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Broadband homonuclear mixing pulses with low radiofrequency power are essential for NMR spectroscopy of proteins and small molecules, especially for emerging applications in high field NMR. We have analytically designed a mixing pulse with high bandwidth-to-power ratio, using our recently developed multi-frame method. Here, we compare the new pulse, NF4 (mixing in the fourth nutating frame), to the best currently available sequence, focusing on the low-power regime. We use simulations and experiments to compare the two pulses' relaxation properties and bandwidth, and demonstrate that NF4 has approximately 1.35 times higher bandwidth, with similar effective relaxation. Therefore, NF4 is a good choice for broadband homonuclear mixing, particularly when the available radiofrequency power is limited. [ABSTRACT FROM AUTHOR]

Upconversion of sub-bandgap photons is a promising approach to exceed the Shockley-Queisser limit in solar technologies. Calculations have indicated that ideal, upconverter-enhanced cell efficiencies can exceed 44% for non-concentrated sunlight, but such improvements have yet to be observed experimentally. To explain this discrepancy, we develop a thermodynamic model of an upconverter-cell considering a highly realistic narrow-band, non-unity-quantum-yield upconverter. As expected, solar cell efficiencies increase with increasing upconverter bandwidth and quantum yield, with maximum efficiency enhancements found for near-infrared upconverter absorption bands. Our model indicates that existing bimolecular and lanthanide-based upconverters will not improve cell efficiencies more than 1%, consistent with recent experiments. However, our calculations show that these upconverters can significantly increase cell efficiencies from 28% to over 34% with improved quantum yield, despite their narrow bandwidths. Our results highlight the interplay of absorption and quantum yield in upconversion, and provide a platform for optimizing future solar upconverter designs. [ABSTRACT FROM AUTHOR]

According to Edholm’s law, the demand for point-to-point bandwidth in wireless short-range communications has doubled every 18 months over the last 25 years. It can be predicted that data rates of around 5–10 Gb/s will be required in ten years. In order to achieve 10 Gb/s data rates, the carrier frequencies need to be increased beyond 100 GHz. Over the past ten years, several groups have considered the prospects of using sub-terahertz (THz) and THz waves (100–2000 GHz) as a means to transmit data wirelessly. Some of the reported advantages of THz communications links are inherently higher bandwidth compared to millimeter wave links, less susceptibility to scintillation effects than infrared wireless links, and the ability to use THz links for secure communications. Our goal of this paper is to provide a comprehensive review of wireless sub-THz and THz communications. [ABSTRACT FROM AUTHOR]

A high-sensitivity frequency domain laser based ultrasonic system is presented which uses a low power, amplitude modulated continuous wave (cw) laser source for acoustic wave generation. The acoustic signals are detected using a path stabilized Michelson interferometer coupled to a rf lock-in amplifier. The modulation frequency of the generation laser is scanned over the bandwidth of interest, and transient acoustic signals are reconstructed from the frequency domain data. The effects of measurement frequency resolution, bandwidth, and time domain aliasing on the reconstructed transient response are discussed. Experimental results on thin plates, where diffuse acoustic wave fields lasting several hundred microseconds are seen as a result of multiple reflections off of sample boundaries, demonstrate that the time domain signal can be unambiguously reconstructed through appropriate selection of frequency resolution. Time domain reconstructions of acoustic signals over a bandwidth of 200 MHz demonstrate the utility of the approach for acoustic microscopy; individual acoustic transients can be detected with extremely high signal to noise ratio and time gated for analysis. [ABSTRACT FROM AUTHOR]

