Observation of thermal acoustic modes of a droplet coupled to an optomechanical sensor

The bulk acoustic modes of liquid droplets, well understood from a theoretical perspective, have rarely been observed experimentally. Here, we report the direct observation of acoustic vibrational modes in a picoliter-scale droplet, extending up to ~ 40 MHz. This was achieved by coupling the droplet to an ultra-sensitive optomechanical sensor, which operates in a thermal-noise limited regime and with a substantial contribution from acoustic noise in the ambient medium. The droplet vibrational modes manifest as Fano resonances in the thermal noise spectrum of the sensor. This is amongst the few reported observations of droplet acoustic modes, and of Fano interactions in a coupled mechanical oscillator system driven only by thermal Brownian motion.Comment: 11 pages, 3 figure

Ultrasonic spectroscopy of sessile droplets coupled to optomechanical sensors

We describe a system for interrogating the acoustic properties of sub-nanoliter liquid samples within an open microfluidics platform. Sessile droplets were deposited onto integrated optomechanical sensors, which possess ambient-medium-noise-limited sensitivity and can thus passively sense the thermally driven acoustic spectrum of the droplets. The droplet acoustic breathing modes manifest as resonant features in the thermomechanical noise spectrum of the sensor, in some cases hybridized with the sensor's own vibrational modes. Excellent agreement is found between experimental observations and theoretical predictions, over the entire ~ 0 - 40 MHz operating range of our sensors. With suitable control over droplet size and morphology, this technique has the potential for precision acoustic sensing of small-volume biological and chemical samples

On-Chip High-Finesse Fabry-Perot Microcavities for Optical Sensing and Quantum Information

For applications in sensing and cavity-based quantum computing and metrology, open-access Fabry-Perot cavities—with an air or vacuum gap between a pair of high reflectance mirrors—offer important advantages compared to other types of microcavities. For example, they are inherently tunable using MEMS-based actuation strategies, and they enable atomic emitters or target analytes to be located at high field regions of the optical mode. Integration of curved-mirror Fabry-Perot cavities on chips containing electronic, optoelectronic, and optomechanical elements is a topic of emerging importance. Micro-fabrication techniques can be used to create mirrors with small radius-of-curvature, which is a prerequisite for cavities to support stable, small-volume modes. We review recent progress towards chip-based implementation of such cavities, and highlight their potential to address applications in sensing and cavity quantum electrodynamics

All-Optical, Air-Coupled Ultrasonic Detection of Low-Pressure Gas Leaks and Observation of Jet Tones in the MHz Range

We used an ultrasensitive, broadband optomechanical ultrasound sensor to study the acoustic signals produced by pressurized nitrogen escaping from a variety of small syringes. Harmonically related jet tones extending into the MHz region were observed for a certain range of flow (i.e., Reynolds number), which is in qualitative agreement with historical studies on gas jets emitted from pipes and orifices of much larger dimensions. For higher turbulent flow rates, we observed broadband ultrasonic emission in the ~0–5 MHz range, which was likely limited on the upper end due to attenuation in air. These observations are made possible by the broadband, ultrasensitive response (for air-coupled ultrasound) of our optomechanical devices. Aside from being of theoretical interest, our results could have practical implications for the non-contact monitoring and detection of early-stage leaks in pressured fluid systems

Design and fabrication of a planar PDMS transmission grating microspectrometer

We describe the monolithic integration of microfluidic channels, optical waveguides, a collimating lens and a curved focusing transmission grating in a single PDMS-based microsystem. All optical and fluidic components of the device were simultaneously formed in a single layer of high refractive index (n 3c1.43) PDMS by soft lithography. Outer layers of lower-index (n 3c1.41) PDMS were subsequently added to provide optical and fluidic confinement. Here, we focus on the design and characterization of the microspectrometer part, which employs a novel self-focusing strategy based on cylindrical facets, and exhibits resolution <10 nm in the visible wavelength range. The dispersive behavior of the grating was analyzed both experimentally and using numerical simulations, and the results are in good agreement with simplified analytical predictions. \ua9 2013 Optical Society of America.Peer reviewed: YesNRC publication: Ye

Supplementary document for Enhanced emission from hBN in sputtered microcavities - 6444461.pdf

Additional fabrication, characterization, and simulatio

Oxide Nanomaterials: Synthetic Developments, Mechanistic Studies, and Technological Innovations

Oxide nanomaterials are indispensable for nanotechnological innovations, because they combine an infinite variety of structural motifs and properties with manifold morphological features. Given that new oxide materials are almost reported on a daily basis, considerable synthetic and technological work remains to be done to fully exploit this ever increasing family of compounds for innovative nano-applications. This calls for reliable and scalable preparative approaches to oxide nanomaterials and their development remains a challenge for many complex nanostructured oxides. Oxide nanomaterials with special physicochemical features and unusual morphologies are still difficult to access by classic synthetic pathways. The limitless options for creating nano-oxide building blocks open up new technological perspectives with the potential to revolutionize areas ranging from data processing to biocatalysis. Oxide nanotechnology of the 21st century thus needs a strong interplay of preparative creativity, analytical skills, and new ideas for synergistic implementations