Microscale lasers can be made by combining a gain medium with a periodic Bragg structure which serves as the resonator. A good example for such Bragg gratings are opaline geometries (pictured) obtained from the colloidal self-assembly of particles. While this method is cost- and time-saving, the obtained materials leave only little space for incorporation of the gain medium, resulting in very high laser thresholds.

Alexander Kuehne, Leibniz Institute for Interactive Materials, Aachen, Germany, and colleagues overcome this problem by using monodisperse polymer particles that serve as both gain medium and resonator. Starting from the two inexpensive commodity polymers diiododialkylfluorene and divinylbenzene, the researchers used a Heck-type dispersion polymerization to obtain monodisperse particles with adjustable diameter. Dispersions of these particles were then mixed with 1,2-bis(triethoxysilyl)ethane as a sol-gel precursor and loaded into an inkjet printer. Upon printing the solvents evaporated, and the self-assembled particles were encapsulated in the organo-silica matrix.

The team was able to print arrays (such as a QR code) that had features as small as 100 µm and showed single laser line emission upon pumping. The researchers underline the possibility to scale up the process and suggest it for the development of new technologies such as microdisplays, microlasers, and optical computation.

• Colloidal Crystal Lasers from Monodisperse Conjugated Polymer Particles via Bottom-Up Coassembly in a Sol–Gel Matrix,
  Annabel Mikosch, Sibel Ciftci, Alexander J. C. Kuehne,
  ACS Nano 2016.
  DOI: 10.1021/acsnano.6b05538