Microbubble resonators for scattering-free absorption spectroscopy of nanoparticles

Active Control of Plasmonic-Photonic Interactions in a Microbubble Cavity

Active control of light-matter interactions using nanophotonic structures is critical for new modalities for solar energy production, cavity quantum electrodynamics (QED), and sensing, particularly at the single-particle level, where it underpins the creation of tunable nanophotonic networks. Coupled plasmonic-photonic systems show great promise toward these goals because of their subwavelength spatial confinement and ultrahigh-quality factors inherited from their respective components. Here, we present a microfluidic approach using microbubble whispering-gallery mode cavities to actively control plasmonic-photonic interactions at the single-particle level. By changing the solvent in the interior of the microbubble, control can be exerted on the interior dielectric constant and, thus, on the spatial overlap between the photonic and plasmonic modes. Qualitative agreement between experiment and simulation reveals the competing roles mode overlap and mode volume play in altering coupling strengths.

The potential of microbubbles as a cancer eradication theranostic agent

Microbubbles are a new kind of delivery system that may be used to treat a variety of illnesses, including cancer. Microbubble is a non-invasive technology that uses microscopic gas-filled colloidal particle bubbles with a size range of less than 100 micrometres. This unique carrier has been used in a variety of applications in the last decade, ranging from basic targeting to ultrasound-mediated drug delivery. The oxygen in the microbubble lasts longer in the water. The drug release mechanism is highly regulated, since it releases the medication only in the appropriate areas, increasing the local impact while reducing drug toxicity. This carrier is exceptional in cancer medication delivery because of its sustained stability, encapsulation efficiency, and drug targeting. In this paper, we provide a comprehensive analysis of microbubble technology, including its manufacturing techniques and use in cancer medication delivery.

Optical Whispering-Gallery-Mode Microbubble Sensors

Whispering-gallery-mode (WGM) microbubble resonators are ideal optical sensors due to their high quality factor, small mode volume, high optical energy density, and geometry/design/structure (i.e., hollow microfluidic channels). When used in combination with microfluidic technologies, WGM microbubble resonators can be applied in chemical and biological sensing due to strong light–matter interactions. The detection of ultra-low concentrations over a large dynamic range is possible due to their high sensitivity, which has significance for environmental monitoring and applications in life-science. Furthermore, WGM microbubble resonators have also been widely used for physical sensing, such as to detect changes in temperature, stress, pressure, flow rate, magnetic field and ultrasound. In this article, we systematically review and summarize the sensing mechanisms, fabrication and packing methods, and various applications of optofluidic WGM microbubble resonators. The challenges of rapid production and practical applications of WGM microbubble resonators are also discussed.

Cascade Brillouin Lasing in a Tellurite-Glass Microsphere Resonator with Whispering Gallery Modes

Brillouin microlasers based on microresonators with whispering gallery modes (WGMs) are in high demand for different applications including sensing and biosensing. We fabricated a microsphere resonator with WGMs from a synthesized high-quality tellurite glass with record high Q-factors for tellurite microresonators (Q ≥ 2.5 × 10⁷), a high Brillouin gain coefficient (compared to standard materials, e.g., silica glasses), and a Brillouin frequency shift of 9 ± 0.5 GHz. The high density of excited resonance modes and high loaded Q-factors allowed us to achieve experimentally cascade Stokes-Brillouin lasing up to the 4th order inclusive. The experimental results are supported by the results of the theoretical analysis. We also theoretically obtained the dependences of the output Brillouin powers on the pump power and found the pump-power thresholds for the first five Brillouin orders at different values of pump frequency detuning and Q-factors, and showed a significant effect of these parameters on the processes under consideration.