The operation of a liquid polymer jet laser-plasma target and the characterization of the absolute x-ray emission in the extreme ultraviolet wavelength window from 9–19 nm is reported. The target is a liquid polymer (perfluoro-polyether) that is exposed to pulsed and focused laser light at 532 nm in the form of a thin, liquid microjet (d=40 to 160 μm) in vacuum. The spectral brightness of the source in the 13 nm range is relatively high because a large fraction of radiative energy is emitted in one single line only, which is assigned to be the 2p–3d FVII doublet at 12.8 nm, with a laser energy conversion efficiency of 0.45% (2π sr, 2% bandwidth) in our initial experiment. A further increase of the relative emission has been found in the wavelength range between 7 and 17 nm when the jet diameter was increased from 40 to 160 μm. The two-dimensional spatial profile of the source plasma (d=40 to 50 μm) has been analyzed with a pinhole camera. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A frequency-tunable current sensor consisting of Terfenol-D/PZT/Terfenol-D magnetoelectric (ME) laminate and Fe73.5Cu1Nb3Si13.5B9 nanocrystalline alloy has been developed. Almost all ME current-sensing devices have higher outputs at resonance conditions, but this advantage is useful only for narrow bandwidth. For the purpose of broadband current sensing, a frequency up-conversion mechanism is introduced by means of nonlinearity of the field-dependence magnetostriction λ(H). Current sensitivity enhancement is realized by modulating the low-frequency dynamic magnetostrictive strain to its resonance conditions. This solution provides the possibility to achieve resonance-enhanced sensitivity at the power-line frequency of 50 Hz, and the capability to immune the noise floor. Experimental results show that the modulated sensitivity is increased from 48.6mV/A to 178.4mV/A at 50Hz, and a small current step change of 3mA can be clearly distinguished by amplitude or phase of the output signals. These results provide possibilities to accurately detect weak currents in the noise ambient at low frequencies. [ABSTRACT FROM AUTHOR]

High data rate recording can be achieved using fast write drivers and fast heads. Advanced short-yoke write heads and write drivers with 450 ps rise time and programmable current overshoot were used to study recording at data rates up to 2 Gbit/s. The head flux rise time causes shifts of recorded transitions. It is well known that current overshoot helps to overcome bandwidth limitations in the write driver, interconnects, and write head. However, excessive overshoot may cause pattern-dependent transition shifts and significant distortions of recorded transitions. We present the data rate performance of short-yoke recording heads, analysis of nonlinear pattern-dependent distortions, and optimization of the write current wave form in the 1-2 Gbit/s range. Simple dibit and tribit patterns were recorded at 2 Gbit/s. Low-distortion recording for arbitrary data patterns was demonstrated at 1.6 Gbit/s after optimization of write current overshoot. [ABSTRACT FROM AUTHOR]

Two rectangular 1/3-octave passbands were derived from different spectral regions of everyday sentences, with the intelligibility of one band approximately twice the others. Both passbands were then filtered to produce a series of narrower rectangular passbands. Each of the original 1/3-octave passbands in turn served as the fixed bandwidth 'pedestal' and was paired with each of the series of narrower passbands of the other band. Remarkably, dual band intelligibilities were the same, regardless of which band served as pedestal, so the summed bandwidths determined intelligibility: The summed intelligibilities were irrelevant. Implications of this paradoxical 'summed bandwidth rule' are discussed. [ABSTRACT FROM AUTHOR]

We describe a mechanical vibration-based energy harvester deploying a flexible body beam to lower the spring constant of the device so that high-mode resonant frequencies are shifted down into a useable frequency range under natural environmental conditions. Whereas conventional cantilevers feature a single resonant frequency within this range, the proposed device generates multiple high-mode resonant frequencies in close proximity to form a wider operational bandwidth that is over 400% wider than that of conventional cantilever-type energy harvesters. [ABSTRACT FROM AUTHOR]

Introductory physics and astronomy courses commonly use Wien's displacement law to explain the colors of blackbodies, including the Sun and other stars, in terms of their temperatures. We argue here that focusing on the peak of the blackbody spectrum is misleading for three reasons. First, the Planck curve is too broad for an individual spectral color to stand out. Second, the location of the peak of the Planck curve depends on the choice of the independent variable in the plot. And third, Wien's displacement law is seldom used in actual practice to find a temperature and direct fitting to the Planck function is preferable. We discuss these flaws and argue that, at the introductory level, presentation of blackbody radiation in terms of photon statistics would be more effective pedagogically. The average energy of the emitted photons would then be presented in place of Wien's displacement law, and discussion of the Stefan-Boltzmann law would include the total number of photons emitted per second. Finally, we suggest that the Planck spectrum is most appropriately plotted as a "spectral energy density per fractional bandwidth distribution," using a logarithmic scale for the wavelength or frequency. [ABSTRACT FROM AUTHOR]

