Engineering Multiple GHz Mechanical Modes in Optomechanical Crystal Cavities (original) (raw)

A one-dimensional optomechanical crystal with a complete phononic band gap

Nature Communications, 2014

Recent years have witnessed the boom of cavity optomechanics, which exploits the confinement and coupling of optical waves and mechanical vibrations at the nanoscale 1,2 . Amongst the different physical implementations 3 , optomechanical (OM) crystals 4,5 built on semiconductor slabs are particularly interesting since they enable the integration and manipulation of multiple OM elements in a single chip and provide GHz phonons suitable for coherent phonon manipulation . Different demonstrations of coupling of infrared photons and GHz phonons in cavities created by inserting defects on OM crystals have been performed . However, the considered structures do not show a complete phononic bandgap at the frequencies of interest, which in principle should allow longer dephasing time, since acoustic leakage is minimized. In this work we demonstrate the excitation of acoustic modes in a 1D OM crystal properly designed to display a full phononic bandgap for acoustic modes at about 4 GHz. The confined phonons have an OM coupling ranging from the KHz to the MHz range with contributions from moving interfaces and the photoelastic effect that add constructively for many of them. The modes inside the complete bandgap are designed to have mechanical Q factors above 10 8 and invariant to fabrication imperfections, what would allow several coherent phonon manipulations at moderate cryogenic temperatures. At room temperature and atmospheric pressure, though, they present experimentally Q factors around 2000 limited by extrinsic damping and/or a combination of intrinsic phonon scattering mechanisms, like thermo-elastic decay or Akhieser. Interestingly, we also report the excitation of acoustic modes up to 8 GHz, the highest frequency reported so far.

Multimode circuit optomechanics near the quantum limit

Nature Communications, 2012

The coupling of distinct systems underlies nearly all physical phenomena. A basic instance is that of interacting harmonic oscillators, giving rise to, for example, the phonon eigenmodes in a lattice. Of particular importance are the interactions in hybrid quantum systems, which can combine the benefits of each part in quantum technologies. Here we investigate a hybrid optomechanical system having three degrees of freedom, consisting of a microwave cavity and two micromechanical beams with closely spaced frequencies around 32 MHz and no direct interaction. We record the first evidence of tripartite optomechanical mixing, implying that the eigenmodes are combinations of one photonic and two phononic modes. We identify an asymmetric dark mode having a long lifetime. Simultaneously, we operate the nearly macroscopic mechanical modes close to the motional quantum ground state, down to 1.8 thermal quanta, achieved by back-action cooling. These results constitute an important advance towards engineering of entangled motional states.

Si3N4 optomechanical crystals in the resolved-sideband regime

Applied Physics Letters, 2014

We demonstrate sideband-resolved Si3N4 optomechanical crystals supporting 10 5 quality factor optical modes at 980 nm, coupled to ≈ 4 GHz frequency mechanical modes with quality factors of ≈ 3000. Optomechanical electromagnetically induced transparency and absorption are observed at room temperature and in atmosphere with intracavity photon numbers of the order of 10 4 .

Two-dimensional optomechanical crystal resonator in gallium arsenide

arXiv (Cornell University), 2023

In the field of quantum computation and communication there is a compelling need for quantumcoherent frequency conversion between microwave electronics and infra-red optics. A promising platform for this is an optomechanical crystal resonator that uses simultaneous photonic and phononic crystals to create a co-localized cavity coupling an electromagnetic mode to an acoustic mode, which then via electromechanical interactions can undergo direct transduction to electronics. The majority of work in this area has been on one-dimensional nanobeam resonators which provide strong optomechanical couplings but, due to their geometry, suffer from an inability to dissipate heat produced by the laser pumping required for operation. Recently, a quasi-two-dimensional optomechanical crystal cavity was developed in silicon exhibiting similarly strong coupling with better thermalization, but at a mechanical frequency above optimal qubit operating frequencies. Here we adapt this design to gallium arsenide, a natural thin-film single-crystal piezoelectric that can incorporate electromechanical interactions, obtaining a mechanical resonant mode at fm ≈ 4.5 GHz ideal for superconducting qubits, and demonstrating optomechanical coupling gom/(2 π) ≈ 650 kHz.

