
based on the well known resemblance between the guided and radiation modes of a
waveguide with the bound and scattering states of a quantum well. As resonances
are scattering states that spend some time in the zone of influence of the
scatterer, we associate them with the leaky modes of a waveguide, the latter
characterized by suffering attenuation in the direction of propagation but
increasing exponentially in the transverse directions. The resemblance is
complete since resonances (leaky modes) can be interpreted as bound states
(guided modes) with definite lifetime (longitudinal shift). As an immediate
application we calculate the leaky modes (resonances) associated with a
dielectric homogeneous slab (square well potential) and show that these modes
are attenuated as they propagate.Comment: The title has been modified to describe better the contents of the
article. Some paragraphs have been added to clarify the result
Classical Fields Near Thermal Equilibrium
We discuss the classical limit for the long-distance (``soft'') modes of a
quantum field when the hard modes of the field are in thermal equilibrium. We
address the question of the correct semiclassical dynamics when a momentum
cut-off is introduced. Higher order contributions leads to a stochastic
interpretation for the effective action in analogy to Quantum Brownian Motion,
resulting in dissipation and decoherence for the evolution of the soft modes.
Particular emphasis is put on the understanding of dissipation. Our discussion
focuses mostly on scalar fields, but we make some remarks on the extension to
gauge theories.Comment: REVTeX, 6 figure
Loss analysis of air-core photonic crystal fibers
By using a multipole moment approach, we analyze the loss of an air-core photonic crystal fiber and demonstrate that it is possible reduce the transmission loss that is due to photon radiation leakage through the photonic crystal cladding to a level below 0.01 dB/km, with eight rings of air holes. An analogy is drawn between air-core photonic crystal fiber modes and Bragg fiber modes. The influence of material absorption in the silica glass is discussed
Geometric phases in astigmatic optical modes of arbitrary order
The transverse spatial structure of a paraxial beam of light is fully
characterized by a set of parameters that vary only slowly under free
propagation. They specify bosonic ladder operators that connect modes of
different order, in analogy to the ladder operators connecting
harmonic-oscillator wave functions. The parameter spaces underlying sets of
higher-order modes are isomorphic to the parameter space of the ladder
operators. We study the geometry of this space and the geometric phase that
arises from it. This phase constitutes the ultimate generalization of the Gouy
phase in paraxial wave optics. It reduces to the ordinary Gouy phase and the
geometric phase of non-astigmatic optical modes with orbital angular momentum
states in limiting cases. We briefly discuss the well-known analogy between
geometric phases and the Aharonov-Bohm effect, which provides some
complementary insights in the geometric nature and origin of the generalized
Gouy phase shift. Our method also applies to the quantum-mechanical description
of wave packets. It allows for obtaining complete sets of normalized solutions
of the Schr\"odinger equation. Cyclic transformations of such wave packets give
rise to a phase shift, which has a geometric interpretation in terms of the
other degrees of freedom involved.Comment: final versio
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