Broadband noise correlation methods for the passive extraction of information about the propagation of waves between distant sensor locations have received considerable attention in the literature. For the case of an isotropic ambient field distribution, there is a well-defined relationship between the expectation value of the wave coherence over the sensors and point-to-point wave propagation. Experimental applications, however, must contend with ambient field anisotropy as well as the performance limitations associated with stochastic fluctuations. This paper explores the influence of ambient field directionality on both (1) the connection between the measured wave coherence and sensor-to-sensor propagation and on (2) the rate at which measurements stochastically converge to the expectation value of the underlying wave coherence. Due to diffraction, the relationship between the measured wave coherence and sensor-to-sensor propagation is shown to be robust to even highly directional ambient field features. While the fluctuations of a stochastic system are generally known to depend on bandwidth and measurement duration, the rate of stochastic convergence depends additionally on the cross-spectral power density (coherent power) relative to the power-spectral density (total incident power). Practical experimental implications of these results are discussed. [ABSTRACT FROM AUTHOR]

Comprehensive characterization of wideband ultrasonic transducers and specifically optoacoustic detectors is achieved through the analysis of their frequency response as a function of the incident angle. The tests are performed under well-defined, repeatable operating conditions. Backillumination of a blackened, acoustically matched planar surface with a short laser pulse creates an acoustic impulse which is used as a wideband ultrasonic source. Upon illumination with a short laser pulse, the bandwidth of our source shows a -6 dB point of 12 MHz and a low-frequency roll-off around 300 kHz. Using proprietary software, we examine thoroughly the planarity of the emitted wave front within a specified amplitude cutoff and phase incoherence. Analysis of the angular dependence of the frequency response yields invaluable directivity information about the detector under study: a necessary component toward accurate optoacoustic image reconstruction and quantitative tomography. The laser ultrasonic source we developed is the main feature of our directivity measurement setup. Due to its simplicity, it can easily be adapted to various calibration devices. This paper focuses on the development and characterization of the flatness and the bandwidth of our wideband ultrasonic source. [ABSTRACT FROM AUTHOR]

Temporal weights used by listeners when judging the overall loudness of a stimulus were measured for a 1-s-long noise centered around 2 kHz, whose level was randomly perturbed every 100 ms. The bandwidth was either 6400 Hz (broadband condition) or 400 Hz (narrowband condition). The first 100 ms contributed significantly more than later segments to overall loudness perception in the broadband condition. The effect was significantly reduced in the narrowband condition which is in line with the hypothesis that a greater spectral loudness summation at stimulus onset might be the mechanism behind the onset accentuation. [ABSTRACT FROM AUTHOR]

Although the potential of using portable auditory evoked potential systems for field testing of stranded cetaceans has been long recognized, commercial systems for evoked potential measurements generally do not possess the bandwidth required for testing odontocete cetaceans and are not suitable for field use. As a result, there have been a number of efforts to develop portable evoked potential systems for field testing of cetaceans. This paper presents another such system, called the evoked response study tool (EVREST). EVREST is a Windows-based hardware/software system designed for calibrating sound stimuli and recording and analyzing transient and steady-state evoked potentials. The EVREST software features a graphical user interface, real-time analysis and visualization of recorded data, a variety of stimulus options, and a high level of automation. The system hardware is portable, rugged, battery-powered, and possesses a bandwidth that encompasses the audible range of echolocating odontocetes, making the system suitable for field testing of stranded or rehabilitating cetaceans. [ABSTRACT FROM AUTHOR]

A direct imaging algorithm for point and extended targets is presented. The algorithm is based on a physical factorization of the response matrix of a transducer array. The factorization is used to transform a passive target problem to an active source problem and to extract principal components (tones) in a phase consistent way. The multitone imaging function can superpose multiple tones (spatial diversity/aperture of the array) and frequencies (bandwidth of the probing signal) based on phase coherence. The method is a direct imaging algorithm that is simple and efficient since no forward solver or iteration is needed. Robustness of the algorithm with respect to noise is demonstrated via numerical examples. [ABSTRACT FROM AUTHOR]

