115,907 research outputs found
The Electromagnetically Induced Transparency in Mechanical Effects of Light
We consider the dynamical behavior of a nanomechanical mirror in a
high-quality cavity under the action of a coupling laser and a probe laser. We
demonstrate the existence of the analog of electromagnetically induced
transparency (EIT) in the output field at the probe frequency. Our calculations
show explicitly the origin of EIT-like dips as well as the characteristic
changes in dispersion from anomalous to normal in the range where EIT dips
occur. Remarkably the pump-probe response for the opto mechanical system shares
all the features of the Lambda system as discovered by Harris and
collaborators.Comment: 4 pages, 5 figure
Electromagnetically Induced Transparency from Two Phonon Processes in Quadratically Coupled Membranes
We describe how electromagnetically induced transparency can arise in
quadratically coupled optomechanical systems. Due to quadratic coupling the
underlying optical process involves a two phonon process in optomechanical
system and this two phonon process makes the mean amplitude, which plays the
role of atomic coherence in traditional EIT, zero. We show how the fluctuation
in displacement can play a role similar to atomic coherence and can lead to
EIT-like effects in quadratically coupled optomechanical systems. We show how
such effects can be studied using the existing optomechanical systems.Comment: 5 pages,4 figure
Can reactive coupling beat motional quantum limit of nano waveguides coupled to microdisk resonator
Dissipation is generally thought to affect the quantum nature of the system
in an adverse manner, however we show that dissipatively coupled nano systems
can be prepared in states which beat the standard quantum limit of the
mechanical motion. We show that the reactive coupling between the waveguide and
the microdisk resonator can generate the squeezing of the waveguide by
injecting a quantum field and laser into the resonator through the waveguide.
The waveguide can show about 70--75% of maximal squeezing for temperature about
1--10 mK. The maximum squeezing can be achieved with incident pump power of
only 12 W for a temperature of about 1 mK. Even for temperatures of 20 mK,
achievable by dilution refrigerators, the maximum squeezing is about 60%.Comment: 6 pages,2 figure
Sum-of-squares of polynomials approach to nonlinear stability of fluid flows: an example of application
With the goal of providing the first example of application of a recently proposed method, thus demonstrating its ability to give results in principle, global stability of a version of the rotating Couette flow is examined. The flow depends on the Reynolds number and a parameter characterising the magnitude of the Coriolis force. By converting the original Navier-Stokes equations to a finite-dimensional uncertain dynamical system using a partial Galerkin expansion, high-degree polynomial Lyapunov functionals were found by sum-of-squares-of-polynomials optimization. It is demonstrated that the proposed method allows obtaining the exact global stability limit for this flow in a range of values of the parameter characterising the Coriolis force. Outside this range a lower bound for the global stability limit was obtained, which is still better than the energy stability limit. In the course of the study several results meaningful in the context of the method used were also obtained. Overall, the results obtained demonstrate the applicability of the recently proposed approach to global stability of the fluid flows. To the best of our knowledge, it is the first case in which global stability of a fluid flow has been proved by a generic method for the value of a Reynolds number greater than that which could be achieved with the energy stability approach
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