RESUMEN
In this Letter, we theoretically analyze cavity beam propagation in a gain medium and cavity using the rate equation and generalized Huygens integral, respectively. Spontaneous chaos and extreme events (EEs) occurred around the transverse-mode-degenerate cavity configuration because of transverse-mode competition. A closed occurrence region relating to varying pump power and cavity length was observed. The experimental results in a continuous-wave Nd:YVO4 laser agreed with the aforementioned numerical results. Because gain effect is essential to a laser, we assume that EEs can be intrinsic and universal in a well-aligned laser system if it satisfies the specific transverse-mode competition.
RESUMEN
We experimentally and numerically investigate amplified spontaneous emission (ASE) in the presence of radiation reabsorption by using an end-pumped ruby laser. From the fluorescence time decay in the axial direction, we find that the average path length of ASE is much larger than the reabsorption length and exhibits sharp variation near the semi-concentric cavity configuration; however, the side lifetime is independent of cavity configuration. In addition, an axial power bump corresponding to a side power valley and the enhanced fluorescence R-line spectrum are observed and explained.
RESUMEN
In this study, we take the pump rate into consideration for the first time to give a theoretical description of radiation trapping in three-level systems. We numerically verify that under strong pumping, the population of the ground state is depleted, which leads to saturation of the radiation trapping within the pumped region. This saturation inevitably clamps the lifetime lengthening that is experimentally verified on a 0.05 at% thin ruby crystal based on the axial pinhole method. Our model is confirmed to be valid in lifetime measurement when the ruby fluorescence is collected from both the pumped and the unpumped regions.
RESUMEN
We study both numerically and experimentally a specific geometric mode, named VW mode, in an end-pumped Nd:YVO4 laser with a plano-concave cavity near the 1/3-degeneracy. Three theoretical methods are used to analyze the transverse profiles, the operator method [J. Opt. Soc. Am. A 22, 1559 (2005)], the SU(2) wave representation [Phys. Rev. A 69, 053807 (2004)], and the Fox-Li approach. Some differences among them are addressed and clarified. Moreover, the generating conditions for VW mode are found peculiar and its propagation character is demonstrated. By comparing the experimental mode patterns with the three numerical results, we conclude that the field of a geometric mode in the operator method should be extended to include those of the reverse directional trajectories and the SU(2) coherent state representation is found too specific to produce the fringes within some transverse patterns.
RESUMEN
This work investigates the optical Kerr property of azo-dye doped nematic liquid crystal films using the biphotonic Z-scan technique. The results indicate that the nonlinear effect measured using the Z-scan technique with a red light can be modulated or switched with the simultaneous application of a green light, because of photoisomerization and thermal effects, as determined by dynamic measurements. The former dominates in the early stage when the green light is applied, while the latter dominates in the later stage.
RESUMEN
We demonstrate that a laser beam converging from a specific transverse mode is a bottle beam, as described in J. Opt. Soc. Am. B 20, 1220 (2003). To our knowledge, this is the first time that a bottle beam has been generated directly from a laser. By calculating the radiation forces on a dielectric Rayleigh sphere in the bottle beam, we show that the single beam can trap high-refractive-index particles at the multiple axial sites of intensity maxima, and it can confine low-index particles on a transverse plane within the bottle regions. Such a novel laser beam may have other applications.
RESUMEN
We demonstrate that various optical bottle beams can be directly generated from a tightly focused end-pumped Nd:YVO4 laser. By controlling the size of pump beam and intracavity aperture in a planoconcave cavity, we obtain well contrasting optical bottles with semiconfocal, 1/3-, and 1/5-degenerate cavity configurations. These beams result, respectively, from the superposition of the fundamental mode and the corresponding lowest degenerate transverse eigenmode, which is in-phase at their beam waists. Unlike that of our previous simulation model, this new observation is universal; it is suitable for any kind of gain media in tightly end-pumped lasers.