Several experiments are described in which synthetic monophthongs from series varying between /i/ and /u/ are presented following filtered precursors. In addition to F2, target stimuli vary in spectral tilt by applying a filter that either raises or lowers the amplitudes of higher formants. Previous studies have shown that both of these spectral properties contribute to identification of these stimuli in isolation. However, in the present experiments we show that when a precursor sentence is processed by the same filter used to adjust spectral tilt in the target stimulus, listeners identify synthetic vowels on the basis of F2 alone. Conversely, when the precursor sentence is processed by a single-pole filter with center frequency and bandwidth identical to that of the F2 peak of the following vowel, listeners identify synthetic vowels on the basis of spectral tilt alone. These results show that listeners ignore spectral details that are unchanged in the acoustic context. Instead of identifying vowels on the basis of incorrect acoustic information, however (e.g., all vowels are heard as /i/ when second formant is perceptually ignored), listeners discriminate the vowel stimuli on the basis of the more informative spectral property. [ABSTRACT FROM AUTHOR]

It is well known that the spectral envelope is a perceptually salient attribute in musical instrument timbre perception. While a number of studies have explored discrimination thresholds for changes to the spectral envelope, the question of how sensitivity varies as a function of center frequency and bandwidth for musical instruments has yet to be addressed. In this paper a two-alternative forced-choice experiment was conducted to observe perceptual sensitivity to modifications made on trumpet, clarinet and viola sounds. The experiment involved attenuating 14 frequency bands for each instrument in order to determine discrimination thresholds as a function of center frequency and bandwidth. The results indicate that perceptual sensitivity is governed by the first few harmonics and sensitivity does not improve when extending the bandwidth any higher. However, sensitivity was found to decrease if changes were made only to the higher frequencies and continued to decrease as the distorted bandwidth was widened. The results are analyzed and discussed with respect to two other spectral envelope discrimination studies in the literature as well as what is predicted from a psychoacoustic model. [ABSTRACT FROM AUTHOR]

We report the concept and development of a Ka-band mode and polarization converter that efficiently converts a TE10 rectangular waveguide mode into either a linearly or a circularly polarized TE21 cylindrical waveguide mode. The converter is composed of a power-dividing section, a mode-converting section, and a polarization-transitioning section. The converting process in each section is displayed and the working principles are discussed. A prototype has been built and tested. The measured results agree well with the numerical calculations for both linear and circular polarizations. The measured optimum back-to-back transmission is 94% with a 1-dB bandwidth of 4.1 GHz for the linear polarization. As for the circular polarization, the measured optimum transmission is 97%, but the corresponding bandwidth is indistinct due to some resonant dips. The reasons and impact for the dips are discussed. A bandwidth of 3.9 GHz is obtained for a single circular converter; meanwhile, an approach to eliminating these unwanted dips is presented in theory. For further diagnostics, the field pattern of either polarization is directly displayed on a temperature-sensitive liquid crystal display sheet, where the electric field strength can be discerned from the color spectrum. In addition to high conversion efficiency and broad bandwidth, this converter features easy construction, high mode purity, and polarization controllability. [ABSTRACT FROM AUTHOR]

Utilizing a simple model in which the acoustic wave function is a sum of independent Gaussian wave packets, the relative intensity variance or scintillation index (SI) is analytically calculated. The model has an unspecified probability density function (PDF) for wave packet amplitudes and Gaussian PDFs for travel-time-induced and non-travel-time-induced phase shifts; amplitudes and both phase shifts are assumed to be mutually uncorrelated. It is shown that a proper treatment of the mean field is required to obtain the saturation value, SI=1, in the limit of a large number of interfering wave packets. The analytic formulas for SI allow identification of important wave packet parameters in the approach to saturation. Criteria are identified for both broadband and narrow-band cases for which the approach to saturation is from above and below 1. It is demonstrated that the broadband approach to saturation is much slower than the narrow-band cases, since wave packets separated in time by more than an inverse bandwidth do not strongly contribute to interference. This effect is quantified by the timebandwidth product. The model is also used to obtain an analytic expression for pulse time spread; it is shown that multipath conditions which favor a rapid approach to saturation do not favor large pulse spread. 2004 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

