If a fluorescence microscope’s resolution is set at 2 m, this technique can have 300 nm resolution — about a sixfold improvement over regular microscopes. (Credit: MIT)

Researchers have developed a new imaging technique that aims to illuminate cellular structures in deep tissue and other dense and opaque materials. The method uses tiny particles embedded in the material that give off laser light.

The team synthesized “laser particles” in the shape of tiny chopsticks, each measuring a small fraction of a human hair’s width. The particles are made from lead iodide perovskite — a material that efficiently absorbs and traps light. When the researchers shine a laser beam at the particles, the particles light up, giving off normal, diffuse fluorescent light. But if they tune the incoming laser’s power to a certain “lasing threshold,” the particles will instantly generate laser light.

The researchers were able to stimulate the particles to emit laser light, creating images at a resolution six times higher than that of current fluorescence-based microscopes. The new optical technique, named LAser particle Stimulated Emission (LASE) microscopy, could be used to image a particular layer of biological tissue. Theoretically, scientists could shine a laser beam into a three-dimensional sample of tissue embedded throughout with laser particles, and use a lens to focus the beam at a specific depth. Only those particles in the beam’s focus will absorb enough light or energy to turn on as lasers themselves.