Nanowire lasers have attracted increasing interest for low-power-consuming and ultrasmall photonic devices. Following extensive research with semiconductor materials, an alternative approach to nanowire lasers has been developed using organic molecules. Their self-assembly properties and compatibility with flexible platforms make these organic materials promising.

Hisao Yanagi, Nara Institute of Science and Technology (NAIST), Japan, and colleagues have developed a method for fabricating organic nanowires with controlled lengths. Both p-type and n-type semiconducting thiophene/phenylene co-oligomers (TPCOs) were deposited onto a cleaved potassium chloride surface by a mask-shadowing technique. The materials grew in epitaxially oriented nanowires with lengths ranging from 5 to 100 µm (pictured), depending on the positions of the mask holes.

Under optical pumping, isolated single nanowires demonstrated axial Fabry-Pérot lasing, i.e., they act like a laser oscillator in which two mirrors are separated by an amplifying medium. Their lasing threshold fluence (the optical energy per unit area) was reduced with increasing nanowire lengths, which is in accordance with theoretical analysis considering emission cross-section and loss parameters. The nanowire lasing in both p- and n-type molecular semiconductors could lead to the fabrication of organic nanowire diode lasers.

• Organic Nanowire Lasers with Epitaxially Grown Crystals of Semiconducting Oligomers,
  Kazuki Torii, Tetsuya Higuchi, Kei Mizuno, Kazuki Bando, Kenichi Yamashita, Fumio Sasaki, Hisao Yanagi,
  ChemNanoMat 2017.
  DOI: 10.1002/cnma.201700137