This study examines the annoyance of pure-tone and bandpass noises with center frequencies of 1000 and 2000 Hz under the condition of equal sound-pressure level. The bandwidths of the source signal were 0, 40, 80, 160, and 320 Hz, with a 2068-dB/octave sharp filter to control the autocorrelation function (ACF) of the source signal. Scale values of annoyance were obtained using a paired-comparison method. The results show that the annoyance of pure-tone and bandpass noises inside the critical band is not constant. The annoyance of pure tones is greater than that of sharply filtered noises within the critical band. The annoyance of bandpass noises increases with increasing effective duration of the ACF, te, which represents the repetitive feature or tonal component of the source signal within the critical band. 2004 Acoustical Society of America. [ABSTRACT FROM AUTHOR]

Radio-frequency (RF) atomic magnetometers (AMs) can be used in many applications, such as magnetic resonance imaging and nuclear quadrupole resonance. High-density AMs provide both superior sensitivity and large bandwidth. Previously, high-density potassium AMs were demonstrated, but these magnetometers have various disadvantages, such as high-temperature of operation and bulky design. We demonstrate a rubidium-87 RF AM with 5 fT/Hz1/2 sensitivity (3 fT Hz1/2 probe noise), which is comparable to that of the best potassium magnetometers. Our magnetometer also features a simple fiber-optic design, providing maximum flexibility for magnetic-field measurements. [ABSTRACT FROM AUTHOR]

We describe a heterogeneous terahertz (THz) quantum cascade laser that is composed of two different active region designs. This device emits simultaneously at around 2.5 and 2.9 THz with certain frequency tunability by applied current. We also investigate the spectral gain in the structure by THz time-domain spectroscopy and correlate the gain spectral bandwidth with the alignment and wavelength emission behavior of the two stack device. [ABSTRACT FROM AUTHOR]

We demonstrate the experimental realization of an invisibility cloak based on inductor-capacitor (L-C) transmission line (TL) networks. The anisotropic medium parameters of a cloak in the cylindrical basis are controlled independently by three branches of the L-C unit cell, which leads to a full-parameter realization of the cloak. A cylindrical cloak working in very-high-frequency band has been designed and fabricated, with its performance measured. The nonresonant property of the TL structure results in a relatively broad bandwidth (from 24 to 40 MHz) of the realized cloak, which is clearly observed in our experiment. [ABSTRACT FROM AUTHOR]

A prevalent mode of optical tweezers involves position clamping that regulates a constant position of a trapped bead. Traditional schemes employ the measured bead position in the open loop or the control signal in the position-clamp mode as an estimate of external force on the trapped bead. This article shows that traditional methods introduce fundamental limitations on bandwidth of the external force estimation. A method is presented that leads to an order of magnitude increase in the bandwidth of the external force estimation. Furthermore, a comprehensive modeling paradigm is introduced that facilitates estimation of forces on the bead. [ABSTRACT FROM AUTHOR]

The authors report the demonstration of the bandgap-tuned InAs quantum dash broadband laser with widened laser emission linewidth at room temperature using postgrowth intermixing technique. The 100 nm wavelength blueshifted, as-cleaved laser exhibits ultrabroad lasing spectral coverage of ∼85 nm at a center wavelength of 1.54 μm with a total emission power of ∼1 W per device. Compared to the as-grown laser, this laser shows broader lasing bandwidth (∼41 nm) with improved spectral ripple (<1 dB). [ABSTRACT FROM AUTHOR]

We report the use of the photothermal actuation for the self-excitation of a selected vibration mode of a microcantilever in liquid. The gain of the positive feedback loop is adjusted in order to obtain a negative effective damping. In this regime, the amplitude noise is squeezed due to the nonlinear saturation of the system and the phase noise is largely reduced. The microcantilever vibration achieved a frequency stability of the order of 1 ppm for a bandwidth of 1 Hz. This is at least two orders of magnitude better than previous measurements in liquids. The obtained sensitivity is applied for detecting in real time the change of the fluid properties when glycerol is added to water at a concentration of 1% (m/m). [ABSTRACT FROM AUTHOR]

