The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform
J.c. Cartledge - One of the best experts on this subject based on the ideXlab platform.
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Influence of mode competition on the fast wavelength switching of three-section DBR lasers
IEEE Photonics Technology Letters, 1993Co-Authors: L. Zhang, J.c. CartledgeAbstract:For a three-section distributed Bragg reflector (DBR) laser, the dependence of the intermodal wavelength-switching time on the precise wavelengths within two longitudinal modes is examined experimentally and theoretically. When switching from a fixed wavelength in the central region of the Tuning Curve for one mode to a second wavelength on the Tuning Curve for another mode, a significant variation of the switching delay occurs as the second wavelength spans the mode Tuning Curve. Mode competition is identified as being responsible for this variation.
Marcelo O Magnasco - One of the best experts on this subject based on the ideXlab platform.
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a wave traveling over a hopf instability shapes the cochlear Tuning Curve
Physical Review Letters, 2003Co-Authors: Marcelo O MagnascoAbstract:The Tuning Curve of the cochlea measures how intense an input is required to elicit a given output level as a function of the frequency. It is a fundamental object of auditory theory, for it summarizes how to identify sounds on the basis of the cochlear output. A simple model is presented showing that only two elements are sufficient for establishing the cochlear Tuning Curve: a broadly tuned traveling wave, moving unidirectionally from high to low frequencies, and a set of mechanosensors poised at the threshold of an oscillatory (Hopf) instability. These two components generate the various frequency-response regimes needed for a cochlear Tuning Curve with a high slope.
T. Feurer - One of the best experts on this subject based on the ideXlab platform.
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Tuning Curve of type-0 spontaneous parametric down-conversion
2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE IQEC, 2013Co-Authors: S. Lerch, B. Bessire, C. Bernhard, A. Stefanov, T. FeurerAbstract:The understanding of the spatiotemporal structure of the spectrum is of importance for all applications where entanglement in energy is the relevant degree of freedom and allows optimizing the spectrum for specific applications. Here, we consider spontaneous parametric down-conversion (SPDC) induced by an undepleted monochromatic pump beam of angular frequency ωρ with a transverse field distribution εp+(qp), which propagates along the z-axis of a periodically poled potassium titanyl phosphate (PPKTP) crystal. The pump photon (p) is down-converted into the idler (i) and signal (s) photon with frequency ω; = ωρ - ωs and ωs, respectively.
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Tuning Curve of type 0 spontaneous parametric down conversion
International Quantum Electronics Conference, 2013Co-Authors: S. Lerch, B. Bessire, C. Bernhard, A. Stefanov, T. FeurerAbstract:The understanding of the spatiotemporal structure of the spectrum is of importance for all applications where entanglement in energy is the relevant degree of freedom and allows optimizing the spectrum for specific applications. Here, we consider spontaneous parametric down-conversion (SPDC) induced by an undepleted monochromatic pump beam of angular frequency ωρ with a transverse field distribution ep+(qp), which propagates along the z-axis of a periodically poled potassium titanyl phosphate (PPKTP) crystal. The pump photon (p) is down-converted into the idler (i) and signal (s) photon with frequency ω; = ωρ - ωs and ωs, respectively.
L. Zhang - One of the best experts on this subject based on the ideXlab platform.
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Influence of mode competition on the fast wavelength switching of three-section DBR lasers
IEEE Photonics Technology Letters, 1993Co-Authors: L. Zhang, J.c. CartledgeAbstract:For a three-section distributed Bragg reflector (DBR) laser, the dependence of the intermodal wavelength-switching time on the precise wavelengths within two longitudinal modes is examined experimentally and theoretically. When switching from a fixed wavelength in the central region of the Tuning Curve for one mode to a second wavelength on the Tuning Curve for another mode, a significant variation of the switching delay occurs as the second wavelength spans the mode Tuning Curve. Mode competition is identified as being responsible for this variation.
Murray S Korman - One of the best experts on this subject based on the ideXlab platform.
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nonlinear Tuning Curve demonstration comparing a buried mine simulant with a clamped elastic plate cylindrical soil column oscillator
Journal of the Acoustical Society of America, 2019Co-Authors: Ava B Twitty, Murray S KormanAbstract:Experiments using soil-plate-oscillators (SPO) involve a cylindrical column of granular media (masonry sand) supported by a clamped circular elastic acrylic plate (12.7 cm diameter, 3.2 mm thick). The plate is clamped between two 20.3 cm O.D., 12.7 cm I.D., 6.4 cm thick flat toroidal brass “rings.” Two 15 cm diameter subwoofers (10 cm above the soil) are driven by an amplified swept sinusoidal chirp which drives the 2.5-cm soil column. A spectrum analyzer measures the laser Doppler vibrometer particle velocity versus frequency near the center of the column. The resonant frequency decreases with the increasing amplitude—representing softening in the nonlinear system. The back-bone Curve (locus of the resonant frequency versus corresponding peak velocity coordinates) has a distinct arching shape where the slope of the velocity increases with the decreasing frequency. Here, the resonant frequency goes from 247 to 203 Hz. A lumped element bilinear hysteresis model describes the shape of the Tuning Curves and backbone Curve. Next, a drum-like simulant (made by replacing the upper toroidal ring by a 0.64-cm thick ring) is buried 2.5-cm deep in an open square concrete tank (57 cm). Nonlinear Tuning Curve experiments “on” and “off” the mine are compared with the SPO results. Experiments using soil-plate-oscillators (SPO) involve a cylindrical column of granular media (masonry sand) supported by a clamped circular elastic acrylic plate (12.7 cm diameter, 3.2 mm thick). The plate is clamped between two 20.3 cm O.D., 12.7 cm I.D., 6.4 cm thick flat toroidal brass “rings.” Two 15 cm diameter subwoofers (10 cm above the soil) are driven by an amplified swept sinusoidal chirp which drives the 2.5-cm soil column. A spectrum analyzer measures the laser Doppler vibrometer particle velocity versus frequency near the center of the column. The resonant frequency decreases with the increasing amplitude—representing softening in the nonlinear system. The back-bone Curve (locus of the resonant frequency versus corresponding peak velocity coordinates) has a distinct arching shape where the slope of the velocity increases with the decreasing frequency. Here, the resonant frequency goes from 247 to 203 Hz. A lumped element bilinear hysteresis model describes the shape of the Tuning Curves and ...
