Random Laser Action in Nd:YAG Crystal Powder.

This work explores the room temperature random stimulated emission at 1.064 µm of a Nd:YAG crystal powder (Neodymium-doped yttrium aluminum garnet) in a very simple pump configuration with no assistance from an internal mirror. The laser threshold energy as a function of pump beam area and pump wavelength has been measured, as well as the temporal dynamics of emission pulses. The absolute energy of stimulated emission and the absolute laser slope efficiency have been measured by using a method proposed by the authors. The results show a surprising high efficiency that takes the low Nd3+ ion concentration of the crystal powder into account.

Diffusive random laser modes under a spatiotemporal scope.

At present the prediction and characterization of the emission output of a diffusive random laser remains a challenge, despite the variety of investigated materials and theoretical interpretations given up to now. Here, a new mode selection method, based on spatial filtering and ultrafast detection, which allows to separate individual lasing modes and follow their temporal evolution is presented. In particular, the work explores the random laser behavior of a ground powder of an organic-inorganic hybrid compound based on Rhodamine B incorporated into a di-ureasil host. The experimental approach gives direct access to the mode structure and dynamics, shows clear modal relaxation oscillations, and illustrates the lasing modes stochastic behavior of this diffusive scattering system. The effect of the excitation energy on its modal density is also investigated. Finally, imaging measurements reveal the dominant role of diffusion over amplification processes in this kind of unconventional lasers.

Laser action in Nd(3+)-doped lanthanum oxysulfide powders.

We have investigated the stimulated emission properties of Nd(3+) doped La(2)O(2)S powders at room temperature as a function of pumping energy density, excitation wavelength, and Nd(3+) ion concentration. The absolute stimulated emission energy has been measured. Expressions for the slope efficiencies and lasing thresholds as a function of rare earth concentration and pumping wavelengths, which qualitatively agree with experimental observations, are discussed.

A self-tunable Titanium Sapphire laser by rotating a set of parallel plates of active material.

In a recent work, the authors reported the experimental demonstration of wavelength tuning in a single birefringent plate of Ti:sapphire crystal based on its own birefringence properties. In that device, the thickness of the active plate, limited by the width of the single order tuning spectral region, imposed a strong constraint in the power performance of the laser. The aim of this work is to overcome this limitation by using a set of several identical birefringent plates so that the wavelength tuning of the laser is obtained by synchronously rotating the plates in their own plane. A discussion about the laser performance is presented.

Broadband laser tunability of Nd3+ ions in 0.8CaSiO3-0.2Ca3(PO4)2 eutectic glass.

Site-selective spectroscopy and stimulated emission experiments performed in the (4)F(3/2)-->(4)I(11/2) laser transition of Nd(3+)-doped 0.8CaSiO(3-) 0.2Ca(3)(PO(4))(2) eutectic glass are presented. The spectral features of the excitation spectra and those of spontaneous and stimulated emissions reveal the existence of a very complex crystal field site distribution for Nd(3+) ions. As a consequence, the stimulated emission of Nd(3+) in this glass shows a tunability of about 10 nm as a function of excitation wavelength.

Wavelength tuning of Titanium Sapphire Laser by its own crystal birefringence.

We report for the first time to our knowledge an experimental demonstration of wavelength tuning in a broadband-emitting Ti: sapphire laser crystal based on its own birefringence properties. To investigate the tuning characteristics of the spectral filter, we have used Jones-Vector formalism. The calculated wavelength-selective tuning matches very precisely the experimental observations.

K5Nd(MoO4)4: a self-tunable laser crystal.

We report for the first time to our knowledge an experimental demonstration of wavelength self-tuning in a K5Nd(MoO4)4 broadband-emitting laser crystal (KNM), as well as a theoretical treatment of the system based on its birefringence properties. The self-frequency-tuning of the laser along the full spectral range of the KNM crystal was obtained by rotating a birefringent gain plate in its own plane. The gain plate was placed inside a resonator at Brewster's angle. The tuning characteristics of the spectral filter were obtained by use of the Jones vector formalism. The calculated wavelength-selective tuning precisely matches the experimental observations.