390 research outputs found
Fresnel filtering of Gaussian beams in microcavities
We study the output from the modes described by the superposition of Gaussian
beams confined in the quasi-stadium microcavities. We experimentally observe
the deviation from Snell's law in the output when the incident angle of the
Gaussian beam at the cavity interface is near the critical angle for total
internal reflection, providing direct experimental evidence on the Fresnel
filtering. The theory of the Fresnel filtering for a planar interface
qualitatively reproduces experimental data, and a discussion is given on small
deviation between the measured data and the theory.Comment: 3 pages, 2 figure
Gain-tunable optomechanical cooling in a laser cavity
We study the optical cooling of the resonator mirror in a
cavity-optomechanical system that contains an optical gain medium. We find that
the optical damping rate is vanishingly small for an incoherently pumped laser
above threshold. In the presence of an external coherent drive however, the
optical damping rate can be enhanced substantially with respect to that of a
passive cavity. We show that the strength of the incoherent pump provides a
conduit to tune the damping rate and the minimum attainable phonon number with
the same radiation pressure force, and the latter can be lowered from that of a
passive cavity if the thermal contribution is nonnegligible. We also show that
the system can undergo a transition from the weak optomechanical coupling
regime to the strong optomechanical coupling regime as the incoherent pump
strength is varied.Comment: 7 pages, 5 figure
The quantum optical Josephson interferometer
The interplay between coherent tunnel coupling and on-site interactions in
dissipation-free bosonic systems has lead to many spectacular observations,
ranging from the demonstration of number-phase uncertainty relation to quantum
phase transitions. To explore the effect of dissipation and coherent drive on
tunnel coupled interacting bosonic systems, we propose a device that is the
quantum optical analog of a Josephson interferometer. It consists of two
coherently driven linear optical cavities connected via a central cavity with a
single-photon nonlinearity. The Josephson-like oscillations in the light
emitted from the central cavity as a function of the phase difference between
two pumping fields can be suppressed by increasing the strength of the
nonlinear coupling. Remarkably, we find that in the limit of ultra-strong
interactions in the center-cavity, the coupled system maps on to an effective
Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling
strength. In the limit of a single nonlinear cavity coupled to two linear
waveguides, the degree of photon antibunching from the nonlinear cavity
provides an excellent measure of the transition to the nonlinear regime where
Josephson oscillations are suppressed.Comment: 9 pages, 7 figure
The quantum optical Josephson interferometer
The interplay between coherent tunnel coupling and on-site interactions in
dissipation-free bosonic systems has lead to many spectacular observations,
ranging from the demonstration of number-phase uncertainty relation to quantum
phase transitions. To explore the effect of dissipation and coherent drive on
tunnel coupled interacting bosonic systems, we propose a device that is the
quantum optical analog of a Josephson interferometer. It consists of two
coherently driven linear optical cavities connected via a central cavity with a
single-photon nonlinearity. The Josephson-like oscillations in the light
emitted from the central cavity as a function of the phase difference between
two pumping fields can be suppressed by increasing the strength of the
nonlinear coupling. Remarkably, we find that in the limit of ultra-strong
interactions in the center-cavity, the coupled system maps on to an effective
Jaynes-Cummings system with a nonlinearity determined by the tunnel coupling
strength. In the limit of a single nonlinear cavity coupled to two linear
waveguides, the degree of photon antibunching from the nonlinear cavity
provides an excellent measure of the transition to the nonlinear regime where
Josephson oscillations are suppressed.Comment: 9 pages, 7 figure
Strong Electron-Hole Exchange in Coherently Coupled Quantum Dots
We have investigated few-body states in vertically stacked quantum dots. Due
to small inter-dot tunneling rate, the coupling in our system is in a
previously unexplored regime where electron-hole exchange is the dominant spin
interaction. By tuning the gate bias, we are able to turn this coupling off and
study a complementary regime where total electron spin is a good quantum
number. The use of differential transmission allows us to obtain unambiguous
signatures of the interplay between electron and hole spin interactions. Small
tunnel coupling also enables us to demonstrate all-optical charge sensing,
where conditional exciton energy shift in one dot identifies the charging state
of the coupled partner.Comment: 10 pages, 3 figure
Signatures of the super fluid-insulator phase transition in laser driven dissipative nonlinear cavity arrays
We analyze the non-equilibrium dynamics of a gas of interacting photons in an
array of coupled dissipative nonlinear cavities driven by a pulsed external
coherent field. Using a mean-field approach, we show that the system exhibits a
phase transition from a Mott-insulator-like to a superfluid regime. For a given
single-photon nonlinearity, the critical value of the photon tunneling rate at
which the phase transition occurs increases with the increasing photon loss
rate. We checked the robustness of the transition by showing its insensitivity
to the initial state prepared by the the pulsed excitation. We find that the
second-order coherence of cavity emission can be used to determine the phase
diagram of an optical many-body system without the need for thermalization.Comment: 4 pages, 4 figure
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