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An opportunity to exploit specific mechanisms of the acousto-optic nonlinearity to regulate performances of the collinear acousto-optical filter, realizing the sequential spectrum analysis of optical signals, is considered. This possibility is theoretically analyzed and experimentally confirmed with an advanced filter based on calcium molybdate (CaMoO4) single-crystal with a 15-μs time-aperture. It is able to operate over red and near-infrared light at relatively low radio-wave frequencies providing almost lossless regime for controlling acoustic waves of the finite amplitude. Under certain conditions, the transmission function of electronically tunable filter exhibits a marked dependence on the applied acoustic power density, and as a result, one can significantly squeeze the transmission function, i.e., improve the spectral resolution of this filter at the cost of decreasing the efficiency of the device partially. The identified and observed non-linear effect makes possible varying the performance data of similar advanced collinear acousto-optical filter governed by external signals of the finite amplitude. © 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.OE.52.6.064001]
Collinear acousto-optical interaction Optical filter Acousto-optical nonlinearity Transmission function Spectral resolution Waves of the finite amplitude CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA
New physical aspects of collinear acousto-optical interaction, occurred by acoustic waves of finite amplitude, are revealed and analyzed in crystalline materials exhibiting moderate linear acoustic losses. The analysis is performed in the regime of continuous traveling waves allowing a specific mechanism of the acousto-optic nonlinearity. Our consideration has shown that such nonlinearity together with linear acoustic losses is able to affect the transmission function inherent in collinear interaction. In particular, the mere presence of linear acoustic losses by themselves leads to broadening the width of the transmission function beginning already from very low levels of the applied acoustic power. Moreover, the transmission function exhibits a marked and quasi-periodical dependence on the applied acoustic power density, and that periodicity is governed by the linear acoustic losses. As a result, the transmission function can be significantly narrowed near isolated points at the cost of decreasing the interaction efficiency. These novelties related to collinear acousto-optical interaction accompanied by moderate linear acoustic losses have been studied and confirmed experimentally with an advanced acousto-optical cell based on calcium molybdate (CaMoO4) single crystal and controlled by acoustic waves of finite amplitude. © 2013 Optical Society of America
An advanced conceptual design of a high-bit-rate triple product acousto-optical processor is presented that can be applied in a number of astrophysical problems. We briefly describe the Large Millimeter Telescope as one of the potential observational infrastructures where the acousto-optical spectrometer can be successfully used. A summary on the study of molecular gas in relatively old (age > 10 Myr) disks around main sequence stars is provided. We have identified this as one of the science cases in which the proposed processor can have a big impact. Then we put forward triple product acousto-optical processor is able to realize algorithm of the space-and-time integrating, which is desirable for a wideband spectrum analysis of radio-wave signals with an improved resolution providing the resolution power of about 105 - 106 . It includes 1D-acousto-optic cells as the input devices for a 2D-optical data processing. The importance of this algorithm is based on exploiting the chirp Z-transform technique providing a 2D-Fourier transform of the input signals. The system produces the folded spectrum, accumulating advantages of both space and time integrating. Its frequency bandwidth is practically equal to the bandwidth of transducers inherent in acousto-optical cells. Then, similar processor is able to provide really high frequency resolution, which is practically equal to the reciprocal of the CCD-matrix photo-detector integration time. Here, the current state of developing the triple product acousto-optical processor in frames of the astrophysical instrumentation is shortly discussed.
Astrophysical Instrumentation Radio-Astronomy Millimeter-Wave Spectrometer Space-and-Time Integrating Acousto-Optical Devices Optical Processing System CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA FÍSICA ÓPTICA ÓPTICA
In this work the electrical characterization of n-channel a-SiGe:H TFTs with planarized gate electrode is presented. The planarized a-SiGe:H TFTs were fabricated at 200°C on corning glass substrate. The devices exhibit a subthreshold slope of 0.56 V/Decade, an on/off-current ratio approximately of 10⁶ and off-current approximately of 0.3x10⁻¹² A. The results show an improvement of the electrical characteristics when are compared to those unplanarized devices fabricated at higher temperature. Moreover, the simulation of the device using a SPICE model is presented.
