Synopsis: Shaking Up a Grain-Based Laser

A random laser formed from shaken grains can be partially manipulated by varying the amount of shaking, according to new experiments.
Synopsis figure
V. Folli et al., Phys. Rev. Lett. (2012)

Laser light can be generated from randomly ordered materials, but so far the randomness has been fixed. Now, researchers have produced laser light by shaking a box of grains. Viola Folli of the Sapienza University of Rome, Italy, and her collaborators were able to alter the laser spectrum by varying the shaking intensity. The experiments, described in Physical Review Letters, may open a new realm of mechanically controlled photonic devices.

Random lasers don’t match our cartoon picture of a laser having a long cavity for collimating the beam. Instead, these unorthodox lasers are made of powders, colloids, and other disordered assortments that scatter light multiple times in different directions, while an accompanying gain medium provides the amplification. The scattering elements have typically been too small for mechanical manipulation, but granular materials could offer some “control” over the random configurations. In particular, grains can switch from a solidlike to gaslike state when shaken sufficiently hard.

Folli and her colleagues wanted to explore whether grain dynamics could lead to novel optical effects. They started with millimeter-sized metallic spheres and immersed about 1500 of them in a fluorescent dye (the gain medium). A vibrating plate shook the grains from beneath, while an external laser provided optical stimulation. The emitted light showed a peak at 600 nanometers, which was due to random lasing but controlled by the vibrational motion. In addition, when the shaking reached a certain magnitude, a second peak appeared around 620 nanometers. The authors claim this additional lasing arises from a few grains forming a short-lived cavity within the dynamic system. – Michael Schirber


Announcements

More Announcements »

Subject Areas

OpticsSoft Matter

Previous Synopsis

Next Synopsis

Atomic and Molecular Physics

Turning the Optomechanical Tables

Read More »

Related Articles

Synopsis: Starting Fluid for Laser Fusion
Energy Research

Synopsis: Starting Fluid for Laser Fusion

A laser-based fusion experiment demonstrates that liquid fuel capsules could rectify problems encountered with ice-based fuel capsules. Read More »

Synopsis: Graphene’s Elegant Optics Explained
Graphene

Synopsis: Graphene’s Elegant Optics Explained

Theoretical calculations anchor graphene’s simple optical absorption in its two-dimensional structure instead of its cone-shaped energy bands. Read More »

Synopsis: Sharper Vision for Infrared Telescopes
Optics

Synopsis: Sharper Vision for Infrared Telescopes

Converting infrared light to visible light might boost the sensitivity of infrared telescope arrays. Read More »

More Articles