Oleg Shtempluck

Signal amplification in a nanomechanical Duffing resonator via stochastic resonance

The authors experimentally study stochastic resonance in a nonlinear bistable nanomechanical doubly clamped beam resonator, which is capacitively excited by an adjacent gate electrode. The resonator is tuned to its bistability region by an intense pump near a point of equal transition rates between its two metastable states. The pump is amplitude modulated, inducing modulation of the activation barrier between the states. When noise is added to the excitation, resonator’s displacement exhibits noise dependent amplification of the modulation signal. They measure resonator’s response in the time and frequency domains, the spectral amplification, and the statistical distribution of the jump time.

Noise squeezing in a nanomechanical duffing resonator

We study mechanical amplification and noise squeezing in a nonlinear nanomechanical resonator driven by an intense pump near its dynamical bifurcation point, namely, the onset of Duffing bistability. Phase sensitive amplification is achieved by a homodyne detection scheme, where the displacement detectors output, which has a correlated spectrum around the pump frequency, is down-converted by mixing with a local oscillator operating at the pump frequency with an adjustable phase. The down-converted signal at the mixers output could be either amplified or deamplified, yielding noise squeezing, depending on the local oscillator phase.

Performance of an AuPd micromechanical resonator as a temperature sensor

In this work we study the sensitivity of the primary resonance of an electrically excited microresonator for the possible usage of a temperature sensor. We find a relatively high normalized responsivity factor Rf=|TfdfdT|=0.37 with a quality factor of ∼105. To understand this outcome we perform a theoretical analysis based on experimental observation. We find that the dominant contribution to the responsivity comes from the temperature dependence of the tension in the beam. Subsequently, Rf is found to be inversely proportional to the initial tension. Corresponding to a particular temperature, the tension can be increased by applying a bias voltage.

Nonlinear dynamics in the resonance line shape of NbN superconducting resonators

In this work we characterize the unusual nonlinear dynamics of the resonance response, exhibited by our NbN superconducting microwave resonators, using different operating conditions. The nonlinear dynamics, occurring at relatively low input powers (2-4 orders of magnitude lower than Nb), and which include among others, bifurcations in the resonance curve, hysteresis loops and resonance frequency shift, are measured herein using varying temperature, applied magnetic field, white noise and rapid frequency sweeps. Based on these measurement results, we consider a hypothesis according to which Josephson junctions forming weak links at the boundaries of the NbN grains are responsible for the observed behavior, and we show that most of the experimental results are qualitatively consistent with such hypothesis.We report on unusual nonlinear dynamics observed in the resonance response of

High intermodulation gain in a micromechanical Duffing resonator

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Forced and self-excited oscillations of an optomechanical cavity.

superconducting microwave resonators. The nonlinear dynamics which occurs at relatively low input powers (2\char21{}4 orders of magnitude lower than Nb) includes among others, jumps in the resonance line shape, hysteresis loops changing direction, and resonance frequency shift. These effects are measured herein using varying input power, applied magnetic field, white noise, and rapid frequency sweeps. Based on these measurement results, we consider a hypothesis according to which local heating of weak links forming at the boundaries of the

Noise-induced intermittency in a superconducting microwave resonator

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Observation of Bifurcations and Hysteresis in Nonlinear NbN Superconducting Microwave Resonators

grains is responsible for the observed behavior, and we show that most of the experimental results are qualitatively consistent with such a hypothesis.

Intermodulation gain in nonlinear NbN superconducting microwave resonators

In this work we use a micromechanical resonator to experimentally study small signal amplification near the onset of Duffing bistability. The device consists of a PdAu beam serving as a micromechanical resonator excited by an adjacent gate electrode. A large pump signal drives the resonator near the onset of bistability, enabling amplification of small signals in a narrow bandwidth. To first order, the amplification is inversely proportional to the frequency difference between the pump and the signal. We estimate the gain to be about 15dB for our device.

Thermal instability and self-sustained modulation in superconducting NbN stripline resonators

We experimentally study forced and self-excited oscillations of an optomechanical cavity, which is formed between a fiber Bragg grating that serves as a static mirror and a freely suspended metallic mechanical resonator that serves as a moving mirror. In the domain of small amplitude mechanical oscillations, we find that the optomechanical coupling is manifested as changes in the effective resonance frequency, damping rate, and cubic nonlinearity of the mechanical resonator. Moreover, self-excited oscillations of the micromechanical mirror are observed above a certain optical power threshold. A comparison between the experimental results and a theoretical model that we have recently derived and analyzed yields a good agreement. The comparison also indicates that the dominant optomechanical coupling mechanism is the heating of the metallic mirror due to optical absorption.