Versatile Optofluidic Solid-Core/Liquid-Cladding Waveguide Based on Evanescent Wave Excitation.

Area of Science:

• Optics and Photonics
• Microfluidics
• Biophotonics

Background:

• Evanescent wave excitation is crucial for sensitive optical detection.
• Microfluidic integration offers precise control over excitation and sample interaction.
• Traditional methods often suffer from background noise and limited signal-to-noise ratios.

Purpose of the Study:

• To design and demonstrate a novel solid-core/liquid-cladding (SL) waveguide system.
• To leverage evanescent wave excitation for enhanced fluorescence measurements.
• To explore applications in high-sensitivity detection and on-chip light sources.

Main Methods:

• Integrating an optical fiber into a microfluidic channel.
• Utilizing evanescent field coupling for excitation of cladding solution.
• Guiding pump beam via total internal reflection for uniform excitation.
• Performing fluorescence intensity measurements with varying dye concentrations and cladding refractive indices.

Main Results:

• Achieved peak intensity propagation loss as low as 0.1 dB/cm.
• Demonstrated good linearity between fluorescence intensity and dye concentration (<250 μM).
• Showcased a broadband, simultaneous light source using cascaded SL waveguide segments and fluorescence resonance energy transfer (FRET).

Conclusions:

• The SL waveguide offers robust, sensitive, and versatile platform for various applications.
• The system significantly reduces background fluorescence and enhances signal-to-noise ratio.
• Potential applications include low-concentration sample detection, on-chip light sources, and multiplexed parameter measurements.