Cavity optomechanics with ultrahigh-Q crystalline microresonators

Physical Review A, 2010

We present the first observation of optomechanical coupling in ultra-high Q crystalline whisperinggallery-mode (WGM) resonators. The high purity of the crystalline material enables optical quality factors in excess of 10 10 and finesse exceeding 10 6 . Simultaneously, mechanical quality factors greater than 10 5 are obtained, still limited by clamping losses. Compared to previously demonstrated cylindrical resonators, the effective mass of the mechanical modes can be dramatically reduced by the fabrication of CaF2 microdisc resonators. Optical displacement monitoring at the 10 −18 m/ √ Hzlevel reveals mechanical radial modes at frequencies up to 20 MHz, corresponding to unprecedented sideband factors (> 100). Together with the weak intrinsic mechanical damping in crystalline materials, such high sindeband factors render crystalline WGM micro-resonators promising for backaction evading measurements, resolved sideband cooling or optomechanical normal mode splitting. Moreover, these resonators can operate in a regime where optomechanical Brillouin lasing can become accessible. PACS numbers: 42.65.Sf, 42.50.Wk

Position-Squared Coupling in a Tunable Photonic Crystal Optomechanical Cavity

Physical Review X, 2015

We present the design, fabrication, and characterization of a planar silicon photonic crystal cavity in which large position-squared optomechanical coupling is realized. The device consists of a double-slotted photonic crystal structure in which motion of a central beam mode couples to two high-Q optical modes localized around each slot. Electrostatic tuning of the structure is used to controllably hybridize the optical modes into supermodes that couple in a quadratic fashion to the motion of the beam. From independent measurements of the anticrossing of the optical modes and of the dynamic optical spring effect, a positionsquared vacuum coupling rate as large asg 0 =2π ¼ 245 Hz is inferred between the optical supermodes and the fundamental in-plane mechanical resonance of the structure at ω m =2π ¼ 8.7 MHz, which in displacement units corresponds to a coupling coefficient of g 0 =2π ¼ 1 THz=nm 2. For larger supermode splittings, selective excitation of the individual optical supermodes is used to demonstrate optical trapping of the mechanical resonator with measuredg 0 =2π ¼ 46 Hz.

Hybrid optomechanics for Quantum Technologies

Quantum Measurements and Quantum Metrology, 2014

We review the physics of hybrid optomechanical systems consisting of a mechanical oscillator interacting with both a radiation mode and an additional matterlike system. We concentrate on the cases embodied by either a single or a multi-atom system (a Bose-Einstein condensate, in particular) and discuss a wide range of physical effects, from passive mechanical cooling to the set-up of multipartite entanglement, from optomechanical non-locality to the achievement of non-classical states of a single mechanical mode. The reviewed material showcases the viability of hybridised cavity optomechanical systems as basic building blocks for quantum communication networks and quantum state-engineering devices, possibly empowered by the use of quantum and optimal control techniques. The results that we discuss are instrumental to the promotion of hybrid optomechanical devices as promising experimental platforms for the study of nonclassicality at the genuine mesoscopic level.

Quantum correlations in optomechanical crystals

Physical Review A, 2019

The field of optomechanics provides us with several examples of quantum photon-phonon interface. In this paper, we theoretically investigate the generation and manipulation of quantum correlations in a microfabricated optomechanical array. We consider a system consisting of localized photonic and phononic modes interacting locally via radiation pressure at each lattice site with the possibility of hopping of photons and phonons between neighboring sites. We show that such an interaction can correlate various modes of a driven coupled optomechanical array with well-chosen system parameters. Moreover, in the linearized regime of Gaussian fluctuations, the quantum correlations not only survive in the presence of thermal noise, but may also be generated thermally. We find that these optomechanical arrays provide a suitable platform for quantum simulation of various many-body systems.

Design of a quasi-2D photonic crystal optomechanical cavity with tunable, large x^2-coupling

2016

We present the optical and mechanical design of a mechanically compliant quasi-two-dimensional photonic crystal cavity formed from thin-film silicon in which a pair of linear nanoscale slots are used to create two coupled high-Q optical resonances. The optical cavity supermodes, whose frequencies are designed to lie in the 1500 nm wavelength band, are shown to interact strongly with mechanical resonances of the structure whose frequencies range from a few MHz to a few GHz. Depending upon the symmetry of the mechanical modes and the symmetry of the slot sizes, we show that the optomechanical coupling between the optical supermodes can be either linear or quadratic in the mechanical displacement amplitude. Tuning of the nanoscale slot size is also shown to adjust the magnitude and sign of the cavity supermode splitting 2J, enabling near-resonant motional scattering between the two optical supermodes and greatly enhancing the x^2-coupling strength. Specifically, for the fundamental fle...