Appl. Phys. Lett. 101, 151101 (2012)

Shivakiran Bhaktha and colleagues from India and France have demonstrated a mirrorless optofluidic random laser. The device is based on a snake-shaped, dye-filled periodic microfluidic polydimethylsiloxane (PDMS) channel measuring 3 mm long, 28 μm deep and 10 μm thick, with a periodicity of 40 μm ± 0.65 μm. They fabricated the channel using soft lithography and filled it with an ethanolic dye solution. They used a stripe-shaped (3 mm long, 4 μm thick) beam from a Q-switched Nd:YAG laser at 532 nm to pump the dye circulating along the channel. Owing to the inherent disorder of the structure resulting from the limited accuracy of the photolithographic process, stimulated photons were multiply scattered at each PDMS–dye interface, thus resulting in random laser action when the losses were overcome. Random lasing was confirmed by the random change of the laser emission spectrum when different pump regions were scanned by the beam. Lasing was observed at a wavelength of 560 nm at a pump threshold power density of 80 μJ mm−2, which is comparable to conventional designs of optofluidic lasers. The researchers anticipate that the simplicity of their design may lead to the large-scale production of complex optofluidic structures.