Adarsh Ganesan

Observation of three-mode parametric instability in a micromechanical resonator

We present systematic experimental observations of three-mode auto-parametric instability in a micromechanical resonator analogous to previous experimental observations of this effect in optical parametric resonators. The three-mode instability is triggered when a driven mode at frequency ωd couples to two lower frequency modes (frequencies ω1 and ω2) such that ωd = ω1 + ω2. Similar to the 2 mode instability, the phenomenon is seen to be threshold dependent and sensitive to driving conditions and system parameters. In support of the experimental observations, a dynamical model has also been specified.

Multifrequency acoustics as a probe of mesoscopic blood coagulation dynamics

Coagulation is a complex enzymatic polymerisation cascade. Disordered coagulation is common in medicine and may be life-threatening yet clinical assays are typically bulky and/or provide an incomplete picture of clot mechanical evolution. We present the adaptation of an in-plane acoustic wave device: quartz crystal microbalance with dissipation at multiple harmonics to determine the time-evolution of mesoscale mechanical properties of clot formation in vitro. This approach is sensitive to changes in surface and bulk clot structure in various models of induced coagulopathy. Furthermore, we are able to show that clot formation at surfaces has different kinetics and mechanical strength to that in the bulk, which may have implications for the design of bioprosthetic materials. The “Multifrequency acoustics” approach thus enables unique capability to portray biological processes concerning blood coagulation.

Frequency transitions in phononic four-wave mixing

This work builds upon the recent demonstration of a phononic four-wave mixing pathway mediated by parametric resonance. In such a process, drive tones fd1 and fd2 associated with a specific phonon mode interact such that one of the drive tones also parametrically excites a second mode at a sub-harmonic frequency and such interactions result in a frequency comb fd12±nfd1−fd2. However, the specific behaviour associated with the case where both drive tones can independently excite the sub-harmonic phonon mode has not been studied or previously described. While it may be plausible to expect the merger of two frequency combs fd12±nfd1−fd2 and fd22±nfd1−fd2, this paper indicates that only one of these mechanisms is selected and also shows an interesting transition linked to this process. The frequency transitions from fd12±nfd1−fd2 to fd22±nfd1−fd2 holds promise for computing applications.

Phononic frequency comb via three-mode parametric three-wave mixing

Optical frequency combs have resulted in significant advances in optical frequency metrology and found wide applications in precise physical measurements and molecular fingerprinting. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this Letter, we report the first clear experimental evidence for a phononic frequency comb. We show that the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an autoparametrically excited subharmonic mode. The experiments depict the comb generation process evidenced by a spectral response consisting of equally spaced discrete and phase coherent comb lines. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define the attributes to control the features associated with comb formation in such a system. In addition to the demonstration of frequency comb, the interplay between the nonlinear resonances and the well-known Duffing phenomenon is also observed.Optical frequency combs [1-8] have resulted in significant advances in optical frequency metrology and found wide application to precise physical measurements [1-4, 9] and molecular fingerprinting [8]. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this letter, we report the first clear experimental evidence for a phononic frequency comb. In contrast to the Kerr nonlinearity [10] in optical frequency comb formation, the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an auto-parametrically excited sub-harmonic mode [16]. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define attributes to control the features [17-18] associated with comb formation in such a system. Further, the interplay between these nonlinear resonances and the well-known Duffing phenomenon [12-14] is also observed. The presented pathway for phononic frequency comb formation finds general relevance to other nonlinear systems in both classical and quantum domains.

Excitation of multiple 2-mode parametric resonances by a single driven mode

We demonstrate autoparametric excitation of two distinct sub-harmonic mechanical modes by the same driven mechanical mode corresponding to different drive frequencies within its resonance dispersion band. This experimental observation is used to motivate a more general physical picture wherein multiple mechanical modes could be excited by the same driven primary mode within the same device as long as the frequency spacing between the sub-harmonic modes is less than half the dispersion bandwidth of the driven primary mode. The excitation of both modes is seen to be threshold-dependent and a parametric back-action is observed impacting on the response of the driven primary mode. Motivated by this experimental observation, modified dynamical equations specifying 2-mode auto-parametric excitation for such systems are presented.