The design and implementation of three analog median filter topologies, whose transistors operate in the deep weak-inversion region, is described. The first topology is a differential pairs array, in which drain currents are driven into two nodes in a differential fashion, while the second topology is based on a wide range OTA, which is used to maximize the dynamic range. Finally, the third topology uses three range-extended OTAs. The proposed weak-inversion filters were designed and fabricated in ON Semiconductor 0.5 µm technology through MOSIS. Experimental results of three-input fabricated prototypes for all three topologies are shown, with power consumptions of 90 nW in the first case, and 270 nW in the other two cases. A dual power supply ±1.5 Volts was used.
"We use the Höder regularity analysis to study the symmetry breaking and recovery due to a parametric potential generated via the strictly isospectral factorization method. The initial potential is two-dimensional and periodic in the two Cartesian directions, with the symmetry group
. The resulting parametric isospectral potential display a
symmetry for values of the parameter moderately close to the singular value
. However, at large values of the parameter, visually around
, the original symmetry is recovered. For a much higher precision value of the parameter for this symmetry recovery, we show that the multifractal spectrum of the parametric potential can be conveniently used. In the latter case, we obtain
for three decimal digits precision."
We report an all-fiber micro-displacement sensor based on multimode interference (MMI) effects. The micro-displacement sensor consists of a segment of No-Core multimode fiber (MMF) with one end spliced to a segment of single mode fiber (SMF) which acts as the input. The other end of the MMF and another SMF are inserted into a capillary ferrule filled with index matching liquid. Since the refractive index of the liquid is higher than that of the ferrule, a liquid MMF with a diameter of 125 μm is formed between the fibers inside the ferrule. When the fibers are separated this effectively increases the length of the MMF. Since the peak wavelength response of MMI devices is very sensitive to changes in the MMF’s length, this can be used to detect micro-displacements. By measuring spectral changes we have obtained a sensing range of 3 mm with a sensitivity of 25 nm mm−1 and a resolution of 20 μm. The sensor can also be used to monitor small displacements by using a single wavelength to interrogate the transmission of the MMI device close to the resonance peak. Under this latter regime we were able to obtain a sensitivity of 7000 mV mm−1 and a sensing range of 100 μm, with a resolution up to 1 μm. The simplicity and versatility of the sensor make it very suitable for many diverse applications.
We propose a set of photonic crystals that realize a nonlinear quantum Rabi model equivalent to a two-level system driven by the phase of a quantized electromagnetic field. The crystals are exactly solvable in the weak-coupling regime; their dispersion relation is discrete and the system is diagonalized by normal modes similar to a dressed state basis. In the strong-coupling regime, we use perturbation theory and find that the dispersion relation is continuous. We give the normal modes of the crystal in terms of continued fractions that are valid for any given parameter set. We show that these photonic crystals allow state reconstruction in the form of coherent oscillations in the weak-coupling regime. In the strong-coupling regime, the general case allows at most partial reconstruction of single waveguide input states, and non-symmetric coherent oscillations that show partial state reconstruction of particular phase-controlled states.
We show a right unitary transformation approach based on Susskind– Glogower operators that diagonalizes a generalized Dicke Hamiltonian in the field basis and delivers a tridiagonal Hamiltonian in the Dicke basis. This tridiagonal Hamiltonian is diagonalized by a set of orthogonal polynomials satisfying a three-term recurrence relation. Our result is used to deliver a closed form, analytic time evolution for the case of a Jaynes–Cummings–Kerr model and to study the time evolution of the population inversion, reduced field entropy, and Husimi’s Q-function of the field for ensembles of interacting two-level systems under a Dicke–Kerr model.
Héctor Manuel Moya Cessa (2013)
We propose a versatile approach for generating multipartite W states in predesigned on-chip multiport photonic lattices. It is shown that is possible to produce photon-encoded W states where exactly one photon is coherently “shared” among N optical modes by judiciously adjusting the coupling coefficients involved in one-dimensional arrays of evanescently coupled single-mode waveguides. Two-dimensional waveguide configurations are also investigated as possible avenues to produce W states with equal probability amplitudes and equal relative phases.