Optical Microfluidic Waveguides and Solution Lasers of Colloidal Semiconductor Quantum Wells.

Area of Science:

• Optics and Photonics
• Materials Science
• Microfluidics

Background:

• High-quality lasers are essential for microfluidic devices, impacting sensors, flow cytometry, and lab-on-chip (LOC) technologies.
• Developing compact, efficient, and cost-effective coherent light sources for microfluidic applications remains a key challenge.

Purpose of the Study:

• To propose and demonstrate an ultralow-threshold microfluidic single-mode laser utilizing an on-chip cavity.
• To achieve in-solution lasing within a microfluidic device using colloidal semiconductor quantum wells (CQWs).

Main Methods:

• Fabrication of a microfluidic device using poly(dimethylsiloxane) (PDMS) with integrated SiO2-protected silver mirrors to form a Fabry-Pérot cavity.
• Dispersion of CdSe/CdS@CdₓZn₁₋ₓS core/crown@gradient-alloyed shell colloidal semiconductor quantum wells (CQWs) in toluene as the gain medium.
• Characterization of lasing performance, including optical gain and lasing thresholds.

Main Results:

• Demonstration of the first microfluidic laser utilizing CQW solution as the gain medium.
• Achieved record-low optical gain threshold of 17.1 µJ cm⁻² and lasing threshold of 68.4 µJ cm⁻² for solution-based lasing.
• Utilized air-stable, SiO2-protected silver films for highly tunable and reflective mirrors, forming a high-quality on-chip cavity.

Conclusions:

• The microfluidic CQW laser offers a compact, inexpensive, and high-performance coherent light source for microfluidics and integrated optics.
• The achieved record-low thresholds are attributed to the high-quality on-chip cavity and the unique properties of the core/crown@gradient-alloyed shell CQWs.
• This advancement paves the way for enhanced LOC devices and visible spectral region applications.