Whispering gallery mode (WGM) glass bottle microresonators are potential highly sensitive structures for a variety of physical and bio-chemical sensing applications. In this paper, we experimentally demonstrate the practical use of glass bottle resonators as temperature sensors. The basic parameters, such as WGM resonance wavelengths, free spectral ranges, and Q factors, have been investigated by coupling light from a tapered fiber to the bottle structure. We show the spectral characteristics of the WGMs by choosing different bottle dimensions and taper diameters. For practical measurements, a robust 3D-printed package that includes the bottle resonator and the tapered fiber has been proposed. The packaged bottle has a central diameter Dc = 207 µm and a length L = 300 µm. Temperature sensing experiments were also performed. A linear response of the WGM shifts as a function of the temperature is confirmed. The fitted experimental data indicate a temperature sensitivity of 10.5 pm/K at λ ~ 1550 nm, resulting in a limit of detection of 0.06 K. These values can be compared with values reported for other WGM resonators. Additionally, bottle resonators are made with simple splicing methods and their assembly method can be easily defined due to large coupling tolerances.

No abstract

No abstract

In the last decades, coupling strategies of optical microresonators have been intensively explored to develop highly sensitive and label-free miniaturized biosensors. This work presents an innovative semi-automatic assembly approach for glass microbottles on a photonic integrated circuit (PIC) with single-mode waveguides. Microbottles are extraordinary whispering-gallery-mode (WGM) structures with additional axial confinement of the light along the bottle shape. A high dense spectrum of resonances varying along the bottle curvature is typically observed. To excite these resonances, the evanescent field of waveguides is used, as it provides direct evanescent interaction, integration of multiple structures and mass production. Initial coupling tests in air yielded a Q factor of 10 4 at 1550 nm by employing an active alignment setup and a customized gripping tool. Lateral coupling tolerances of Δx = ±50 μm and Δy = ±2 μm for a bottle diameter of 180 m were also found. An existing assembly machine including a visual system, alignment system, high precision glue dispenser and UV light was used for the identification, placement and fixation of microbottles. A highest Q factor of 10 5 was determined after the attachment of a microbottle. Similar results were obtained with bio-chemical modified samples. A laser cutting method was also applied for reducing the fiber length of the microbottle. In this way the hybrid PIC can be compatible with microfluidics. The dedicated assembly process is a promising tool to bring optical resonators into practical use for label-free biochemical sensing but also for other applications such as quantum sensing and communication.

No abstract