Nonlinear Nanoresonators Research Articles

Strain engineering of nonlinear nanoresonators from hardening to softening

Although strain engineering and soft-clamping techniques for attaining high Q-factors in nanoresonators have received much attention, their impact on nonlinear dynamics is not fully understood. In this study, we show that nonlinearity of high-Q Si3N4 nanomechanical string resonators can be substantially tuned by support design. Through careful engineering of support geometries, we control both stress and mechanical nonlinearities, effectively tuning nonlinear stiffness of two orders of magnitude. Our approach also allows control over the sign of the Duffing constant resulting in nonlinear softening of the mechanical mode that conventionally exhibits hardening behavior. We elucidate the influence of support design on the magnitude and trend of the nonlinearity using both analytical and finite element-based reduced-order models that validate our experimental findings. Our work provides evidence of the role of soft-clamping on the nonlinear dynamic response of nanoresonators, offering an alternative pathway for nullifying or enhancing nonlinearity in a reproducible and passive manner.

Nonlinear nanoresonators for Bell state generation

Entangled photon states are a fundamental resource for optical quantum technologies and investigating the fundamental predictions of quantum mechanics. Up to now such states are mainly generated in macroscopic nonlinear optical systems with elaborately tailored optical properties. In this theoretical work, we extend the understanding on the generation of entangled photonic states toward the nanoscale regime by investigating the fundamental properties of photon-pair generation in sub-wavelength nonlinear nanoresonators. Taking materials with Zinc-Blende structure as an example, we reveal that such systems can naturally generate various polarization-entangled Bell states over a very broad range of wavelengths and emission directions, with little to no engineering needed. Interestingly, we uncover different regimes of operation, where polarization-entangled photons can be generated with dependence on or complete independence from the pumping wavelength and polarization, and the modal content of the nanoresonator. Our work also shows the potential of nonlinear nanoresonators as miniaturized sources of biphoton states with highly complex and tunable properties.

Spectral responses of resonant dielectric metasurfaces induced by Kerr nonlinearity in pump-probe scheme: Theoretical study

In resonant nonlinear nanostructures, Kerr nonlinear responses and optical bistability have already been extensively studied. In spite of great importance, their spectral responses modified by the pump via nonlinear processes, however, have rarely been investigated. In this work, we analytically and numerically study the spectral responses of resonant dielectric metasurfaces induced by Kerr nonlinearity in pump-probe scheme, taking a gallium phosphide metasurface exhibiting strong resonance driven by quasi-bound states in the continuum, as an example. The intensity enhancement in the nonlinear nanoresonator at pump wavelength plays the central role in their nonlinear spectral responses: in the transmission spectrum obtained by scanning probe wavelength, the spectral position of resonance displays red-shift determined by the spectral profile of the enhancement modified by the pump, while the modulation depth of transmittance becomes shallower due to two-photon absorption. For further higher pump intensity, the metasurface exhibits hysteresis for the change of both intensity and wavelength of pump, resulting in spectral bistability. Comparison with numerical results shows that the analytical model based on nonlinear coupled-mode theory well describes their nonlinear spectral responses. The results can be served as theoretical tool for practical applications in characterizing their nonlinear responses and fabricating nonlinear photonic devices.

Far‐Field Polarization Engineering from Nonlinear Nanoresonators

AbstractNanoresonators fabricated from low‐loss dielectrics with second‐order nonlinearity have emerged as a widespread platform for nonlinear frequency conversion at the nanoscale. However, a persisting challenge in this research is the generated complex far‐field polarization state of the upconverted light, which is a limiting factor in many applications. It will be highly desirable to generate uniform far‐field polarization states across all propagation directions, to control the polarization truly along the optical axis and to simultaneously be able to tune the polarization along the entire circumference of the Poincaré sphere by solely modifying the excitation polarization. Here, a nonlinear nanoresonator combining all these properties is theoretically proposed and experimentally demonstrated. At first, an analytical model connecting the induced multipolar content of a nanoresonator with a desired far‐field polarization is derived. Based on this, a nonlinear dielectric nanoresonator is designed to enable sum‐frequency generation (SFG) with highly pure and tuneable far‐field polarization states. In the experiment, the nanoresonators fabricated from the III‐V semiconductor gallium arsenide in (110)‐orientation are excited in an SFG scheme with individually controllable excitation beams. The generation of highly uniform and tuneable far‐field polarization states is demonstrated by combining back‐focal plane measurements with Stokes polarimetry.

Nonlinearity in the Dark: Broadband Terahertz Generation with Extremely High Efficiency.

Plasmonic metamaterials and metasurfaces offer new opportunities in developing high performance terahertz emitters and detectors beyond the limitations of conventional nonlinear materials. However, simple meta-atoms for second-order nonlinear applications encounter fundamental trade-offs in the necessary symmetry breaking and local-field enhancement due to radiation damping that is inherent to the operating resonant mode and cannot be controlled separately. Here we present a novel concept that eliminates this restriction obstructing the improvement of terahertz generation efficiency in nonlinear metasurfaces based on metallic nanoresonators. This is achieved by combining a resonant dark-state metasurface, which locally drives nonlinear nanoresonators in the near field, with a specific spatial symmetry that enables destructive interference of the radiating linear moments of the nanoresonators, and perfect absorption via simultaneous electric and magnetic critical coupling of the pump radiation to the dark mode. Our proposal allows eliminating linear radiation damping, while maintaining constructive interference and effective radiation of the nonlinear components. We numerically demonstrate a giant second-order nonlinear susceptibility ∼10^{-11} m/V, a one order improvement compared with the previously reported split-ring-resonator metasurface, and correspondingly, a 2 orders of magnitude enhanced terahertz energy extraction should be expected with our configuration under the same conditions. Our study offers a paradigm of high efficiency tunable nonlinear metadevices and paves the way to revolutionary terahertz technologies and optoelectronic nanocircuitry.

Hysteresis assisted narrowband resonances in a chain of nonlinear plasmonic arrays

The plasmonic structures exhibiting narrowband resonances (NBR) are of a great interest for various applications. We propose to use hysteresis behavior in a 1D system of nonlinear nanoresonators in order to achieve the NRB; the nonlinearity is provided by saturation of a two-level quantum system coupled with the nanoresonators (nanolaser/spaser configuration). Quantum Dots (QD) were assumed as quantum systems; their numerical parameters have been adopted for estimations. Role of the loss compensation on the quality of the NBR is shown for below (under compensation) and above threshold (generating spasers) operation modes. Amplitude and phase detection schemes of the prospective experimental realization are compared using the developed model. Possible sensor oriented applications of the proposed system are discussed.

Near-field control of optical bistability in a nanocavity

Dynamic control of the optical bistability of a nonlinear nanoresonator is shown to be achievable by modifying the resonance of the optical cavity with a dielectric near-field tip. It is experimentally demonstrated that the operating regime of the nanocavity can be switched between monostable and bistable regimes. Finally, an analytical model is proposed which provides an adequate description of the properties of the whole nonlinear optomechanical system.

Chaos in a nonlinear damped Mathieu system, in a nano resonator system and in its fractional order systems

Abstract In this paper, the chaotic behaviors of a nonlinear damped Mathieu system and of a nonlinear nano resonator system with integral orders and with fractional orders are studied. By applying numerical analyses such as phase portraits, Poincare maps and bifurcation diagrams, the periodic and chaotic motions are observed. It is found that chaos exists both in the nonlinear damped Mathieu system and in the integral order and fractional order nano resonator systems.