1,572 research outputs found
Cavity QED with high-Q whispering gallery modes
We report measurements of cavity-QED effects for the radiative coupling of atoms in a dilute vapor to the external evanescent field of a whispering-gallery mode (WGM) in a fused silica microsphere. The high Q (5 x 10^(7)), small mode volume (10^(-8) cm^(3)), and unusual symmetry of the microcavity evanescent field enable velocity-selective interactions between fields with photon number of order unity in the WGM and (N) over bar(T) similar to 1 atoms in the surrounding vapor
High-Q measurements of fused-silica microspheres in the near infrared
Measurements of the quality factor Q ~ 8 x 10^9 are reported for the whispering-gallery modes (WGM’s) of quartz microspheres for the wavelengths 670, 780, and 850 nm; these results correspond to finesse F ~ 2.2 x 10^6. The observed independence of Q from wavelength indicates that losses for the WGM’s are dominated by a mechanism other than bulk absorption in fused silica in the near infrared. Data obtained by atomic force microscopy combined with a simple model for surface scattering suggest that Q can be limited by residual surface inhomogeneities. Absorption by absorbed water can also explain why the material limit is not reached at longer wavelengths in the near infrared
Transient Regime of Kerr Frequency Comb Formation
Temporal growth of an optical Kerr frequency comb generated in a
microresonator is studied both experimentally and numerically. We find that the
comb emerges from vacuum fluctuations of the electromagnetic field on
timescales significantly exceeding the ringdown time of the resonator modes.
The frequency harmonics of the comb spread starting from the optically pumped
mode if the microresonator is characterized with anomalous group velocity
dispersion. The harmonics have different growth rates resulting from sequential
four-wave mixing process that explains intrinsic modelocking of the comb.Comment: 4 pages, 5 figure
Hard and Soft Excitation Regimes of Kerr Frequency Combs
We theoretically study the stability conditions and excitation regimes of
hyper-parametric oscillation and Kerr frequency comb generation in continuously
pumped nonlinear optical resonators possessing anomalous group velocity
dispersion. We show that both hard and soft excitation regimes are possible in
the resonators. Selection between the regimes is achieved via change in the
parameters of the pumping light.Comment: 4 pages, 7 figure
Miniature Optical Atomic Clock: Stabilization of a Kerr Comb Oscillator
Mechanical clocks consist of a pendulum and a clockwork that translates the
pendulum period to displayed time. The most advanced clocks utilize optical
transitions in atoms in place of the pendulum and an optical frequency comb
generated by a femtosecond laser as the clockwork. The comb must be stabilized
at two points along its frequency spectrum: one with a laser to lock a comb
line to a transition in the atom, and another through self referencing to
stabilize the frequency interval between the comb lines. This approach requires
advanced techniques, so optical atomic clocks are currently laboratory devices
in specialized labs. In this paper we leverage unique properties of Kerr comb
oscillators for realization of optical atomic clocks in miniature form factors.
In particular, we describe a clock based on D1 transition of 87Rb that fits in
the palm of the hand, and can be further miniaturized to chip scale.Comment: 4 pages, 4 figure
Admittance spectroscopy of charge traps of FET based on nanotubes
Investigation of electrical properties of FET based on polymer wrapped nanotubes, namely charge carrier transport and trap appear mechanisms. Model of carrier transport in the device was performed. Local traps states activation energies were obtained
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