Ultralow-threshold continuous-wave lasing assisted by a metallic optofluidic cavity exploiting continuous pump.

Area of Science:

• Optofluidics
• Photonics
• Materials Science

Background:

• Optofluidic resonant cavities are crucial for developing advanced photonic devices.
• Achieving continuous-wave lasing with ultralow thresholds remains a significant challenge in photonics.
• Symmetrical metal-cladding waveguides offer unique properties for light confinement and interaction.

Purpose of the Study:

• To demonstrate ultralow-threshold continuous-wave lasing in a metallic optofluidic resonant cavity.
• To investigate the role of high quality factor (Q) and spontaneous emission coupling factor (β) in enhancing lasing efficiency.
• To verify the applicability of the proposed concept using Rhodamine 6G and methylene blue as gain media.

Main Methods:

• Fabrication of a metallic optofluidic resonant cavity based on a symmetrical metal-cladding waveguide.
• Utilizing ultrahigh order modes (UOMs) for enhanced interaction between the gain medium and light.
• Pumping the cavity with a low-intensity continuous laser and measuring the lasing threshold.
• Employing Rhodamine 6G and methylene blue as gain media to validate the concept.

Main Results:

• Achieved continuous-wave lasing at room temperature with an ultralow pump threshold.
• Demonstrated effective pumping with low-intensity continuous lasers due to high Q and β factors.
• Observed lasing emission from the chip surface when pump laser is coupled into UOMs.
• Methylene blue exhibited lasing at a threshold as low as 2.1 μW/cm² at a concentration of 2.57*10⁻¹³ mol/ml.

Conclusions:

• The metallic optofluidic resonant cavity enables ultralow-threshold continuous-wave lasing.
• The symmetrical metal-cladding waveguide design effectively enhances light-gain medium interaction via UOMs.
• This technology holds promise for low-power photonic devices and sensors.