Experimental evidence of Fano resonances in nanomechanical resonators

Replicating Spectral Baseline for Unambiguous Frequency Locking in Resonant Sensors

Electrothermal piezoresistive resonant cantilever sensors have been fabricated with embedded actuating (heating resistor) and sensing (piezo resistors) parts, with the latter configured in a Wheatstone bridge circuit. Due to the close spacing between these two elements, a direct thermal parasitic effect on the resonant sensor during the actuating-sensing process leads to asymmetric amplitude and reversing phase spectral responses. Such a condition affects the precise determination of the cantilever's resonant frequency, f0. Moreover, in the context of phase-locked loop-based (PLL) resonance tracking, a reversing phase spectral response hinders the resonance locking due to its ambiguity. In this work, a replica of the baseline spectral was applied to remove the thermal parasitic effect on the resonance spectra of the cantilever sensor, and its capability was simulated through mathematical analysis. This replica spectral was subtracted from the parasitized spectral using a particular calculation, resulting in optimized spectral responses. An assessment using cigarette smoke particles performed a desired spectral shifting into symmetrical amplitude shapes and monotonic phase transitions, subsequently allowing for real-time PLL-based frequency tracking.

Fluctuation relations for systems in a constant magnetic field

The validity of the fluctuation relations (FRs) for systems in a constant magnetic field is investigated. Recently introduced time-reversal symmetries that hold in the presence of static electric and magnetic fields and of deterministic thermostats are used to prove the transient FRs without invoking, as commonly done, inversion of the magnetic field. Steady-state FRs are also derived, under the t-mixing condition. These results extend the predictive power of important statistical mechanics relations. We illustrate this via the nonlinear response for the cumulants of the dissipation, showing how the alternative FRs enable one to determine analytically null cumulants also for systems in a single magnetic field.

Large-scale parallelization of nanomechanical mass spectrometry with weakly-coupled resonators

Nanomechanical mass spectrometry is a recent technological breakthrough that enables the real-time analysis of single molecules. In contraposition to its extreme mass sensitivity is a limited capture cross-section that can hinder measurements in a practical setting. Here we show that weak-coupling between devices in resonator arrays can be used in nanomechanical mass spectrometry to parallelize the measurement. This coupling gives rise to asymmetric amplitude peaks in the vibrational response of a single nanomechanical resonator of the array, which coincide with the natural frequencies of all other resonators in the same array. A rigorous theoretical model is derived that explains the physical mechanisms and describes the practical features of this parallelization. We demonstrate the significance of this parallelization through inertial imaging of analytes adsorbed to all resonators of an array, with the possibility of simultaneously detecting resonators placed at distances a hundred times larger than their own physical size.

Designing large-scale parallelization of nanomechanical array measurements remains elusive. Here, the authors propose weak-coupling between similar devices to evaluate the resonance frequencies of a whole resonator array with a single measurement.

Nanomechanical DNA resonators for sensing and structural analysis of DNA-ligand complexes

The effect of direct or indirect binding of intercalant molecules on DNA structure is of fundamental importance in understanding the biological functioning of DNA. Here we report on self-suspended DNA nanobundles as ultrasensitive nanomechanical resonators for structural studies of DNA-ligand complexes. Such vibrating nanostructures represent the smallest mechanical resonator entirely composed of DNA. A correlative analysis between the mechanical and structural properties is exploited to study the intrinsic changes of double strand DNA, when interacting with different intercalant molecules (YOYO-1 and GelRed) and a chemotherapeutic drug (Cisplatin), at different concentrations. Possible implications of our findings are related to the study of interaction mechanism of a wide category of molecules with DNA, and to further applications in medicine, such as optimal titration of chemotherapeutic drugs and environmental studies for the detection of heavy metals in human serum.

Strong vibrational coupling in room temperature plasmonic resonators

Strong vibrational coupling has been realized in a variety of mechanical systems. However, there have been no experimental observations of strong coupling of the acoustic modes of plasmonic nanostructures, due to rapid energy dissipation in these systems. Here we realized strong vibrational coupling in ultra-high frequency plasmonic nanoresonators by increasing the vibrational quality factors by an order of magnitude. We achieved the highest frequency quality factor products of f × Q = 1.0 × 10¹³ Hz for the fundamental mechanical modes, which exceeds the value of 0.6 × 10¹³ Hz required for ground state cooling. Avoided crossing was observed between vibrational modes of two plasmonic nanoresonators with a coupling rate of g = 7.5 ± 1.2 GHz, an order of magnitude larger than the dissipation rates. The intermodal strong coupling was consistent with theoretical calculations using a coupled oscillator model. Our results enabled a platform for future observation and control of the quantum behavior of phonon modes in metallic nanoparticles.

Strong vibrational coupling has not been observed in ultra-high frequency mechanical resonators. By engineering phonon dissipation pathways, the authors increase the vibrational quality factor to allow strong coupling observations in plasmonic nanostructures, which has implications for observation and control of quantum phonon dynamics.

Wideband excitation of Fano resonances and induced transparency by coherent interactions between Brillouin resonances

Wideband excitation and control of Fano resonance and electromagnetically induced transparency (EIT), both of which rely on coherent interaction between two excitation paths, is challenging. It requires precise control and tuning of interacting resonances or coupling between different resonant structures over a wide frequency range. Gain (Stokes) and absorption (anti-Stokes) resonances associated with the stimulated Brillouin scattering (SBS) process can be excited and controlled over a wide frequency range by tuning the pump frequency, its power and profile. We exploit coherent interaction between the Brillouin Stokes and anti-Stokes resonance, in radio frequency domain, to demonstrate Fano and EIT-like resonance over a wide frequency range and control their shape and strength optically and electrically. For the Fano resonance, the asymmetry and polarity are electrically controlled over an unprecedented frequency range (100 MHz-43 GHz) by varying the bias to the intensity modulator whereas, the strength is varied by tuning the Brillouin pump power and/or the bias. The depth and 3 dB linewidth of the transparency window in the EIT-like resonance are controlled using pump and probe parameters. The flexibility of the SBS process that allows wideband electrical and optical control of Fano and EIT-like resonance opens up the potential for applications that range from low-power switching, sensing to tunable RF delay.

Evolution of nanomechanical properties and crystallinity of individual titanium dioxide nanotube resonators

Herein a complete characterization of single TiO₂ nanotube resonator was reported for the first time. The modal vibration response analysis allows a non-invasive indirect evaluation of the mechanical properties of the TiO₂ nanotube. The effect of post-grown thermal treatments on nanotube mechanical properties was investigated and carefully correlated to the chemico-physical parameters evolution. The Young's modulus of TiO₂ nanotube rises linearly from 57 GPa up to 105 GPa for annealing at 600 °C depending on the compositional and crystallographic evolution of the nanostructure. Considering the growing interest in single nanostructure devices, the reported findings allow a deeper understanding of the properties of individual titanium dioxide nanotubes extrapolated from their standard arrayed architecture.