This letter reports on broadband laser sources based on InGaAs tapered diode laser amplifiers with external optical feedback. The generated 920 nm radiation with a bandwidth of up to 20 nm and a power of a few hundred milliwatts is emitted in an almost diffraction limited beam. Spectral filtering and subsequent amplification in a second tapered amplifier provides radiation with spectral widths in the range of 20 to 40 nm and optical output powers of up to 2.5 W. [ABSTRACT FROM AUTHOR]

Heterodyne mixing characteristics of a double-quantum-well field-effect transistor (DQW FET) from 94 to 145 GHz are reported. The DQW FET exhibits two physically distinct mixing responses. Near pinch-off, the device behaves as a broadband bolometric mixer with intermediate frequency (IF) bandwidth of 620 MHz. Away from pinch-off it shows an electrically tunable resonant plasmon response. Mixing on a plasmon resonance yields an IF with significant harmonic distortion, signaling a complicated nonlinear mechanism, and shows a wide IF bandwidth >2 GHz. [ABSTRACT FROM AUTHOR]

Efficient second-harmonic generation of 95 fs pulses were achieved by simultaneous group-velocity matching and quasi-phase matching in a 10 mm long periodically poled potassium niobate crystal. The quasi-phase-matched bandwidth was 38 nm and second-harmonic pulse duration was 158 fs with a fundamental input pulse of 95 fs without spectral and temporal distortion in the S-band of telecommunication. Utilizing the larger off-diagonal nonlinear coefficient, d31 of potassium niobate, the conversion efficiency was significantly improved from that of periodically poled MgO-doped lithium niobate. [Appl. Phys. Lett. 82, 3388 (2003)] [ABSTRACT FROM AUTHOR]

Efficient second-harmonic generation of 95 fs pulses were achieved by simultaneous group-velocity matching and quasi-phase matching in a 10 mm long periodically poled potassium niobate crystal. The quasi-phase-matched bandwidth was 38 nm and second-harmonic pulse duration was 158 fs with a fundamental input pulse of 95 fs without spectral and temporal distortion in the S-band of telecommunication. Utilizing the larger off-diagonal nonlinear coefficient, d31 of potassium niobate, the conversion efficiency was significantly improved from that of periodically poled MgO-doped lithium niobate. [Appl. Phys. Lett. 82, 3388 (2003)] [ABSTRACT FROM AUTHOR]

Field-resolved detection of ultrabroadband infrared pulses is implemented with GaSe crystals. Via phase matching, we extend the detectable frequency range toward the near infrared (λ=2.5 μm) and directly record transform-limited pulses as short as 28 fs with a 3 dB bandwidth of 41 THz. The continuous tunability of the center frequency over a wide interval ranging from 31 THz to the far-infrared is demonstrated using thick sensors. [ABSTRACT FROM AUTHOR]

The National Ignition Facility at the Lawrence Livermore National Laboratory requires high bandwidth and high dynamic range data transmission from the target chamber area to diagnostic recording equipment approximately 46 m away. The systems need to pass short pulse signals with high fidelity, requiring a broadband frequency response from below 10 MHz to greater than 6 GHz, that has flat amplitude and a linear phase response. We present here the characterization of a few selected fiber optic systems and work done to optimize the performance of a fiber link and single-shot transient digitizer system. Each link is evaluated by its bandwidth, the fidelity of its step response, the signal loss, and its usable dynamic range. [ABSTRACT FROM AUTHOR]

We report experimental results of using GaSe crystals for the broadband detection of terahertz (THz) waves from 100 GHz to 30 THz. In comparison, the THz wave field amplitude measured with a GaSe crystal exceeds that detected by a ZnTe crystal with a comparable detection bandwidth. The central frequency is tunable by varying the angle between the incident THz radiation and the crystal surface normal. [ABSTRACT FROM AUTHOR]

