Low-Power Photothermal Self-Oscillation of Bimetallic Nanowires

Roberto De Alba, T. S. Abhilash, Richard H. Rand, Harold G. Craighead, Jeevak M. Parpia

Research output: Contribution to journalArticleScientificpeer-review

11 Citations (Scopus)


We investigate the nonlinear mechanics of a bimetallic, optically absorbing SiN-Nb nanowire in the presence of incident laser light and a reflecting Si mirror. Situated in a standing wave of optical intensity and subject to photothermal forces, the nanowire undergoes self-induced oscillations at low incident light thresholds of <1 μW due to engineered strong temperature-position (T-z) coupling. Along with inducing self-oscillation, laser light causes large changes to the mechanical resonant frequency ω0 and equilibrium position z0 that cannot be neglected. We present experimental results and a theoretical model for the motion under laser illumination. In the model, we solve the governing nonlinear differential equations by perturbative means to show that self-oscillation amplitude is set by the competing effects of direct T-z coupling and 2ω0 parametric excitation due to T-ω0 coupling. We then study the linearized equations of motion to show that the optimal thermal time constant τ for photothermal feedback is τ → ∞ rather than the previously reported ω0 τ = 1. Lastly, we demonstrate photothermal quality factor (Q) enhancement of driven motion as a means to counteract air damping. Understanding photothermal effects on nano- and micromechanical devices, as well as nonlinear aspects of optics-based motion detection, can enable new device applications as oscillators or other electronic elements with smaller device footprints and less stringent ambient vacuum requirements.

Original languageEnglish
Pages (from-to)3995-4002
Number of pages8
JournalNano Letters
Issue number7
Publication statusPublished - 12 Jul 2017
MoE publication typeA1 Journal article-refereed


  • Nanomechanical systems
  • nonlinear dynamics
  • optomechanics
  • parametric feedback
  • photothermal force
  • self-oscillation


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