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Register a new userHybrid confinement of optical and mechanical modes in a bullseye optomechanical resonator
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Added by
Thiago P. Mayer Alegre
Publication date
2016
fields
Physics
and research's language is
English
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Optomechanical cavities have proven to be an exceptional tool to explore fundamental and technological aspects of the interaction between mechanical and optical waves. Such interactions strongly benefit from cavities with large optomechanical coupling, high mechanical and optical quality factors, and mechanical frequencies larger than the optical mode linewidth, the so called resolved sideband limit. Here we demonstrate a novel optomechanical cavity based on a disk with a radial mechanical bandgap. This design confines light and mechanical waves through distinct physical mechanisms which allows for independent control of the mechanical and optical properties. Our device design is not limited by unique material properties and could be easily adapted to allow large optomechanical coupling and high mechanical quality factors with other promising materials. Finally, our demonstration is based on devices fabricated on a commercial silicon photonics facility, demonstrating that our approach can be easily scalable.
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The integration of optomechanics and optoelectronics in a single device opens new possibilities for developing information technologies and exploring fundamental phenomena. Gallium arsenide (GaAs) is a well-known material that can bridge the gap between the functionalities of optomechanical devices and optical gain media. Here, we experimentally demonstrate a high-frequency GaAs optomechanical resonator with a ring-type bullseye geometry that is unprecedented in this platform. We measured mechanical modes up to 3.4 GHz with quality factors of 4000 (at 77 K) and optomechanical coupling rates up to 39 kHz at telecom wavelengths. Moreover, we investigated the material symmetry break due to elastic anisotropy and its impact on the mechanical mode spectrum. Finally, we assessed the temperature dependence of the mechanical losses and demonstrated the efficiency and anisotropy resilience of the bullseye anchor loss suppression, indicating that lower temperature operation may allow mechanical quality factors over $10^4$. Such characteristics are valuable for active optomechanics, coherent microwave-to-optics conversion via piezo-mechanics and other implementations of high-frequency oscillators in III-V materials.
We theoretically study a strongly-driven optomechanical system which consists of a passive optical cavity and an active mechanical resonator. When the optomechanical coupling strength is varied, phase transitions, which are similar those observed in $mathcal{PT}$-symmetric systems, are observed. We show that the optical transmission can be controlled by changing the gain of the mechanical resonator and loss of the optical cavity mode. Especially, we find that: (i) for balanced gain and loss, optical amplification and absorption can be tuned by changing the optomechanical coupling strength through a control field; (ii) for unbalanced gain and loss, even with a tiny mechanical gain, both optomechanically-induced transparency and anomalous dispersion can be observed around a critical point, which exhibits an ultra-long group delay. The time delay $tau$ can be optimized by regulating the optomechanical coupling strength through the control field and improved up to several orders of magnitude ($tausim2$ $mathrm{ms}$) compared to that of conventional optomechanical systems ($tausim1$ $mumathrm{s}$). The presence of mechanical gain makes the group delay more robust to environmental perturbations. Our proposal provides a powerful platform to control light transport using a $mathcal{PT}$-symmetric-like optomechanical system.
Robust control and stabilization of optical frequency combs enables an extraordinary range of scientific and technological applications, including frequency metrology at extreme levels of precision, novel spectroscopy of quantum gases and of molecules from visible wavelengths to the far infrared, searches for exoplanets, and photonic waveform synthesis. Here we report on the stabilization of a microresonator-based optical comb (microcomb) by way of mechanical actuation. This represents an important step in the development of microcomb technology, which offers a pathway toward fully-integrated comb systems. Residual fluctuations of our 32.6 GHz microcomb line spacing reach a record stability level of $5times10^{-15}$ for 1 s averaging, thereby highlighting the potential of microcombs to support modern optical frequency standards. Furthermore, measurements of the line spacing with respect to an independent frequency reference reveal the effective stabilization of different spectral slices of the comb with a $<$0.5 mHz variation among 140 comb lines spanning 4.5 THz. These experiments were performed with newly-developed microrod resonators, which were fabricated using a CO$_2$-laser-machining technique.
We propose a plasmonic ellipse resonator possessing hybrid modes based on metal-insulator-metal (MIM) waveguide system. Specially, this nanocavity has hybrid characteristic of rectangle and disk resonator, therefore supporting both Fabry-Perot modes (FPMs) and whispering-gallery modes (WGMs). Besides, by changing the length of major and minor radius of the ellipse, the resonant wavelengths of FPMs and WGMs can be independently tuned and close to each other, thus constructing a plasmon-induced transparency (PIT) - like spectrum profile. Benefitting from this, a dual-band slow light is achieved with one single resonator. Furthermore, this component can also act as a multi-band color filter and refractive index sensor. We believe such multi-mode resonator with ultra-small footprint will play an important role in more compact on-chip optical circuits in the future.
This note describes the analytical derivation of the response of bullseye detectors to optical beats between higher-order spatial modes of the Laguerre-Gauss form, and subsequently the Hermite-Gauss form. Also included is a comparison with numerically calculated beat coefficients, and a simple example of the use of the resulting beat coefficients in simulating a mode mismatch sensor for a Fabry-Perot cavity.
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