High-frequency, resonant acousto-optic modulators fabricated in a MEMS foundry platform

We report the design and characterization of high frequency, resonant acousto-optic modulators (AOM) in a MEMS foundry process. The doubly-resonant cavity design, with short ($L{\sim}10.5\, {\mu}m$) acoustic and optical cavity lengths, allows us to measure acousto-optic modulation at GHz frequencies with high modulation efficiency. In contrast to traditional AOMs, these devices rely on the perturbation induced by the displacement of cavity boundaries, which can be significantly enhanced in a suspended geometry. This platform can serve as the building block for fast 2D spatial light modulators (SLM), low-cost integrated free space optical links and optically enhanced low-noise RF receivers.Comment: References and Figure 8 update

Light modulation in Silicon photonics by PZT actuated acoustic waves

Tailoring the interaction between light and sound has opened new possibilities in photonic integrated circuits (PICs) that ranges from achieving quantum control of light to high-speed information processing. However, the actuation of sound waves in Si PICs usually requires integration of a piezoelectric thin film. Lead Zirconate Titanate (PZT) is a promising material due to its strong piezoelectric and electromechanical coupling coefficient. Unfortunately, the traditional methods to grow PZT on Silicon are detrimental for photonic applications due to the presence of an optical lossy intermediate layer. In this work, we report integration of a high quality PZT thin film on a Silicon-on-insulator (SOI) photonic chip using an optically transparent buffer layer. We demonstrate acousto-optic modulation in Silicon waveguides with the PZT actuated acoustic waves. We fabricate inter digital transducers (IDTs) on the PZT film with a contact photo-lithography and electron-beam lithography to generate the acoustic waves in MHz and GHz range respectively. We obtain a V$_{\pi}$L $\sim$ 3.35 V$\cdot$cm at 576 MHz from a 350 nm thick gold (Au) IDT with 20 finger-pairs. After taking the effect of mass-loading and grating reflection into account, we measured a V$_{\pi}$L $\sim$ 3.60 V$\cdot$cm at 2 GHz from a 100 nm thick Aluminum (Al) IDT consisting of only 4 finger-pairs. Thus, without patterning the PZT film nor suspending the device, we obtained figures-of-merit comparable to state-of-the-art modulators based on SOI, making it a promising candidate for broadband and efficient acousto-optic modulator for future integration

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

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-of-magnitude 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-to-optical photon conversion, sensing and microwave signal processing.Comment: 26 pages, 5 figure

The 2019 surface acoustic waves roadmap

Today, surface acoustic waves (SAWs) and bulk acoustic waves are already two of the very few phononic technologies of industrial relevance and can been found in a myriad of devices employing these nanoscale earthquakes on a chip. Acoustic radio frequency filters, for instance, are integral parts of wireless devices. SAWs in particular find applications in life sciences and microfluidics for sensing and mixing of tiny amounts of liquids. In addition to this continuously growing number of applications, SAWs are ideally suited to probe and control elementary excitations in condensed matter at the limit of single quantum excitations. Even collective excitations, classical or quantum are nowadays coherently interfaced by SAWs. This wide, highly diverse, interdisciplinary and continuously expanding spectrum literally unites advanced sensing and manipulation applications. Remarkably, SAW technology is inherently multiscale and spans from single atomic or nanoscopic units up even to the millimeter scale. The aim of this Roadmap is to present a snapshot of the present state of surface acoustic wave science and technology in 2019 and provide an opinion on the challenges and opportunities that the future holds from a group of renown experts, covering the interdisciplinary key areas, ranging from fundamental quantum effects to practical applications of acoustic devices in life science

Feed-forward technique to measure S-parameters under jamming CW high power out-of-band signals

In recent years, high-power radio frequency (RF) devices have become increasingly common due in part, to the high-speed telecommunications industry. The evolution of mobile devices drives to the use of wireless applications which will require different work frequencies and therefore the implementation of new and miniaturized devices. Moreover, passive intermodulation requirements at high-power levels, power handling of transmitting filters, thermal stability behaviour of duplexers, interference blockers, etc. are some examples of the increasing interest in characterizing passive devices such when they are driven by high power signals. Nowadays, there exist devices that use the above-mentioned power requirements. For example, a radar protection circuit of jamming signals incorporating frequency-selective auto-limiting devices must keep the low-signal performance while dealing with high power signals. The high-power components used in these applications must be characterized for both linear and nonlinear operation. Therefore, complex calibration procedures must be done and the calibration standard must be able to handle the power without changing their parameters or alternatively, using previously characterized power standards. Feed-forward techniques have been shown very useful to measure passive intermodulation (PIM) without using narrowband filters. The objective in PIM measurements is cancelling the high-power tone before going into the spectrum analyzer. Since no filters are required, there are no restrictions between the separation of tones and the system is not-specific to a given narrowband bandwidth. This master thesis is focused in the study of the interference problem in high-power transmitted signals and out-of-band transmissions through the design of different feed-forward cancellation algorithms with the aim of measure and characterize high-power components as well as study the nonlinear behaviour caused by thermal effects of Bulk Acoustic Wave (BAW) resonators due to the use of high-power signals

Ferroelectric thin film acoustic devices with electrical multiband switching ability

Design principles of a new class of microwave thin film bulk acoustic resonators with multiband resonance frequency switching ability are presented. The theory of the excitation of acoustic eigenmodes in multilayer ferroelectric structures is considered, and the principle of selectivity for resonator with an arbitrary number of ferroelectric layers is formulated. A so called “criterion function” is suggested that allows to determine the conditions for effective excitation at one selected resonance mode with suppression of other modes. The proposed theoretical approach is verifiedusing thepreexisting experimental data published elsewhere. Finally, the possible application of the two ferroelectric layers structures for switchable microwave overtone resonators, binary and quadrature phase-shift keying modulators are discussed. These devices could play a pivotal role in the miniaturization of microwave front-end antenna circuits