If it were possible, a flexible laser could work with even the slightest variations in the natural world. However, because they are inherently unstable, lasers composed entirely of liquids have proven successful in maintaining continuous operation under ambient conditions only if they are encapsulated in a specially designed container or matrix to prevent the liquid from evaporating.

In a new study, scientists at the University of Tsukuba demonstrated a simple method to form a self-contained spherical microlaser made entirely of liquid that works stably even below the atmosphere. They have developed a tunable laser that can be inkjet printed and has a color that changes based on its shape.

The microdroplets used in the method act like flexible, durable and pneumatically tunable lasers. This new development could make it possible to create lasers that can be used in normal environments, unlike today’s “drip lasers”, which cannot function below the atmosphere.

Scientists have used an artificial lotus effect to create liquid droplets that can act like lasers and remain stable for up to a month. The ‘drip lasers’ currently available cannot be used under ambient conditions as they simply vaporize unless enclosed in a container.

In this recent study, a laser-enabled dye was added to an ionic liquid called 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF4). This particular liquid was chosen for its very high surface tension and sustained evaporation rate. To make a quartz substrate impermeable to liquids, tiny nanoparticles of fluorinated silica are then deposited on the material. The small droplets of EMIBF4 applied with a pipette remain almost completely spherical. The drop could maintain its stability for at least 30 days, the results revealed.

First author Professor Hiroshi Yamagishi said: “The desirable morphological and optical properties of the droplet were predicted by mathematical calculations to persist even when exposed to gas convection.”

When excited with a laser pump source, the droplet can maintain an optical resonance due to its shape and resistance to vaporization. By gently altering droplet morphology, blowing nitrogen gas can modify laser peaks in the 645-662 nm region.

Professor Yamagishi said: “This is, to our knowledge, the first liquid laser oscillator that is reversibly tunable by the gas convections.”

“The laser droplet can also be used as a highly sensitive humidity sensor or airflow detector. The researchers then used a commercial inkjet printing device equipped with a printer head that could work with a viscous liquid. The printed arrays of laser droplets worked without further treatment.”

“The findings of this study indicate that the production is highly scalable and easy to perform, so it can be easily applied to manufacture low-cost sensor or optical communication devices. This research can lead to new air flow detectors or cheaper fiber optic communication.”

Magazine reference:

  1. Hiroshi Yamagishi et al. Pneumatically Adjustable Drop Microlaser. Reviews on laser and photonics. DOI: 10.1002/lpor.202200874