ABSTRACT
Evidence is presented that a "three-for-one" process based on two cross-relaxations between Pr3+ ions efficiently populates the mid-infrared-emitting 3H5 manifold in a Pr3+-doped low-maximum-phonon-energy host. The concentration dependence of infrared fluorescence spectra and lifetimes of polycrystalline Pr:KPb2Cl5 initially excited to the 3F3,4 manifolds indicate that the 3500-5500-nm fluorescence becomes strongly favored over shorter-wavelength infrared emission bands in the higher-concentration sample. The strong concentration dependence of the 3F3 and 3H6 manifold lifetimes suggests that both of these decay by cross-relaxation processes, resulting in more than one ion excited to 3H5 for each ion initially excited to 3F3. Indeed, modeling and accounting for all possible decay paths indicate that, on average, about 2.3 ions are excited to 3H5 for each initially-excited ion. This confirms that the three-for-one excitation process must occur and contribute significantly to the total excitation efficiency. These results indicate that the two distinct cross-relaxation processes observed between Pr ions result in substantially higher excitation quantum efficiency, 230%, than any ever reported in rare-earth doped materials.
ABSTRACT
We present an erratum regarding the contents of Table 1.
ABSTRACT
The temperature dependence of the absorption, fluorescence, and fluorescence lifetimes of states relevant to short-wave-infrared and mid-infrared laser operation have been measured in Pr:RbPb2Cl5. The 3600-5500-nm fluorescence grows strongly with temperature, and at room temperature represents the large majority of the observed photon flux. Intra-ionic decay processes cannot explain this dominance, but a combination of two cross-relaxation processes provides good agreement with the data. These results indicate a three-for-one process: the excitation of nearly three ions to the 3H5 manifold of Pr3+ by each one initially excited to 3F3, with the potential for exceptionally high efficiency excitation of mid-infrared laser materials.
ABSTRACT
Mid-infrared, solid-state laser materials face three main challenges: (1) need to dissipate heat generated in lasing; (2) luminescence quenching by multiphonon relaxation; and (3) trade-off in high thermal conductivity and small maximum phonon energy. We are tackling these challenges by synthesizing a ceramic nanocomposite in which multiple phases will be incorporated into the same structure. The undoped majority species, MgO, will be the main carrier of high thermal conductivity, and the minority species, Er:Y2O3, will have low maximum phonon energy. There is also an inherent challenge in attempting to make a translucent part from a mixture of two different materials with two different indexes of refraction. A simple, co-precipitation technique has been developed in which both components are synthesized in situ to obtain intimate mixing. These powders compare well to commercially available ceramics, including their erbium spectroscopy, even when mixed as a composite, and can be air-fired to â¼96% of theoretical density, yielding translucent parts. As the amount of Er:Y2O3 increases, the translucency decreases as the number of scattering sites start to coalesce into large patches. If the amount of Er:Y2O3 is sufficiently small and dispersed, the yttria grains will be pinned as individuals in a sea of MgO, leading to optimal translucency.
ABSTRACT
We report what is believed to be the first laser operation based on Ho3+-doped Y2O3. The Ho3+:Y2O3 ceramic was resonantly diode-pumped at ~1.93 µm to produce up to 2.5 W of continuous wave (CW) output power at ~2.12 µm. The laser had a slope efficiency of ~35% with respect to absorbed power and a beam propagation factor of M2 ~1.1. We have measured the absorption and stimulated emission cross sections of Ho3+:Y2O3 at 77 K and 300 K and present the calculated gain cross section spectrum at 77 K for different excited state inversion levels.
ABSTRACT
We report the laser performance of resonantly diode-pumped Er:YAG from liquid nitrogen temperature to above room temperature. Relative to incident pump power, the best performance was observed at approximately 160 K. Spectroscopy and modeling show that this is due primarily to the changing efficiency of diode pump absorption as the absorption lines broaden with temperature. However, the physics of the Er:YAG system indicates that even with arbitrarily narrow pump linewidth the most efficient laser performance should occur at a temperature somewhat above 77 K. The causes of the temperature dependence are at least qualitatively understood.
Subject(s)
Lasers, Solid-State , Cold Temperature , Computer-Aided Design , Equipment Design , Equipment Failure Analysis , Reproducibility of Results , Sensitivity and Specificity , TemperatureABSTRACT
Resonantly pumped Er(3+):Sc(2)O(3) laser operation is achieved with a quantum defect (QD) of 1.5% at liquid nitrogen temperature. The laser, in-line pumped at 1535 nm, operated at 1558 nm with a slope efficiency of over 45%. This is believed to be the lowest QD eye-safe laser ever reported. CW output of over 3.3 W was obtained in this first experiment.
ABSTRACT
We have studied the concentration dependent fluorescence decay kinetics of ceramic Nd:YAG, to resolve inconsistencies in the previous literature. Our data indicate that earlier reports of single exponential lifetimes even at Nd concentrations of a few percent were due to the effects of long-pulse excitation. Under short-pulse excitation the fluorescence decay is nonexponential for concentrations greater than about 1% atomic. Energy migration to sinks consisting of cross-relaxing Nd ions dominates at long times, whereas single-step energy transfer to randomly distributed quenching sites dominates at earlier times. The concentration dependence of this single-step transfer indicates direct cross-relaxation between individual ions at concentrations below 4% atomic, but resonant transfer to quenching sites consisting of Nd pairs at higher concentrations.
ABSTRACT
We report what is believed to be the first observation of phase conjugation by stimulated Brillouin scattering (SBS) in TeO2 single crystal. The observed very low threshold for phase-conjugate mirror (PCM) formation, high PCM reflectivities in this initial experiment, and commercial availability of material hold promise for a host of practical applications in the near future. The resultant steady-state gain parameter, approximately 100 cm/GW, is to our knowledge the largest ever reported for any SBS material.
