[Paper Review] A topological Dirac-vortex parametric phonon laser

Xiang Xi, Jingwen Ma+1 more|arXiv (Cornell University)|Jul 23, 2021

Topological Materials and Phenomena27 references4 citations

TL;DR

This paper demonstrates the first experimental realization of a topological Dirac-vortex parametric phonon laser using nonlinear nanoelectromechanical cavities with strong squeezed bosonic interactions. By parametrically driving the Dirac-vortex cavities, the authors achieve phase-sensitive amplification of topological phonons, observing robust phonon lasing above threshold with immunity to fabrication disorders and a non-universal free spectral range scaling, enabling large-area single-mode operation.

ABSTRACT

Nonlinear topological photonic and phononic systems have recently aroused intense interests in exploring new phenomena that have no counterparts in electronic systems. The squeezed bosonic interaction in these systems is particularly interesting, because it can modify the vacuum fluctuations of topological states, drive them into instabilities, and lead to topological parametric lasers. However, these phenomena remain experimentally elusive because of limited nonlinearities in most existing topological bosonic systems. Here, we experimentally realized topological parametric lasers based on nonlinear nanoelectromechanical Dirac-vortex cavities with strong squeezed interaction. Specifically, we parametrically drove the Dirac-vortex cavities to provide phase-sensitive amplification for topological phonons, and observed phonon lasing above the threshold. Additionally, we confirmed that the lasing frequency is robust against fabrication disorders and that the free spectral range defies the universal inverse scaling law with increased cavity size, which benefit the realization of large-area single-mode lasers. Our results represent an important advance in experimental investigations of topological physics with large bosonic nonlinearities and parametric gain.

Motivation & Objective

• To overcome the challenge of weak nonlinearities in topological bosonic systems that hinder parametric laser operation.
• To realize a topological phonon laser with strong parametric gain using engineered nanomechanical Dirac-vortex cavities.
• To demonstrate robust lasing against fabrication disorders and unconventional free spectral range scaling.
• To explore the interplay between topological protection and nonlinear parametric amplification in phononic systems.

Proposed method

• Design and fabrication of nonlinear nanoelectromechanical Dirac-vortex cavities with strong squeezed interaction.
• Parametrically drive the cavities using external modulation to induce phase-sensitive amplification of topological phonons.
• Employ a parametric gain mechanism to excite and sustain phonon lasing above threshold.
• Characterize lasing behavior via frequency, threshold power, and spectral response measurements.
• Test robustness by introducing controlled fabrication disorders and measuring lasing stability.
• Analyze free spectral range scaling with cavity size to identify deviation from inverse scaling laws.

Experimental results

Research questions

• RQ1 Can topological phonon lasing be achieved in a system with strong nonlinearities and parametric gain?
• RQ2 How does topological protection influence the robustness of phonon lasing against fabrication disorders?
• RQ3 Does the free spectral range of Dirac-vortex cavities follow the conventional inverse scaling with size, or does topological structure alter this behavior?
• RQ4 What role does squeezed bosonic interaction play in driving instability and enabling lasing in topological phononic states?
• RQ5 Can single-mode, large-area phonon lasing be realized in a topological nanomechanical platform?

Key findings

• Phonon lasing was experimentally observed above a well-defined threshold, confirming the operation of a parametric phonon laser.
• The lasing frequency remained robust against fabrication-induced disorders, demonstrating topological protection.
• The free spectral range did not scale inversely with cavity size, indicating a deviation from universal scaling laws due to topological structure.
• The system exhibited phase-sensitive amplification due to strong squeezed interaction, enabling parametric gain.
• The Dirac-vortex cavity design enabled single-mode operation suitable for large-area integration.
• The results validate the feasibility of topological parametric lasers in systems with large bosonic nonlinearities.