Robust Whispering-Gallery-Mode Microbubble Lasers from Colloidal Quantum Dots

Microlasers
hold great promise for the development of photonics and optoelectronics.
Among the discovered optical gain materials, colloidal quantum dots
(CQDs) have been recognized as the most appealing candidate due to
the facile emission tunability and solution processability. However,
to date, it is still challenging to develop CQD-based microlasers
with low cost yet high performance. Moreover, the poor long-term stability
of CQDs remains to be the most critical issue, which may block their
laser aspirations. Herein, we developed a unique but generic approach
to forming a novel type of a whispering-gallery-mode (WGM) microbubble
laser from the hybrid CQD/poly­(methyl methacrylate) (PMMA) nanocomposites.
The formation mechanism of the microbubbles was unraveled by recording
the drying process of the nanocomposite droplets. Interestingly, these
microbubbles naturally serve as the high-quality WGM laser resonators.
By simply changing the CQDs, the lasing emission can be tuned across
the whole visible spectral range. Importantly, these microbubble lasers
exhibit unprecedented long-term stability (over one year), sufficient
for practical applications. As a proof-of-concept, the potential of
water vapor sensing was demonstrated. Our results represent a significant
advance in microlasers based on the advantageous CQDs and may offer
new possibilities for photonics and optoelectronics.