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We consider a significant lowering of the threshold of stimulated Raman scattering in solid fused silica spherical microlenses
cavities that is caused by an increase in the integral overlap factor of whispering gallery modes. The structure of focal
regions of a microlens is shown to have the shape of honeycombs, forming a photonic crystal or a photonic nanojet. We show
that, at comparatively small numerical apertures NA = 0.7–0.8, which correspond to hemispherical microlenses, a spherical microlens cavity exhibits the possibility of focusing
laser radiation beyond the Abbe diffraction limit. This enables the possibility of wide practical applications of microspheres
as a focusing element the resolving power of which exceeds the Abbe diffraction limit in the near field. The whispering-gallery-mode
spherical microlens cavity makes it possible to perform laser generation with a duration of a coherent pulse in the subfemtosecond
range and to form a subwavelength focal region of the near field. This ensures the possibility of detecting single molecules
of a substance in the subwavelength range in the near field and can be used to increase the sensitivity of intracavity spectroscopy
methods and as microlasers for excitation of molecules in metal molecular nanoswitches and semiconductor heterostructures.
From an array of microlens cavities, metamaterials with a negative refractive index can be formed. 相似文献
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M. V. Jouravlev 《Technical Physics》2010,55(10):1497-1503
Threshold conditions for electrothermal automodulation instability in high-Q ferroelectric microwave cryogenic resonators operating in the two-mode regime are investigated. The dependence of the electrothermal
automodulation frequency on the numbers of interacting modes for different combinations of thermal modes and surface electromagnetic
whispering-gallery modes is presented. The threshold power exciting the electrothermal automodulation of the oscillation of
the partial mode electromagnetic amplitudes is compared with the threshold power of strictional parametric excitation of acoustic
oscillations in the resonator. It is shown that the electrothermal automodulation in the two-mode regime may take place at
an excitation power from 10 to 120 μW depending on the combination of interacting thermal and electromagnetic surface modes.
Calculated threshold powers are low, which makes it possible to apply the electrothermal automodulation for improving the
sensitivity of resonance bolometers and distributed microwave antennas with basic elements built around nonlinear microwave
resonators. In addition, the electrothermal automodulation could be applied in developing novel microwave metamaterials. Nonlinear
microwave whispering-gallery cryogenic resonators can be used as elements increasing the sensitivity of EPR spectroscopy methods. 相似文献
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We investigate theoretically electron transfer in a double dot in a situation where spin blockade is lifted by nuclear magnetic field: this has been recently achieved in experiment [F. Koppens, Science 309, 1346 (2005)]. We show that for a given realization of nuclear magnetic field spin blockade can be restored by tuning external magnetic field; this may be useful for quantum manipulation of the device. 相似文献
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In this paper, we present some new properties of the Mitra‐Wan forestry model written as a discrete‐time optimal control problem. For this problem, the set of stationary states is characterized. For the optimal long‐run management, we consider the following optimality criteria: average optimality, good control policies, bias optimality, and overtaking optimality. We establish relationships between these criteria and show that the value of average optimal policies is constant and equals the value in the optimal stationary state. 相似文献
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We propose to accelerate reversal of the ferromagnetic order parameter in spin valves by electronic noise. By solving the stochastic equations of motion we show that the current-induced magnetization switching time is drastically reduced by a modest level of externally generated current (voltage) noise. This also leads to a significantly lower power consumption for the switching process. 相似文献
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