Controlling phonons and photons at the wavelength scale: integrated photonics meets integrated phononics

Abstract

Radio-frequency communication systems have long used bulk-and surface-acoustic-wave devices supporting ultrasonic mechanical waves to manipulate and sense signals. These devices have greatly improved our ability to process microwaves by interfacing them to orders-ofmagnitude slower and lower loss mechanical fields. In parallel, long-distance communications have been dominated by low-loss infrared optical photons. As electrical signal processing and transmission approaches physical limits imposed by energy dissipation, optical links are now being actively considered for mobile and cloud technologies. Thus there is a strong driver for wavelength-scale mechanical wave or "phononic" circuitry fabricated by scalable semiconductor processes. With the advent of these circuits, new micro-and nanostructures that combine electrical, optical and mechanical elements have emerged. In these devices, such as optomechanical waveguides and resonators, optical photons and gigahertz phonons are ideally matched to one another as both have wavelengths on the order of micrometers. The development of phononic circuits has thus emerged as a vibrant field of research pursued for optical signal processing and sensing applications as well as emerging quantum technologies. In this review, we discuss the key physics and figures of merit underpinning this field. We also summarize the state of the art in nanoscale electro-and optomechanical systems with a focus on scalable platforms such as silicon. Finally, we give perspectives on what these new systems may bring and what challenges they face in the coming years. In particular, we believe hybrid electro-and optomechanical devices incorporating highly coherent and compact mechanical elements on a chip have significant untapped potential for electro-optic modulation, quantum microwave-tooptical photon conversion, sensing and microwave signal processing.

Photon and phonon spectral functions for continuum quantum optomechanics

“…For nanoscale waveguides we can take the typical physical numbers of ω 0 /(2π) ≈ 10 14 Hz, with the light group velocity of v g ≈ c/5 (acording to our results for a nanofiber made of silicon [5]). In figure (2) we plot the photon linear dispersion, ω k , as a function of ka, for the lowest photon branch. Here we consider a cylindrical waveguide of radius a = 250 nm and with the length of one centimeter.…”

“…Here we consider a cylindrical waveguide of radius a = 250 nm and with the length of one centimeter. Photons have relatively long lifetimes inside nanoscale waveguides [2]. The photon lifetimes can be considered by including damping rates, γ kµ , phenomenologically, where typical numbers for nanoscale waveguides are of about 10 4 −10 5 Hz, which can be extracted from experimental observations.…”

“…Phonon lifetimes of mechanical excitations are limited by structural and thermal disorders [2], and can be included phenomenologically through the damping rates, Γ qα . Typical numbers for phonon damping rates in silicon nanowires are in the range of 1 − 10 MHz, as observed in several experiments [2]. Inside nanoscale waveguides the photons and phonons are strongly interact due to electrostriction and radiation pressure.…”

Coherent Conversion Between Microwave and Optical Photons—An Overview of Physical Implementations

“…The figure of merit here is the energy-per-qubit, the quantum equivalent of the energy-per-bit-the energy associated with each transmitted data bit. [26,27] Finally, quantum systems rapidly lose information to their environment due to decoherence. The device must therefore have enough bandwidth for sufficient information to be transmitted before it is lost-the best decoherence times for superconducting qubits approach 0.1 ms, [28] corresponding to a bandwidth of 10 kHz.…”

ARRAW: anti-resonant reflecting acoustic waveguides

“…A number of designs have been put forward to address this challenge [1][2][3][4]. In some, the waveguides are suspended in air by either sparsely positioned [5][6][7] or specifically engineered supporting structures [8].…”