arXiv subjects

Ashwin Seshia

Publications and source records attributed to Ashwin Seshia.

6 recordsLinked to original sources

arXiv2017

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. Now, in this paper, we experimentally demonstrate the possibility to further excite multiple frequency combs with the same external drive through its coupling with other identical devices. In addition, we also experimentally identify interesting features associated with such a frequency comb generation process.

physics.app-ph↗

arXiv2017

Towards N-mode parametric electromechanical resonances

The ubiquity of parametric resonance is continually evident in the repeated experimental observations of this phenomenon in multiple physical systems. The elementary case of 2 mode parametric resonance of order 1 involves the excitation of a spectral tone of a parametrically driven mode at a sub-harmonic frequency of the higher directly driven mode. Historically, such examples of parametric resonance have been predominantly researched in a system of micro- and nanoelectromechanical resonators. Here, in this paper, we break this convention by showcasing a collection of experimental signatures in support of the concept of "N-mode parametric resonance" using a number of elementary microelectromechanical devices. Specifically, we present observations of 2, 3, (2+3) and (3+3) mode parametric resonances demonstrating co-existence of different regimes within the same device. In addition, we also present observations of intrinsic "Four-Wave Mixing" of parametric excitations. This paper presents contributions towards the existence proof for such multimode parametric resonances which can also be exploited for engineering benefit within the field of "micro and nanoelectromechanical resonators". The experimental results further point towards the possibility of the ultimate observation of N-mode parametric resonance in such physical system.

physics.class-ph↗

arXiv2017

Frequency transitions in phononic four-wave mixing

This work builds upon the recent demonstration of a phononic four-wave mixing (FWM) pathway mediated by parametric resonance. In such a process, drive tones f_d1 and f_d2 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 f_d1/2 +/- n(f_d1-f_d2 ). 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 possible to expect the merger of two frequency combs f_d1/2 +/- n(f_d1-f_d2 ) and f_d2/2 +/- n(f_d1-f_d2 ), this paper indicates that only one of these mechanisms is selected and also shows an interesting transition linked to this process. Such frequency transitions from f_d1/2 +/- n(f_d1-f_d2 ) to f_d2/2 +/- n(f_d1-f_d2 ) holds potential promise for computing applications.

nlin.PS↗

arXiv2017

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.

nlin.PS↗

arXiv2016

Anomaly in coupled parametric resonance

We present experimental observations of an anomaly in the coupled response of auto-parametrically excited microelectromechanical beams. When one of the two coupled beams is driven at elevated amplitudes, the excitation of dominant and recessive modes is observed in the driven and non-driven beams respectively. This anomalous nature of auto-parametric excitation has been unexplored by both theory and experiments and falls outside the scope of the conventional description of parametric resonance.

nlin.PS↗

arXiv2016

Hyperfine phononic frequency comb

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.

nlin.PS↗