(follow this lecture in Spanish)
A conventional laser is made of an active homogenous material, which is for excited either electrically or optically (here shown by the green laser) and that emits light via the stimulated emission process. The pumped area is the yellow stripe (yellow because of the sum of green and red) and the red lasing emission is the horizontal red line.
A random laser is a system formed by a random assembly of elastic scatters dispersed into an optical gain medium. The multiple light scattering replaces the standard optical cavity of traditional lasers and the interplay between gain and scattering determines its unique properties. Usually a random medium consists of irregularly shaped scatters, with some average scattering strength that is constant over the frequency window of the laser.
Artistic view of a Random Laser
Unlike ordinary laser, the resulting light emission is multidirectional and not really monochromatic, but the threshold behavior, the photon statistics and relaxation oscillations are very similar to those of standard lasers.
Resonance driven random lasing
We have studied the case where the scattering is resonant. Our system can sustain scattering resonances over the gain frequency window, since it is formed by monodisperse spheres randomly assembled. The unique resonant scattering of this material allows to control the laser emission via the diameter of the particles and their refractive index. Our system is the first example of random device with a priori designed lasing peak within the gain curve.
This is a sketch of the random mode profile of a small photonic glass. The image show the field speckle inside the system, which is the modal structure behind the lasing process.
Random lasing from a Photonic Glass
A photonic glass with DCM dye infiltrated.
Photonic glass random laser