17,007 research outputs found
Quantum radiation by an Unruh-DeWitt detector in oscillatory motion
Quantum radiated power emitted by an Unruh-DeWitt (UD) detector in linear
oscillatory motion in (3+1)D Minkowski space, with the internal harmonic
oscillator minimally coupled to a massless scalar field, is obtained
non-perturbatively by numerical method. The signal of the Unruh-like effect
experienced by the detector is found to be pronounced in quantum radiation in
the highly non-equilibrium regime with high averaged acceleration and short
oscillatory cycle, and the signal would be greatly suppressed by quantum
interference when the averaged proper acceleration is sufficiently low. An
observer at a fixed angle would see periods of negative radiated power in each
cycle of motion, while the averaged radiated power over a cycle is always
positive as guaranteed by the quantum inequalities. Coherent high harmonic
generation and down conversion are identified in the detector's quantum
radiation. Due to the overwhelming largeness of the vacuum correlators of the
free field, the asymptotic reduced state of the harmonics of the radiation
field is approximately a direct product of the squeezed thermal states.Comment: 30 pages, 10 figures, partly based on [arXiv:1601.07006
Radiation pattern of a classical dipole in a photonic crystal: photon focusing
The asymptotic analysis of the radiation pattern of a classical dipole in a
photonic crystal possessing an incomplete photonic bandgap is presented. The
far-field radiation pattern demonstrates a strong modification with respect to
the dipole radiation pattern in vacuum. Radiated power is suppressed in the
direction of the spatial stopband and strongly enhanced in the direction of the
group velocity, which is stationary with respect to a small variation of the
wave vector. An effect of radiated power enhancement is explained in terms of
\emph{photon focusing}. Numerical example is given for a square-lattice
two-dimensional photonic crystal. Predictions of asymptotic analysis are
substantiated with finite-difference time-domain calculations, revealing a
reasonable agreement.Comment: Submitted to Phys. Rev.
A 10-Watt X-Band Grid Oscillator
A 100-transistor MESFET grid oscillator has been fabricated that generates an effective radiated power of 660 W at 9.8 GHz and has a directivity of 18.0 dB. This corresponds to a total radiated power of 10.3 W, or 103 mW per device. This is the largest recorded output power for a grid oscillator. The grid drain-source bias voltage is 7.4 V and the total drain current for the grid is 6.0 A, resulting in an overall dc-to-rf efficiency of 23%. The pattern of the SSB noise-to-carrier ratio was measured and found to be essentially independent of the radiation angle. The average SSB noise level was -87 dBc/Hz at an offset of 150 kHz from the carrier. An average improvement in the SSB noise-to-carrier ratio of 5 dB was measured for a 100-transistor grid compared to a 16-transistor gri
Quantum Cloning for Absolute Radiometry
In the quantum regime information can be copied with only a finite fidelity.
This fidelity gradually increases to 1 as the system becomes classical. In this
article we show how this fact can be used to directly measure the amount of
radiated power. We demonstrate how these principles could be used to build a
practical primary standard
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