Geometry-induced fluorescence resonances in small lossy capillaries.

Area of Science:

• Optics and Photonics
• Spectroscopy
• Physical Chemistry

Background:

• Morphology-dependent resonances (MDRs), also known as whispering-gallery modes (WGMs), are typically observed in optical cavities exhibiting total internal reflection.
• These resonances are crucial for understanding light confinement and interaction with matter in various photonic devices.
• Previous studies have primarily focused on high-quality factor cavities where total internal reflection is a prerequisite.

Purpose of the Study:

• To experimentally demonstrate cavity-induced resonances in the absence of total internal reflection.
• To investigate the formation of whispering-gallery modes in a lossy, small-scale cavity.
• To explore the potential for generating optical resonances in unconventional cavity designs.

Main Methods:

• Experimental observation of fluorescence spectra from molecules within a small, lossy capillary.
• Utilizing a capillary zone electrophoresis setup to contain the sample.
• Analyzing the fluorescence spectrum for superimposed resonance peaks.

Main Results:

• Successful experimental demonstration of cavity-induced resonances without relying on total internal reflection.
• Observation of resonance peaks superimposed on a smooth fluorescence spectrum, indicating feedback.
• Identification of these resonances as morphology-dependent resonances or whispering-gallery modes.

Conclusions:

• Cavity-induced resonances can occur even with weak reflections, challenging the necessity of total internal reflection.
• Lossy, small-scale cavities like capillaries can support whispering-gallery modes.
• This work opens new avenues for utilizing resonance phenomena in micro- and nano-photonic systems.