Excitation of coupled phononic frequency combs via two-mode parametric three-wave mixing

This paper builds on the recent demonstration of three-wave mixing based phononic frequency comb. Here, in this process, an intrinsic coupling between the drive and resonant frequency leads to a frequency comb of spacing corresponding to the separation between drive and resonant frequency. In this paper, through the coupling with other identical devices, we demonstrate the emergence of two different frequency comb regimes using a single tone external drive signal. Several interesting features for coupled frequency combs are identified, including the following: (1) the spacing of the component frequency combs are controlled by two different resonant frequencies, each associated with two different modes; (2) the nonlinear drive level dependence is different for the component frequency combs; (3) mutually exclusive well-bounded regimes for each component frequency comb exist, and such regimes are not merely described by well-known parametric resonance thresholds.

Phononic frequency comb via three-mode parametric resonance

This paper is motivated by the recent demonstration of a phononic frequency comb. While previous experiments have shown the existence of a three-wave mixing pathway in a system of two-coupled phonon modes, this work demonstrates a similar pathway in a system of three-coupled phonon modes. This paper also presents a number of interesting experimental facts concomitant to the three-mode parametric resonance based frequency comb observed in a specific micromechanical device. The experimental validation of frequency combs via three-mode parametric resonance along with the previous demonstration of two-mode frequency combs points to the ultimate possibility of multimode frequency combs.

Hyperfine phononic frequency comb

Optical frequency combs have resulted in significant advances in optical frequency metrology and found wide applications in precise physical measurements and molecular fingerprinting. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this Letter, we report the first clear experimental evidence for a phononic frequency comb. We show that the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an autoparametrically excited subharmonic mode. The experiments depict the comb generation process evidenced by a spectral response consisting of equally spaced discrete and phase coherent comb lines. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define the attributes to control the features associated with comb formation in such a system. In addition to the demonstration of frequency comb, the interplay between the nonlinear resonances and the well-known Duffing phenomenon is also observed.Optical frequency combs [1-8] have resulted in significant advances in optical frequency metrology and found wide application to precise physical measurements [1-4, 9] and molecular fingerprinting [8]. A direct analogue of frequency combs in the phononic or acoustic domain has not been reported to date. In this letter, we report the first clear experimental evidence for a phononic frequency comb. In contrast to the Kerr nonlinearity [10] in optical frequency comb formation, the phononic frequency comb is generated through the intrinsic coupling of a driven phonon mode with an auto-parametrically excited sub-harmonic mode [16]. Through systematic experiments at different drive frequencies and amplitudes, we portray the well-connected process of phononic frequency comb formation and define attributes to control the features [17-18] associated with comb formation in such a system. Further, the interplay between these nonlinear resonances and the well-known Duffing phenomenon [12-14] is also observed. The presented pathway for phononic frequency comb formation finds general relevance to other nonlinear systems in both classical and quantum domains.

Coexistence of multiple multimode nonlinear mixing regimes in a microelectromechanical device

This paper builds on the recent demonstrations of two-mode three-wave mixing and three-mode four-wave mixing pathways. In these individual mixing mechanisms, the drive and resonant frequencies intrinsically couple to generate frequency combs with spacing defined by the separation between drive and resonant frequencies. Such frequency combs resulting from N-mode N + 1-wave mixing processes possess spectral characteristics which are strikingly different from those of nominal N-mode parametric resonances. Now, in this paper, we experimentally show the possibility to simultaneously trigger one N = N 1-mode N = N 1 + 1-wave mixing and one nominal N = N 2-mode parametric resonance through the significant drive of a single phonon mode. This specific demonstration, when set alongside previous studies, represents an important step towards understanding phononic frequency comb processes.

Low power sub-milligram resonant MEMS load sensor

A miniaturized resonant load sensor demonstrating sub-milligram sensitivity is presented. The sensor response is not limited by creep and hysteresis often observed in traditional load sensors. A prototype sensor demonstrates a resolution of 0.1 mg over a load range of 300 mg demonstrating excellent linearity over this range (R2=0.9998). An energy efficient front-end CMOS readout circuit consumes only 5 μW from a 1.2 V supply.