Researchers at the Tsukuba Energy Materials Science Research Center at the University of Tsukuba in Japan have successfully demonstrated a new method for producing ionic liquid microdroplets that can be used as flexible, durable and aerodynamically tunable lasers.
Existing droplet lasers are unable to operate under ambient conditions without evaporating, and the new development may enable the lasers to be used in everyday environments, the scientists said. This may help in the development of new airflow detectors or more flexible and less expensive optical detectors Communication devices.
The artificial lotus effect is being used to create droplets that can act like lasers while remaining stable for up to a month. This replicates the self-cleaning properties of the lotus flower: thanks to tiny protrusions on the leaves, the droplets are able to form near-perfect spheres and roll off, taking dust with them.
The researchers chose the ionic liquid 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4) because of its slow evaporation properties and relatively high surface tension. This liquid is mixed with a dye to make a laser. Then, tiny fluorinated silica nanoparticles are coated on the quartz substrate, allowing the surface to repel the liquid. When EMIBF4 was deposited on it from the pipette, the tiny droplets were almost completely spherical. The researchers demonstrated that the droplets could remain stable for at least 30 days.
The droplet's shape and stability allow it to maintain optical resonance when excited by a laser pump source. Blown nitrogen can move the laser peak in the 645 to 662 nm range by slightly distorting the droplet shape. It can also be used as a very sensitive humidity sensor or airflow detector.
Using a commercial inkjet printing device with a print head that can work with viscous liquids. The team found that the printed laser droplet array could function without further processing. They say their findings show that production is highly scalable and easy to perform, so it can be easily applied to make inexpensive sensors or optical communication devices. The study was published in the Review of Lasers and Photonics.
First author Prof. Hiroshi Yamagishi explains, "Mathematical calculations predict that the desired morphology and optical properties of the droplet can be maintained even when exposed to gas convection. To our knowledge, this is the first liquid laser oscillator that can be reversibly tuned by a gas to convection."
