KEYWORDS: Random lasers, Neodymium, Beam path, Picosecond phenomena, Solid state lasers, Solid state physics, Near infrared, Laser crystals, Crystals, Absorption
This contribution presents a combined experimental and theoretical study on solid state random lasers in the visible (VIS) and near-infrared (NIR) domains operating in the diffusive regime under ultrafast pumping. NIR random lasers are based on Nd-doped crystal powders, while the VIS random laser is a ground powder of a Rhodamine B-doped hybrid compound incorporated into a di-ureasil host. A precise time-resolved analysis performed by using spatial filtering allows us to study the time evolution of local and spatially integrated random laser emissions. The study shows that the dynamics of both types of systems can be described by a similar rate equation model based on a statistical distribution of photon trajectories in an amplifying medium.
KEYWORDS: Neodymium, Random lasers, Picosecond phenomena, Beam path, Near infrared, Absorption, Spontaneous emission, Solid state physics, Solid state lasers, Absorbance
This work presents an accurate experimental comparison among the spectro-temporal performances of near infrared and visible emitting solid state random lasers under ultrafast pumping. The near infrared random lasers are based on stoichiometric Nd crystal powders whereas the visible random laser is a ground powder of a hybrid compound based on Rhodamine B incorporated into a di-ureasil host. We demonstrate that despite the different nature of the base materials, the spectro-temporal dynamics of both kind of systems can be described by a rate-equations model based on the photon paths in an amplifying medium with an exponential probability distribution.
The problem of light collection in random lasers (RLs) is addressed. As the radiation emitted by this system is Lambertian due to its spatial incoherence, a device based on an ellipsoidal revolution mirror is designed, developed, and tested in order to optimize the harvesting of the radiation emitted by the RL. The system provides a simple injection procedure of the emitted energy at the entrance of a multimode optical fiber. The results obtained show that the device has a net energy efficiency of 35%, close to the theoretically expected one.
This work presents a comparative study of the random lasing performance of several Nd-based stoichiometric compounds, including threshold and absolute slope efficiencies together with a discussion about the fundamental parameters which control the random laser operation in this kind of compounds.
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