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classroom demonstration of nonlinear Tuning Curve vibration and two tone tests using a column of glass beads vibrating over a clamped elastic plate
Journal of the Acoustical Society of America, 2018Co-Authors: Emily V Santos, Murray S KormanAbstract:A soil plate oscillator (SPO) apparatus consists of two circular flanges sandwiching and clamping a thin circular elastic plate. The apparatus can model the acoustic landmine detection problem. Here, uniform spherical glass beads—representing a nonlinear mesoscopic elastic material—are supported at the bottom by the acrylic plate (4.5 inch diam, 1/8 inch thick) and stiff cylindrical sidewalls of the upper flange. A magnetic disk centered and fastened below the plate is driven by an AC coil placed below the magnet. Nonlinear Tuning Curves of the magnet’s acceleration are measured by driving the coil with a swept sinusoidal signal applied to a constant current amplifier. Ten (separate) Tuning Curve experiments are performed using a fixed column of 350 grams of beads using 1,2,3,…,10 mm diameter beads. The backbone Curves (peak acceleration vs. corresponding resonant frequency) exhibit a linear region with comparable slopes, while the detailed curvature vs. bead diameter reveals more structure. A bilinear hy...
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demonstration of nonlinear Tuning Curve vibration of granular medium supported by a clamped circular elastic plate using a soil plate oscillator
Journal of the Acoustical Society of America, 2017Co-Authors: Emily V Santos, Murray S KormanAbstract:A demonstration will be conducted in order to show how a soil plate oscillator (SPO) filled with granular material will create a nonlinear system due to shifting peaks in a Tuning Curve with incremental increases in the swept drive amplitude. An SPO has two flanges clamping an elastic plate which supports a circular column of granular material. The plate (with a magnet and accelerometer fastened to the underside) is driven below by an amplified swept sinusoidal current applied to an AC coil. Past results have used masonry sand, granular edible uncooked materials, and glass beads in order to study the nonlinear Tuning Curve response near a resonance with (1) a fixed soil column while changing drive amplitude and (2) mass loading of a soil column versus the resonant frequency response of the system at a fixed drive amplitude. When the experiments are performed at a fixed drive but with a changing mass layer the resonant frequency increases then decreases with increased added mass due to an increase in flexu...
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nonlinear experiments of Tuning Curve resonances for the vibrational modes of a weakly stretched circular membrane
Journal of the Acoustical Society of America, 2014Co-Authors: Benjamin W Lloyd, Murray S KormanAbstract:Nonlinear oscillations of a pre-stretched 11.5 cm diameter latex circular membrane clamped rigidly around the boundary were investigated. The relaxed membrane thickness was 0.4 mm. An 8 cm diameter loud speaker drove the membrane from below using a swept sinusoidal tone. Low drive Tuning Curve sweeps demonstrated resonant frequencies corresponded to the first three radially symmetric linear drum modes (56, 147.6, and 240.5 Hz) sweeping from 50 to 300 Hz. Regression yielded a transverse wave speed of 10.6 m/s. Incrementally increasing the speaker amplitude (after each sweep) showed the lowest resonant frequency at first decreases, then increases with increasing acoustic drive pressure. Higher modes exhibited frequency increases with drive level. Tuning Curve responses were measured using a 6 mm diameter microphone 5 mm above the center of the membrane. Nonlinear Tuning Curves hysteresis effects occur for higher drive levels sweeping between 50 and 70 Hz. Here, the amplitude sharply falls from a high to a low microphone response at fa = 59 Hz. With the same drive level, a sweep tone starting from 70 Hz to 50 Hz exhibits at fa = 57.5 Hz, a jump from a lower to a higher microphone response. [Goncalves et al., J. Vib. Sound 327, 231 (2009).]
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nonlinear Tuning Curve vibration response of a buried landmine
International Conference on Multimedia Information Networking and Security, 2003Co-Authors: James M Sabatier, Murray S KormanAbstract:Measurements of the acoustic impedance of a VS 2.2 anti-tank plastic landmine reveal significant resonances in the frequency range between 80 and 650 Hz. The top surface resonances are due to its complicated mechanical structure vibrating in air. The lowest mode of the landmine results in a high Q simple harmonic oscillator resonance of the top surface, which behaves like a rigid mass. At higher frequencies the top surface behaves like thin circular plat acoustic modes. When these landmines are buried in soils, the modes are mass loaded. Resonances from measurements of the normal component of the acoustically induced soil surface particle velocity (due to sufficient acoustic-to-seismic coupling) are used for detection schemes. Since the interface between the top plate and the soil responds to pressure fluctuations nonlinearly, characteristics of landmines, the soil, and the interface are rich in nonlinear physics and allow for new methods of buried landmine detection not previously exploited. Here, the structure of a family of resonant Tuning Curves for relatively low amplitude, but nonlinear drive levels, reveals the “nonclassical” nonlinear resonant behavior of the soil-landmine oscillator.
