Thermometric absorption spectroscopy through active locking of microbubble resonators

We implemented a Microbubble Resonator (MBRs) as an opto-thermal transducer to reconstruct the absorption spectrum of a nanoparticle suspension through its temperature increase. The experimental configuration features the MBR as both the vial containing the suspension and the optical transducer, allowing for a sensitive ultra-compact system with a straightforward microfluidic integration. With respect to a previous publication, the active lock of the MBR resonance produced an order-of-magnitude improvement in the system performance and a smooth absorption reconstruction. Additionally, since the detection process is temperature-based, the measurement is intrinsically insensitive towards scattering spectrum, both of the particles and of the host liquid. These features make the MBR system an interesting candidate for the characterisation of extremely small samples in the context of medical diagnosis from whole biological samples, quality controls for food safety or chemical production processes, and, in general, for the measurement of absorption in opaque mediums

Microbubble whispering gallery mode resonator as an all-optical platform for the characterisation of photoacoustics contrast agents

This article presents a microbubble resonator (MBR) as an alloptical ultrasound transducer specialized for the characterisation of photoacoustics (PA) contrast agents. In the presented proof-of-concept experiment, a well-known contrast agent (gold nanorods, GNRs) was placed within the MBR and acoustic detection was achieved by monitoring an MBR optical resonance, exploiting the MBR mechanical resonances to enhance the transduction mechanism. The read-out signal from the MBR was validated through a numerical simulation and through the reconstruction of the GNRs photostability trend, proving the feasibility of the characterisation. This work sets the stage for the application of the MBR system to a specific task, taking advantage of its promising features: sensitive PA detection, extremely small volume, ease of integration in a microfluidic circuit, absence of acoustic matching material and scalability

Nonlinear Optics in Microspherical Resonators

Nonlinear frequency generation requires high intensity density which is usually achieved with pulsed laser sources, anomalous dispersion, high nonlinear coefficients or long interaction lengths. Whispering gallery mode microresonators (WGMRs) are photonic devices that enhance nonlinear interactions and can be exploited for continuous wave (CW) nonlinear frequency conversion, due to their capability of confine light for long time periods in a very small volume, even though in the normal dispersion regime. All signals must be resonant with the cavity. Here, we present a review of nonlinear optical processes in glass microspherical cavities, hollow and solid

Er3+ doped tellurite whispering gallery mode microlasers in 1.5 μm–1.61 μm wavelength region generated by 0.98 μm and 1.48 μm pump lasers

In this paper, we demonstrate Er3+ doped tellurite single and multi-mode microlasers in 1.5 μm–1.6 μm wavelength range fabricated via the plasma torch method. It is a simple and cost-effective method to produce microspheres with diameter ranges from 11 to 88 μm. Single mode laser output were observed with 0.98 μm and 1.48 μm pump, respectively. In addition, the quality factor of the fabricated microsphere is measured

Coupling analysis of high Q resonators in add-drop configuration through cavity ringdown spectroscopy

International audienceAn original method able to fully characterize high-Q resonators in an add-drop configuration has been implemented. The method is based on the study of two cavity ringdown (CRD) signals, which are produced at the transmission and drop ports by wavelength sweeping a resonance in a time interval comparable with the photon cavity lifetime. All the resonator parameters can be assessed with a single set of simultaneous measurements. We first developed a model describing the two CRD output signals and a fitting program able to deduce the key parameters from the measured profiles. We successfully validated the model with an experiment based on a fiber ring resonator of known characteristics. Finally, we characterized a high-Q, home-made, MgF2 whispering gallery mode disk resonator in the add-drop configuration, assessing its intrinsic and coupling parameters

Rare earth-doped glass whispering gallery mode micro-lasers

International audienceWe review the works performed on whispering gallery mode (WGM) micro-optical resonators made in rare-earth (RE) doped glasses for implementing low threshold and narrow line coherent sources. These types of micro-lasers, because of their small size and ease of fabrication can be a useful tool for the characterization of laser glasses and have several applications, especially as sensors