A NEW BROADBAND CAVITY ENHANCED FREQUENCY COMB SPECTROSCOPY TECHNIQUE USING GHz VERNIER FILTERING.

AbstractCavity optomechanics has recently emerged as a new paradigm enabling the manipulation of mechanical motion via optical fields tightly confined in deformable cavities. When driving an optomechanical (OM) crystal cavity with a laser blue-detuned with respect to the optical resonance, the mechanical motion is amplified, ultimately resulting in phonon lasing at MHz and even GHz frequencies. In this work, we show that a silicon OM crystal cavity performs as an OM microwave oscillator when pumped above the threshold for self-sustained OM oscillations. To this end, we use an OM cavity designed to have a breathing-like mechanical mode at 3.897 GHz in a full phononic bandgap. Our measurements show that the first harmonic of the detected signal displays a phase noise of ≈−100 dBc/Hz at 100 kHz. Stronger blue-detuned driving leads eventually to the formation of an OM frequency comb, whose lines are spaced by the mechanical frequency. We also measure the phase noise for higher-order harmonics and show that, unlike in Brillouin oscillators, the noise is increased as corresponding to classical harmonic mixing. Finally, we present real-time measurements of the comb waveform and show that it can be fitted to a theoretical model recently presented. Our results suggest that silicon OM cavities could be relevant processing elements in microwave photonics and optical RF processing, in particular in disciplines requiring low weight, compactness and fiber interconnection.

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Simple method for mid-infrared optical frequency comb generation with dynamic offset frequency tuning

APL Photonics ◽

10.1063/5.0038496 ◽

2021 ◽

Vol 6 (2) ◽

pp. 026103

Author(s):

Mikhail Roiz ◽

Krishna Kumar ◽

Juho Karhu ◽

Markku Vainio

Keyword(s):

Frequency Tuning ◽

Frequency Comb ◽

Optical Frequency Comb ◽

Optical Frequency ◽

Simple Method ◽

Mid Infrared ◽

Comb Generation ◽

Offset Frequency

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Acoustic cavities in 2D heterostructures

Nature Communications ◽

10.1038/s41467-021-23359-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Maxim K. Zalalutdinov ◽

Jeremy T. Robinson ◽

Jose J. Fonseca ◽

Samuel W. LaGasse ◽

Tribhuwan Pandey ◽

...

Keyword(s):

Sound Propagation ◽

Phonon Scattering ◽

Frequency Comb ◽

Material Interfaces ◽

Low Frequencies ◽

Strongly Coupled ◽

Propagation Analysis ◽

Acoustic Cavities ◽

Ab Initio Approach ◽

Spatiotemporal Response

AbstractTwo-dimensional (2D) materials offer unique opportunities in engineering the ultrafast spatiotemporal response of composite nanomechanical structures. In this work, we report on high frequency, high quality factor (Q) 2D acoustic cavities operating in the 50–600 GHz frequency (f) range with f × Q up to 1 × 1014. Monolayer steps and material interfaces expand cavity functionality, as demonstrated by building adjacent cavities that are isolated or strongly-coupled, as well as a frequency comb generator in MoS2/h-BN systems. Energy dissipation measurements in 2D cavities are compared with attenuation derived from phonon-phonon scattering rates calculated using a fully microscopic ab initio approach. Phonon lifetime calculations extended to low frequencies (<1 THz) and combined with sound propagation analysis in ultrathin plates provide a framework for designing acoustic cavities that approach their fundamental performance limit. These results provide a pathway for developing platforms employing phonon-based signal processing and for exploring the quantum nature of phonons.

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