Al₂O₃:Yb³⁺ integrated microdisk laser label-free biosensor.

Area of Science:

• Photonics and Optical Engineering
• Biomedical Sensing Technologies
• Materials Science

Background:

• Whispering gallery mode (WGM) resonator lasers promise ultra-low limits of detection for biosensing.
• Current WGM laser configurations for biosensing often lack robustness and are complex.
• Overcoming these limitations is crucial for practical applications.

Purpose of the Study:

• To demonstrate a robust and integrated microdisk laser for biosensing applications.
• To utilize a material with low optical loss and emission outside water's absorption band.
• To achieve sensitive detection of biomarkers in biological fluids.

Main Methods:

• Fabrication of an integrated microdisk laser using Al2O3 doped with Yb3+.
• Achieving single-mode laser emission at 1024 nm with a narrow linewidth (250 kHz) in water.
• Experimental demonstration of protein detection using the microdisk laser.

Main Results:

• Single-mode laser emission was successfully obtained at 1024 nm, even when the microdisk cavity was submerged in water.
• The material (Al2O3:Yb3+) exhibited low optical losses and emission outside the water absorption band.
• A limit of detection of 300 pM (3.6 ng/ml) for the protein rhS100A4 in urine was achieved.

Conclusions:

• The integrated microdisk laser demonstrates a robust and sensitive platform for biosensing.
• This technology shows significant potential for real-world diagnostic applications.
• The developed device overcomes previous limitations in WGM laser biosensor complexity and robustness.