We report the demonstration of a planar THz interconnect layer capable of transmitting subpicosecond pulses in the transverse electromagnetic (TEM) mode over arbitrarily long paths with low absorption and no observable group velocity dispersion. Quasioptical elements are incorporated within the interconnect layer forming a configurable THz bandwidth TEM-mode planar interconnect with negligible group velocity dispersion and low loss. For a 146 mm guided path length, including four reflections, the pulses are broadened by the frequency dependent absorption of the interconnect layer from 0.28 to 0.32 ps, and attenuated by the factor 0.2. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied small signal frequency response of a spin laser. We have shown that the response is characterized by two distinct resonant peaks corresponding to the two polarization modes of the spin laser. It is observed that the modulation bandwidth of a spin laser can be smaller or larger than that of a conventional laser depending upon the current bias and spin relaxation time constant. A small value for spin relaxation constant may not be detrimental for modulation bandwidth. This anomalous observation is explained by considering both the amplitude and phase response of the two polarization modes. A spin laser can act as a combination of low-pass and bandpass filters. The passband frequency range is tunable by external bias. We have also studied the evolution of resonant peaks and modulation bandwidth as a function of spin relaxation time constant. [ABSTRACT FROM AUTHOR]

We report single-shot readout of a superconducting flux qubit by using a flux-driven Josephson parametric amplifier (JPA). After optimizing the readout power, gain of the JPA, and timing of the data acquisition, we observe the Rabi oscillations with a contrast of 74%, which is mainly limited by the bandwidth of the JPA and the energy relaxation of the qubit. The observation of quantum jumps between the qubit eigenstates under continuous monitoring indicates the nondestructiveness of the readout scheme. [ABSTRACT FROM AUTHOR]

This study demonstrates an adiabatic fiber microtaper with incorporated an air-gap microcavity fiber-Fabry-Pérot-interferometer to perform superior sensing characteristics. Optical interference fringes with good fringes contrast within bandwidth of 1250-1650 nm are performed experimentally. A highly spectral sensitivity of peak power with +3.65 dB/ °C (+9759 dB/RIU) is achieved when the device is operated under a fundamental-mode-cutoff (FMC) condition. By measuring peak power of the fringe, one can determine the temperature (T) or refractive index of environment. The proposed hybrid sensor is further applied to measure high T (∼1000 °C) of surrounding in non-FMC condition that obtains a good linearity of spectral response. [ABSTRACT FROM AUTHOR]

Broadband wave filtering effect is observed in a phononic crystal with hierarchical structure inspired by biocomposites. Through a multilayered model with hierarchical structure, it is demonstrated that the overall bandwidth covered by closely adjacent bandgaps for this structure is orders of magnitude broader in frequency than that of conventional periodic structure with single periodicity. This remarkable feature is attributed to the inherent multiscale periodicity in the microstructure, which roughly superimposes the bandgaps generated by individual periodic structures with periods corresponding to those at different hierarchies in the hierarchical structure. [ABSTRACT FROM AUTHOR]

We report on ultrafast GaN/AlGaN waveguide quantum cascade detectors with a peak detection wavelength of 1.5 μm. Mesa devices with a size of 7 × 7 and 10 × 10 μm2 have been fabricated with radio-frequency impedance-matched access lines. A strong enhancement of the responsivity is reported by illuminating the waveguide facet, with respect to illumination of the top surface. The room temperature responsivity is estimated to be higher than 9.5 ± 2 and 7.8 ± 2 mA/W, while the -3dB frequency response is extracted to be 42 and 37.4 GHz for 7 × 7 and 10 × 10 μm2 devices, respectively. [ABSTRACT FROM AUTHOR]

Binaural masking patterns show a steep decrease in the binaural masking-level difference (BMLD) when masker and signal have no frequency component in common. Experimental threshold data are presented together with model simulations for a diotic masker centered at 250 or 500 Hz and a bandwidth of 10 or 100 Hz masking a sinusoid interaurally in phase (S0) or in antiphase (Sπ). Simulations with a binaural model, including a modulation filterbank for the monaural analysis, indicate that a large portion of the decrease in the BMLD in remote-masking conditions may be due to an additional modulation cue available for monaural detection. [ABSTRACT FROM AUTHOR]